77/57 


HANDBOOK   ON   ENGINEERING 


PUBLISHERS     OF     BOOKS      F  O  R^ 

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Electrical  World  v  Engineering  News -Record 
American  Machinist  v  Ingenierfa  Internacional 
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Chemical  6  Metallurgical  Engineering 
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HANDBOOK  ON 

ENGINEERING 

THE  PRACTICAL  CARE  AND  MANAGEMENT 


OF 


DYNAMOS,     MOTORS,    BOILERS,    ENGINES,    PUMPS, 
INSPIRATORS  AND  INJECTORS,  REFRIGERATING 
MACHINERY,  HYDRAULIC  ELEVATORS,  ELEC- 
TRIC ELEVATORS,  AIR  COMPRESSORS,  ROPE 
TRANSMISSION    AND    ALL    BRANCHES1 
OF  STEAM  ENGINEERING. 


BY 

HENRY  C.  TULLEY, 
Engineer  and  Member  Board  of  Engineers,  St.  Louis. 


SIXTH  EDITION— SIXTH  IMPRESSION 
Revised  and  Enlarged 

McGRAW-HILL  BOOK  COMPANY,  INC;. 
239  WEST  39TH  STREET.     NEW  YORK 

LONDON:  HILL  PUBLISHING  CO.,  LTD. 
6  &  8  BOUVERIE  ST.,  B.  C. 


Entered  according  to  Act  of  Congress,  in  the  year  1900,  by 

HENEY  C.  TULLEY, 
In  the  Office  of  the  Librarian  of  Congress,  at  Washington. 


Copyrighted,  1907. 


INTRODUCTION. 

The  object  of  the  Author  in  preparing  this  work  has  been  to 
present  to  the  practical  engineer  a  book  to  which  he  can,  with 
confidence,  refer  to  for  information  regarding  every  branch  of 
his  profession. 

Up  to  the  date  of  the  publication  of  this  book,  it  was  impossi- 
ble to  find  a  plain  and  practical  treatise  on  the  steam  boiler,  steam 
pump,  steam  engine,  and  dynamo,  and  how  to  care  for  them; 
electric  and  hydraulic  elevators,  and  how  to  care  for  them ;  and 
all  other  work  that  an  engineer  is  apt  to  come  in  contact  with  in 
his  profession. 

An  experience  of  over  twenty-five  years  with  all  kinds  of  en- 
gines and  uoilers,  pumps,  and  all  other  kinds  of  machinery,  ena- 
bles the  Author  to  fully  understand  the  kind  of  information  most 
needed  by  men  having  charge  of  steam  engines  of  every  descrip- 
tion, and  what  they  should  comprehend  and  employ. 

With  this  object  in  view,  the  Author  has  carefully  made  note  of 
his  past  experience,  and  has  also  made  note  of  things  that  came 
to  his  notice  while  visiting  different  engine  rooms,  and  accord- 
ingly, has  taken  up  each  subject  singly,  excluding  therefrom, 
everything  not  strictly  connected  with  steam  engineering. 

Particular  attention  has  been  given  to  the  latest  improvements 
in  all  classes  of  steam  engines,  with  rules  and  formulas  ac- 
cording to  the  best  modern  practice,  which,  it  is  hoped,  will  be 
of  great  value  to  engineers,  as  nothing  of  the  kind  has  heretofore 
been  published. 

This  book  also  contains  ample  instructions  for  setting  up,  lining, 
reversing  and  setting  the  valves  of  all  classes  of  engines. 

THE  AUTHOR. 


IV? 


on) 


CONTENTS. 


For  Alphabetical  Index  to  Subjects,  see  page  963. 


CHAPTER  I. 

PAGE 

THE     ELEMENTARY     PRINCIPLES     OF    ELECTRICAL    MA- 

CHINERY j 

A  permanent  magnet 1  to  2 

Two-bar  magnet 3  to  6 

A  magnet  needle 3 

Magnetic  lines  of  force 6 

Lines  of  force 6  to  14 

Magnetic  force 13 

To  find  the  lifting  capacity  of  a  magnet 13 

CHAPTER  II. 

THE  PRINCIPLES  OF  ELECTROMAGNETIC  INDUCTION    14  to  22 
The  armature  cores 23  to  27 


CHAPTER  III. 

TWO-POLE  GENERATORS  AND  MOTORS  ........  27 

The  simplest  type  of  armature  winding 27  to  29 

Two-pole  generators  and  motors 27  to  30 

The  general  arrangement  of  the  field  and  armature  in  a  two-pole 

machine  33  to  36 

The  reason  why  brushes  are  set  differently  on  motors  than  on 

dynamos 36  to  37 

v 


VI  CONTENTS. 

CHAPTER  IV. 

PAGE, 

MULTIPOLAR  MACHINES 38 

Multipolar  machines 38  to  39 

Setting  the  brushes  on  a  four-pole  machine 40 

Setting  the  brushes  on  an  eight-pole  machine 41 

The  lap  and  wave  winding  for  four-pole  machine*   .     .     .     .     .    42  to  46 

CHAPTER  V. 

SWITCH    BOARD,  DISTRIBUTING    CIRCUITS,  AND  SWITCH 

BOARD  INSTRUMENTS 47 

Generators  of  the  constant  potential  type 47  to  48 

The    switch-board    arranged    for     two  generators  of    the    shunt 

type 49  to  54 

Switch-board  for  three-wire  system 56  to  57 

To  wire  a  large  building  with  a  lighting  and  power  system       .    58  to  60 

The  ammeter       60 

Circuit  breakers 62  to  63 

The  electromotive  force  in  volts,  etc 63 

CHAPTER  VI. 

ELECTRIC  MOTORS 64 

Motors  and  their  connections 64  to  73 

The  strength  of  an  electric  current,  etc 73 

The  watt 73 

The  ampere 73 

Candle  power 73 

CHAPTER  VII. 

INSTRUCTIONS  FOR  INSTALLING  AND  OPERATING  SLOW 

AND  MODERATE  SPEED  GENERATORS  AND  MOTORS     .     .  74 

To  remove  the  armature 74 

Assembling  the  parts 74 

Filling  the  bearings 74 

To  complete  the  assembly 74 

Starting 74 

Care  of  commutator 75 


CONTENTS.  yj| 

If  commutator  gives  trouble * 

General  directions  for  starting  dynamos     .  7fi 

Bringing  dynamos  to  full  speed     .     .     . '  77 

Connecting  one  dynamo  with  another 78 

Switching  dynamos  into  circuit 7g 

How  dynamos  may  be  connected  together 

Dynamos  in  parallel 7g 

Directions  for  running  dynamos  and  motors 80 

Precautions  in  running  dynamos    .     .    - 81 

Personal  safety '.    .    .    ,          ,81 

CHAPTER  VIII. 

WHY  COMMUTATOR  BRUSHES  SPARK  AND  WHY  THEY  DO 

NOT  SPARK 82  to  84 

The  way  in  which  the  current  is  shifted,  etc 84,  85 

Diagram  illustrating  the  same 85 

If  the  commutated  coil,  etc 86 

Even  when  the  machine  is  properly  proportioned,  etc 87 

Sparking 87  to  91 

Noise - 91  to  92 

Heating  in  dynamo  or  motor 93  to  94 

The  effect  of  the  displacement  of  the  armature 94  to  98 

Table  of  carrying  capacity  of  wires 99,  101 

Insulation  resistance 100 

Soldering  fluid 101 

Table  showing  the  size  of  wire  of  different  metals  that  will  be  melted 
by  currents  of  various  strengths     .         102 

CHAPTER  IX. 

INSTRUCTIONS    FOR    INSTALLING  AND  OPERATING  APPA- 
RATUS FOR  ARC  LIGHTING. 

Brush  arc  light  generator    .     .     .     .     .     0 .     .     10* 

Multiple  circuit  Brush  arc  generator    .     .     .     0 105 

Armature  circuits  of  Brush  machine     ..,     0     ....     o    ...     106 

Diagram  of  multiple  circuits .    «.    ....     107 

Current  regulator  for  Brush  arc  generator    .     ,    .    .    .    .    .    »    . 
Position  of  brushes  on  arc  lighting  generator ,109 


Vlll  CONTENTS. 

PAGE. 

Setting  brushes  of  arc  light  generator 110 

Care  of  the  commutator  and  brushes Ill 

Series  system  of  arc  lighting 112 

Transformers  for  series  system , 113 

General  Electric  Co.'s  transformer 114 

Operation  of  transformer,  series  system 115 

Sizes  of  General  Electric  transformers 116 

Switchboards  for  arc  lighting  apparatus 117 

General  Electric  Co.'s  switchboards ,     ...  118 

Switchboard  for  Westinghouse  system 119 

Westinghouse  transformers,  series  system 120 

Western  Electric  Co.'s  regulator 121 

Regulator  for  constant  current  series  system    .     .    * 122 

Adams-Bagnall  regulator 123 

Fort  Wayne  Electric  Co.'s  regulator 124 

General  arrangement  of  Fort  Wayne  circuits 125 

Fort  Wayne  system  of  arc  lighting , 126 

Alternating  current,  constant  current  circuits 127 

General  Electric  Co.'s  enclosed  arc  lamp 128 

Westinghouse  lamp 129 

Lamp  for  series  alternating  current  circuits 130 

Fort  Wayne  lamp 131 


CHAPTER  X. 

Western  Electric  Co.'s  lamp 132 

Actuating  clutches  for  enclosed  lamps 133 

Westinghouse,  Western  Electric  and  Fort  Wayne  clutches     .     .     .  134 

Carbon  holders .  1 35 

Enclosed  direct  current  lamps 136 

General  Electric  Go's,  lamp 137 

Voltage  of  General  Electric  Co.'s  lamp 138 

Westinghouse  and  Fort  Wayne  enclosed  lamps 139 

Fort  Wayne  lamp  for  direct  current  circuits 140 

Enclosed  lamps  for  power  circuits 141 

Construction  and  operation  of  enclosed  lamps       142 

Series  arc  lamps  for  power  circuits 143 


CONTENTS. 


Westinghouse  direct  current  enclosed  lamp 

Cut-out  for  General  Electric  lamp    , 

Constant  potential  enclosed  lamps 

Fort  Wayne  constant  potential  lamp    ...'.'.' 

Westinghouse  lamp    .     .     ..... 

General  Electric  Co.'s  lamp     .     . 

Fort  Wayne  street  lighting  system  ...... 

Lamp  used  with  Fort  Wayne  system    ,  151 

Luminous  or  flaming  arc  lamp    ,    .     .     .....  152 

The  Excello  lamp       •     '••...,.,..'."- 

Excello  lamp  for  direct  current  .    .     .     .  154 

Life  of  carbons  in  the  Excello  lamp    ....... 

Directions  for  care  of  lamps    ...........  156 

How  to  trim  lamps     .     .....     .......  157 

Care  of  dashpot  and  globes    „     ......    .  153 

How  to  install  arc  lamps    ,     .......    .    e  150 

CHAPTER  Xa. 

INCANDESCENT  WIRING  TABLES        .......     161  to  162 

Amperes  per  motor,  table  ..............     169,170 

Volts  lost  at  different  per  cent  drop  ..........     171,  172 

Amperes  per  lamp,table    ................  173 

Approximate  weight  of  "  O.  K."  triple  braided  weatherproof  copper 

wire    ......................  174 

Table  showing  difference  between  wire  gauges  in  decimal  parts  of  an 

inch     ......................  175 

Electric  light  conductors,  table  ......  ......  .  .  176 

CHAPTER  XI. 

THE  STEAM  ENGINE   ............     ....  177 

The  selection  of  an  engine     ...............  177 

The  gaia  by  expansion      .........    ••    ......  183 

Table  of  cut-off  in  parts  of  the  stroke    .     .     .........  183 

The  steam  engine  governor  ............  183  a»d  1J 

The  fly-wheel  ....................  184 

Horse  power  ....................  *' 

Care  and  management  of  a  steam  engine    .    „    ........  185 


X  CONTENTS. 

PAGE. 

Lubrication  of  an  engine 186 

Selecting  an  oil  for  an  engine 187 

The  piston  packing 187 

Crank-pins ,     .  188 

Connecting  rod  brasses 189 

Knocking  in  engines 189  to  190 

The  main  bearings '.     .     .     .     190  to  192 

Repairs  of  engines 191 

Fitting  a  slide  valve 191 

Eccentric  straps 192 

Heating  of  journals 193 

Automatic  engines 194 

To  find  the  dead  centers  .     .     .     .     • 195 

View  of  tandem  compound  engine  and  its  foundation 198 

How  to  line  an  engine 199  to  203 

View  of  twin  tandem  compound  engine,   showing  arrangement  of 
piping 200 

CHAPTER  XIa. 

Directions  for  setting  up,  adjusting  and  running  the  improved  Cor- 
liss steam  engine 205 

Adjustment  of  Corliss  valve  gear  with  single  and  double  eccentrics.  206 

Adjustment  with  two  eccentrics     .• 215 

The  compound  engine 222 

Horse  power  of  compound  engine 232 

Condensing  engines 232 

Condensers 235  to  253 

Setting  the  piston  type  of  valve 261 

Setting  the  cut-off  valve  .     . 266 

Flat  valve  riding  cut- off .'     ...  268 

Starting  and  running  a  compound  engine 253 

.       CHAPTER  XII. 

THE  STEAM  ENGINE  —  CONTINUED 274 

What  is  work 274 

What  is  power 274 

Horse  power,  stroke  and  weights  of  engine 273,275 

General  proportions  of  engine 275 


CONTENTS.  xj 

Rules  for  weights  of  fly-wheels    ......  AGE* 

View  of  the  Russell  engine        ...... 

Setting  the  valves  of  Russell  engines    .....  277 

View  of  the  Porter-Allen  engine    ...... 

Description  of  the  Porter-Allen  engine  ......     '  282-287 

Directions   for    setting   the  valves,    and  running  the  Porter-Allen 


...................    271,288 

The  Porter  governor    ............  289 

The  Armington  and  Sims  engine    ......  *  290* 

Setting  the  valve  in  an  Armington  and  Sims  engine     .     .  290 

The  Harrisburg  engine      .........  291 

The  care  and  management  of  the  Harrisburg  engine    .     .  291-296 

The  Mclntosh  and  Seymour  high  speed  engine       .     .  296 

How  to  set  the  valves  of  an  M.  and  S.  engine      .....  296 

The  Ideal  engine      ...........     .  298 

Instructions  for  starting  and  operating  Ideal  engines  ....     298-306 

Instructions  for  indicating  Ideal  engines    ..........  306 

The  Westinghouse  compound  engine     ........  .  308 

Westinghouse  compound.,  diagram  of  cylinders  ........  309 

How  to  set  the  valve  on  a  Westinghouse  engine      .......  307 

Some  points  on  cylinder  lubrication   ............  309 

Automatic  lubricators       ........     ......    310,312 

Setting  a  plain  slide  valve  with  link  motion     .......    313,  318 

Valve  setting  for  engineers  ......   ;*>  ......    318,322 

View  of  a  slide  valve  engine  showing  the  point  of  taking  steam    .    .321 
View  of  a  slide  valve  engine  showing  the  point  of  cut-off     .     .     .     .321 

View    showing   the    position    of   the    valve    when    compression 
begins      ................    .     .     .     321,  322 

CHAPTER  XIII. 

TAKING  CHARGE  OF  A  STEAM  POWER  PLANT    .....  323 

Economy  in  steam  power  plants    ...     ........    327,  32 

Priming  in  boilers    .     .     .     .     ..............  3! 

Table  of  properties  of  saturated  steam   ...........  31 

High  pressure  steam    ...............    ;  132,  33 

Using  steam  full  stroke    ..............    335,337 


Xll  CONTENTS. 

PAGE. 

Slide  valve  engines . 337 

Regular  expansion  engines 338 

Automatic  cut-off  engines 339,340 

The  Gardner  spring  governor 341,  344 

The  Gardner   standard  governor 342,  344 

CHAPTER  XIV. 

A  FEW  REMARKS  ON  THE  INDICATOR 345 

The  use  of  the  indicator  in  setting  valves,  etc 346 

A  card  from  a  throttling  engine 347,  349 

A  card  from  an  automatic  cut-off  engine 350 

Calculating  mean  effective  pressure 351 

The  theoretical  curve 353,  357 

A  card  from  a  Corliss  engine 357 

A  stroke  card 358 

A  steam  chest  card 359 

Eccentric  out  of  place,  cards 360,361 

Eccentric  cards 361,365 

How  to  take  an  indicator  diagram 365 

Cards  from "  Eclipse "  ice  machine    ..    .     .     .     .     .     .     .     .     .     371,373 

A  collection  of  diagrams,  which  illustrate  very  nicely  the  peculiari- 
ties and  difference  in  the  action  of  throttling  and  automatic  en- 
gines . 375,  379 

CHAPTER  XV. 

ECONOMY  AND  OPERATION  OF  STEAM  ENGINES     ....  380 
The  question  whether  or  not  more  steam  is  used  when  an  engine  is 
made  to  run  faster  without  changing  either  the  cut-off  or  the  pres- 
sure     380 

How  to  increase  the  power  of  a  Corliss  engine  .     .     .     .     .     .     381,  382 

How  to  increase  the  power  of  an  engine  having  a  throttling  governor  383 
How  to  increase  the  horse  power  of  an  engine  having  a  shaft  gov- 
ernor      385 

How  to  line  an  engine  with  a  shaft  placed  at  a  higher  or  a  lower 

level    .     . 385,  387 

How  to  line  the  engine  with  a  shaft  to  which  it  is  to  be  coupled 
clireel},  .,,....,...<,,,...•...  387 


CONTENTS. 


PAGE. 
How  to  set  a  slide  valve  in  a  hurry  .........  3g8 

A  few  things  for  an  engineer  to  remember      .... 

The  travel  of  a  slide  valve    ............  u  39Q 

Loss  of  heat  from  uncovered  steam  pipes  ......  .391 

Rules  and  problems  appertaining  to  the  steam  engine     .     .     .     392,  395 
To  find  the  water  consumption  of  a  steam  engine    .....    395  397 

Table  of  sizes  of  boiler  feed  pump     ............   397 


CHAPTER  XVI. 

THE  STEAM  BOILER 398 

The  force  of  steam  and  where  it  comes  from      ......     398,  400 

The  energy  stored  in  steam  boilers 400,  401 

Special  high  pressure  boilers 401 

Types  of  boilers 402 

Horse  power  of  boilers         •     .     .     . 402, 404 

The  rating  of  boilers 404 

Working  capacity  of  boilers 405,  406 

Code  of  rules  for  making  boiler  tests 407,414 

Definitions  as  applied  to  boilers  and  boiler  material 415 

Heat  and  steam •     .     . 416,421 

Selection  of  a  boiler   ....... 422,  425 

Boiler  trimmings 426, 432 

The  care  and  management  of  a  boiler 433,  437 

Water  for  use  in  boilers 438,448 


CHAPTER  XVII. 

USE  AND  ABUSE  OF  THE  STEAM  BOILER     .     .     .     .     .    449,  453 

Design  of  steam  boilers    . *54>  455 

Forms  of  steam  boilers .  '  .     .     .    •  456 

Setting  steam  boilers 456>  457 

Defects  in  the  construction  of  steam  boilers .    457,453 

Improvements  in  steam  boilers •    *59>  4< 

Strength  of  riveted  seams 4(ilJ  *( 

Maximum  pitches  for  riveted  lap  joints      .     .     .     .     • *' 

Iron  plates  and  iron  rivets,  double  riveted  lap  joints 467 


XIV  CONTENTS. 

PAGE. 

Zigzag  riveting  and  chain  riveting 468,  472 

Single  riveted  lap  joints,  iron  plates 469 

Steel  plates  and  steel  rivets,  S.  R.  L.  J 470 

Steel  plates  and  steel  rivets,  D.  R.  L.  J 471 

Strength  of  stayed  flat  boiler  surfaces »  473 

Boiler  stays 474,  477 

Chart  to  find  steam  pipe  for  heating  water 478 

Chart  to  find  boiler  power  to  heat  water 479-483 

Data  relating  to  ventilation 484 

Sizes  of  mains  and  branches, —  table  of  pipe 485 

Pulsation  in  steam  boilers 487,  488 

Weight  of  square  and  round  iron  per  lineal  foot 488 

Water  columns  for  boilers 489 

Steam  gauges 489,  490 

Safety  valves 491,499 

Table  of  the  rise  of  safety  valves 494 

Safety  valve  rules 497 

Table  of  heating  surfaces  in  square  feet 501 

Centrifugal  force      . 501 


CHAPTER  XVIII. 

THE  WATER  TUBE  SECTIONAL  BOILER 502 

The  down  draft  furnace 503,  522 

View  of  boiler  setting  and  furnace  common  in  the  East 513 

Vertical  tubular  boilers 514,  521 

Proper  water  column  connections 515 

Table  of  pressures  allowable  in  boilers 516 

Fire  line  in  boiler  settings 520 

Proper  location  of  gauge  cocks 521 

Number  of  bricks  required  for  boiler  setting  .     .     .     • 522 

Specifications  for  a  sixty-inch  6-inch  flue  boiler 524 

Banking  flres 531 

Instructions  for  boiler  attendants 532 

Rules  and  problems  anent  steam  boilers      . 536 

Steam  jets  for  smoke  prevention 542 


CONTENTS.  xv 

CHAPTER  XIX. 

PAGE. 

THE  STEAM  PUMP ^ 

The  Worthmgton  compound  pump 544 

View  of  steam  valves  properly  set t  545 

The  Deane  steam  pump (  ^  5^6 

View  of  steam  valves  properly  set (  .  547 

The  Cameron  steam  pump    , (       543 

Explanation  of  steam  end 543 

View  of  steam  valves  properly  set     . 543 

The  Knowles  steam  pump ...... 550 

Explanation  of  steam  valves 550 

View  of  steam  valves  properly  set 552 

The  Hooker  steam  pump 553 

Operation  of  the  Hooker  pump 553 

View  of  steam  valves  properly  set 555 

The  Blake  steam  pump 555 

Operation  of  the  Blake  pump 556 

View  of  steam  valves  properly  set 558 

Miscellaneous  pump  questions  and  answers 559  and  571 

How  to  set  the  steam  valves  of  a  duplex  pump 567 

View  of  steam  valves  properly  set 568 

Proper  pipe  connections 569 

View  of  pipe  connections 570 

Pumps  refusing  to  lift  water 577 

Corrosion  in  water  pipes 579 

Pumping  acids 579 

Selecting  boiler  for  a  steam  pump 580 

The  Worthington  water  meter -    .581 

Table  of  water  pressure  due  to  height 582 

Table  of  decimal  equivalents  of  IGths,  32nds  and  64ths  of  an  inch     .  583 

Capacity  of  tanks  in  U.  S.  gallons 584 

Capacity  of  square  cisterns  in  U.  S.  gallons .    .  585 

Weight  of  water 685 

Cost  of  water 587 

Loss  by  friction  of  water  in  pipes a 

How  water  may  be  wasted ** 

Ignition  points  of  various  substances 68S 


XVI  CONTENTS. 

CHAPTER    XX. 

PAGE. 

THE  INJECTOR  AND  INSPIRATOR 591 

First  appearance  of  the  injector 592 

Range  of  the  inspirator  and  injector 592 

General  directions  for  piping  injectors 594 

Care  and  management  of  injectors 599,602 

Directions  for  connecting  and  operating  the  Hancock  inspirator   .     .  597 

Water  between  32°  and  212°  Fah 602 

Steam  pump  problems 603 

Water  pipe  problems 608 

CHAPTER  XXI. 

MECHANICAL  REFRIGERATION       619 

How  it  is  produced 619 

Principles  of  operation 620 

Operation  of  apparatus 620 

Function  of  the  pump  and  condenser 62 1 

What  does  the  work 621 

Mechanical  cold  easily  regulated 622 

Utilizing  the  cold 622 

Brine  system 622 

Direct  expansion  system 623 

Rating  of  the  machine  in  tons  capacity 623 

Difference  in  the  ratings 623 

Instructions  for  operating  refrigerating  machinery 624 

Steam  condensers 627 

Air  in  the  system « 628 

Gases  in  the  plant 628 

A  few  tests  for  ammonia 631 

Testing  for  water  by  evaporation 631 

Lubrication  of  refrigerating  machinery  . 632 

Effects  of  ammonia  on  pipes .  633 

To  charge  the  system  with  ammonia 634 

Process  of  mechanical  refrigeration 635 

View  of  the  "  Eclipse  "  compressor 637 

How  heat  is  removed 636 

Section  of  De  La  Vergne  compressors 638,  639 

Diagram  of  De  La  Vergne  system 640 


CONTENTS.  xv  jj 

PAGE. 

General  arrangement  of  refrigerating  plant  .    .     „  • 641 

De  La  Vergne  ice-making  plant      .     .     . .642 

Ice-making  plant,  showing  distilling  apparatus    ......    643 

Electrically-driven  ammonia  compressor 645 

Horizontal-vertical  refrigerating  machine „    646 

Location  of  high  and  low  pressure  gauges    .     , 647 

CHAPTER  XXII. 

SOME  PRACTICAL  QUESTIONS  USUALLY  ASKED  ENGI- 
NEERS WHEN  APPLYING  FOR  LICENSE  .  '. 

Reasons  why  pumps  do  not  work       

Priming  in  boilers 648 

Foaming  in  boilers 648 

In  case  of  low  water  in  a  boiler 649 

Best  economy  in  running  an  engine    . 650 

What  is  valve  lead        653,666,668 

What  is  meant  by  expansion  of  steam 654 

Describe  the  Corliss  valve  gear 654 

What  is  lap  on  a  valve      .     .     . .  654,666,670* 

Taking  up  lost  motion  in  an  engine .  654 

Direct  and  indirect  valve  motion 668- 

To  test  a  piston  for  leakage  of  steam      . 669 

CHAPTER  XXIII. 

INSTRUCTIONS  FOR  LINING  UP  EXTENSION  TO  LINE  SHAFT  672 

Simplicity  in  steam  piping 674 

Cutting  pipe  to  order 675 

Feed  water  required  for  small  engines 676 

Heating  feed  water 676 

Bating  boilers  by  feed  water     . *    ....  676 

Weights  of  feed  wa^er  and  of  steam 677 

Feed  water  heaters 678 

Table  showing  the  units  of  heat  required  to  convert  one  pound  of 
water  at  the  temperature  of  32°  Fah.,  into  steam  at  different  pres- 
sures  679 

Table  showing  gain  in  use  of  feed  water  heaters,  and  percentage  of 
heat  required  to  heat  water  for  different  feed  and  boiling  tempera- 
tures, as  compared  with  a  feed  and  boiling  temperature  of  212°  .  680 


XV1H  CONTENTS. 

- 

PAGE. 

Pure  water 681 

The  temperature  and  pressure  of  saturated  steam 684 

Something  for  nothing •     .  686 

Melting  point  of  metals 687 

Chimneys 688  to  694 

Weight  of  steel  smoke  stacks  per  linear  foot 694 

CHAPTER  XXIV. 

HORSE  POWER  OF  GEARS 695 

Table  of  H.  P.  of  shafts 697 

Prime  movers 697 

Wheel  gearing 698 

The  pitch  line  of  a  gear  wheel 698 

To  find  the  pitch  of  a  wheel      . 698 

To  find  the  chordal  pitch 699  to  703 

To  find  the  diameter  of  a  wheel 699  to  703 

To  find  the  number  of  teeth  for  a  wheel 699  to  703 

To  find  the  proportional  radius  of  a  wheel  or  pinion 700 

To  find  the  diameter  of  a  pinion        700 

To  find  the  circumference  of  a  wheel 700 

To  find  the  number  of  revolutions  of  a  wheel  or  pinion   ^     .     700  to  701 

Stress  on  gear  teeth 705 

A  train  of  wheels  and  pinions 701 

Table  of  diameters  and  pitches  of  wheels 704 

Curves  of  teeth   . 705 

Construction  of  gearing 706 

Bevel  wheels 707 

Worm-screw 708 

Proportions  of  teeth  of  wheels 709 

To  find  the  depth  of  a  cast-iron  tooth 709 

To  find  the  horse-power  of  a  tooth 710 

Calculating  the  speed  of  gears 710 

When  time  must  be  regarded 711 

Table  of  weight  of  a  square  foot  of  sheet  iron 712 

Screw  cutting 713 

Transmission  of  power  by  manila  rope 714,  812,  813 

Decimal  equivalents  of  one  foot  by  inches 714 

Table  of  transmission  of  power  by  wire  ropes 715  and  8 14 


CONTENTS.  x-lx 

CHAPTER  XXV. 


ELECTRIC  ELEVATORS 
The  Otis  elevator      ... 


........ 

Belt  driven  elevators    .  '     'TIC 

•      •      •      •       «      «      1  lo«  7*5 

Direct  connected  elevators    ..........  717  730 

The  motor-starting  switch    .........  '  71g 

The  elevator  machine  brake       .......  '  72n 

The  main  hand  rope      .........     .     .     ,  '  721 

View  of  connections  of  gravity  motor  controller  to  elevator  .'  722 

View  of  connections  of  gravity  motor  controller  with  separate  rope 
attachment  ...............  ^  72g 

Direct  connected  electric  elevators     ........  t  730 

Automatic  stops       .............  9  733 

View  of  circuit  connections      ..........     ,  <  734 

The  starting  resistance     ......         .........  735 

The  switch  lever      ..................  736 

Cutting  out  the  series  field  coils     ..."    ..........  737 

The  safety  brake  magnet  ................  739 

The  proper  care  of  machines     ............    739;  779 

How  to  start  the  car     .     ................  743 

The  car  switch     ...................  748 

The  slack  cable  switch      ................  749 

Electric  control  for  private  house  elevators     .........  749 

View  of  wiring  for  private  houses    .............  750 

The  Sprague  Electric  Co.'s  elevators      ...........  756 

View  of  operative  circuits  for  Sprague  screw  elevator    .....  762 

The  pilot  motor  .......  '  ............  763 

Care  of  electric  elevators     ...............  765 

Directions  for  the  care  and  operation  of  electric  elevators  ....  765 


CHAPTER  XXVI. 

ELECTRIC  ELEVATORS 769 

Drum  type,  limits  for  tall  buildings 769 

Motor  and  drum  speeds 769 

Diagram  of  Frazer  duplex  type 770 

General  arrangement  and  operation  of  duplex  type 771 

Duplex  elevator  motor  ,    • 772 


XX  CONTENTS. 

PAGE. 

Running  qualities  of  the  duplex  type  elevator    . 773 

Objections  to  the  duplex  elevat  >r 773 

Wiring  diagram  of  the  Frazer  duplex  elevator 774 

Controller  for  the  duplex  motor 775 

Frazer  limit  switch 776 

Detail  view  of  Frazer  controller 777 

The  traction  type  of  elevator      .     .     .     .     , ,  778 

Diagram  of  the  traction  type 779 

Considerations  concerning  traction-type  motors 780 

Cable-drive  elevator  machine 781 

Counter-balance  used  with  cable-drive  type ,     .  782 

Compl  te  installation  of  cable-drive  elevator ,  783 

Wiring  diagram  for  traction  elevator 784 

Controlling  device  for  electric  elevator 785 

Line  wires  for  traction  type 787 

Operation  of  car  and  limit  switches 787 

CHAPTER  XXVII. 

THE  DRIVING  POWER  OF  BELTS 788 

The  average  strain  or  tension  at  which  belting  should  be  run     .     .     .  788 

Rules  and  problems  anent  belting 788,  797 

Notes  on  belts 790 

Transmitting  power  of  belts 795 

Table  of  horse-power  of  belts 796,799 

Directions  for  adjusting  belting 798 

Horse  power  of  belting 799 

CHAPTER   XXVIII. 

AIR  COMPRESSORS,   THERMOMETERS,   THE   METRIC  SYS- 
TEM, AND  ROPE  TRANSMISSION 800 

Losses  in  air  compressors 800 

Capacity  of  air  compressors 800 

Contents  of  a  cylinder  in  cubic  feet  for  each  foot  in  length  ....  801 

The  McKierman  air  compressor 801 

The  Bennett  automatic  air  compressor 803 

The  Ingersoll-Sergeant  air  compressor 803 

The  Pohle  air  lift  system 807 


CONTENTS.  xx  j 

PAGE. 

The  metric  system 80) 

Thermometers t  gu 

Rope  transmission 812 

Horse-power  transmitted  by  hemp  ropes 813 

To  test  the  purity  of  hemp  ropes 814 

Wire  rope  data    .     0   • 814 

CHAPTER  XXIX. 

ALTERNATING  CURRENT  MACHINERY 815 

The  principles  of  alternating  currents 815 

Diagrams  representing  a  generator  of  either  continuous  or  alter- 
nating currents 817 

Diagrams  showing  the  relations  between  alternating  currents  and 

e.m.fs 821,824 

One  reason  why  alternating  currents  vary,  etc 825 

Diagrams  showing  the  way  in  which  sine  curves  are  used,  etc.     .    .  826 

Polyphase  currents       832 

Unbalanced  three-phase  currents,  etc 834 

Inductive  action  in  alternating  current  circuits,  etc 834 

The  angle  of  lag  between  the  current,  etc 837 

By  the  use  of  condensers,  etc 8*° 

The  general  principle  of  construction  of  a  condenser,  etc 841 

Mutual  induction 84:2 

Transformers       8' 

The  action  in  a  transformer 8 

The  object  in  using  transformers 8 

Alternating  current  generators 8 

Diagram  illustrating  a  simple  alternating  current  generator      ...  853 

Alternator  of  the  multipolar  type 8 

How  alternating  current  generators  are  run    ....•••••  8 

If  an  alternator  is  of  the  multipolar  type 854 

A  revolving  field  alternator       857 

An  inductor  alternator 

Alternating  current  generators 

Alternators  run  in  parallel 

Starting  alternators  connected  in  parallel 

The  way  in  which  synchronizing  lamps  are  connected      .     . 
Compensating  and  compounding  alternators 


XX11  CONTENTS. 

PAGE. 

Field  magnetizing  currents a    ..  867 

Alternating  current  motors .     .  867 

Two-phase  revolving  field  synchronous  motor «     .  869 

Power  factor • 870 

Induction  and  other  types  of  motors 871 

Principle  of  the  induction  motor • 872 

Induction  motors  if  very  small 877 

Three-phase  induction  motors 877 

While  induction  motors  are  very  satisfactory  machines 878 

Rotary  transformers  and  rotary  converters      .     .     .......  878 

Principle  of  the  rotary  transformer 879 

Alternating  current  distributions 882 

Starting 886 

Parallel  running  of  alternators      . 887 

Types  suitable  for  parallel  operation      .     .     .     .     • 887 

Division  of  load       887 

Compound  alternators 887 

Belted  machines 888 

Direct  coupled  machines 888 

Starting 889 

Shutting  down 890 

Care  of  machines 890 


CHAPTER  XXXo 

TABLES  — 

Actual  ratios  of  expansion 935 

Ammonia  gas  per  ton  refrigeration „     .  898 

Boiling  points  of  various  substances „     .     .     .     .     .  907 

Capacity  of  duplex  pumps 893 

Capacity  of  low  pressure  pumps    . 984 

Capacity  of  reservoir  in  gallons 910 

Coal  burned  per  square  foot  of  grate 908 

Cost  of  coal  per  annum 909 

Diameters,  circumferences  and  areas  of  circles ,     .    .  895 

Horsepower  for  one  pound  m.e.p 924 

Horsepower  of  slide-valve  engines 922 


CONTENTS.  xxjj; 

PAGE. 

Horsepower  per  ton  of  refrigeration 904 

Horsepower  to  compress  one  cu.  ft.  ammonia     .     . 

Hyberbolic  logarithms '  gg2 

Iron  and  steel  hoisting  ropes '  91g 

Iron  and  steel  transmission  ropes 918 

Mean  absolute  pressures 925 

Mean  pressure  of  diagram,  ammonia  compressor    .  .  902 

Measurements  of  riveted  seams 929-934 

Melting  points  of  fusible  plugs .  t  907 

Melting  points  of  various  substances t  997 

Piston  speed  in  feet  per  minute .  912 

Power  gained  by  adding  condenser 923 

Properties  of  ammonia 597 

Properties  of  brine  solution       900 

Properties  of  carbonic  acid 900 

Properties  of  saturated  steam 330,  913 

Properties  of  sulphur  dioxide 898 

Reaumur,  Fah.  and  Celsius  thermometers       903 

Ropes  for  inclined  planes 920 

Speed  and  capacity  of  centrifugal  pumps 927 

Sizes  and  dimensions  of  Corliss  engines 926 

Sizes  of  cylinders  for  compound  pumps 923,  927 

Specifications  for  riveted  seams 928 

Transmission  of  power  by  ropes 921 

Weight  and  strength  of  iron  bolts 906 

Weight  of  rivets  and  bolts 905 

Horizontal  return  tubular  boilers 937,  938-939 

Table  of  wages e    .    924 

Air  for  Rock  drills 934 

Areas  of  segments  of  circles .    .    .    o     .    935 

Staying  boiler  heads 938 

Table  of  Steam  Pressure  per  square  inch  allowable  on  lap 

welded  flues  made  in  sections '  •    •    952,  953 

Steam  Pressure  allowable  on  lap-welded  flues 952,  953 


CHAPTER  XXXI, 

HYDRAULIC  ELEVATORS 964 

Types  of  elevator  machines 954 

Horizontal  pushing  type 955,  957 

Actuating  lever  in  the  car   a    a    -    •    - •         ••    .956 


XXIV  CONTENTS. 

PAGE. 

Elevation  of  horizontal  machine 958 

Plan  of  elevator  cylinder  and  sheaves 960 

Pilot  and  main  valves 961 

Morse  and  Williams  horizontal  pushing  type 962 

Horizontal  elevators,  pulling  type 963 

Whittier  pulling  type 964 

Valve  of  Whittier  machine 965 

Automatic  stop  for  Whittier  machine 967 

Otis  vertical  elevator 968 

Otis  vertical  elevator  system 969 

The  Otis  valve 970 

Valve  construction 971 

Otis  machine  with  pilot  valve  control 972 

Method  of  operating  Otis  pilot  valve 973 

Main  valve  with  pilot  valve  control 974 

Details  of  Otis  pilot  valves 975 

Otis  differential  and  pilot  valve 977 

Main  valve  with  magnet-operated  pilot      .     » 978 

Pipe  connections  for  magnet-operated  pilot 979 

Otis  main  valve  with  magnet  control 981 

Pipe  connections  for  Otis  main  valve 982 

Private  house  elevator,  push-button  control 984 

Floor  controller  for  push-button  system 985 

Wiring  diagram  for  push-button  system 987 

Double  power  hydraulic  elevators 987 

High  pressure  hydraulic  elevators 988 

Otis  double  pressure  type 989 

High  pressure  horizontal  machine , 991 

Hydraulic  elevator  system  with  inverted  plunger 993 

Valves  used  with  inverted  plunger  type .     •     .     .     .  995 

Automatic  stop  valve  for  plunger  type 996 

Speed  controller  for  plunger  type    .     .     s     ,     ,...*>..  998 

Plunger  elevators ».-...  998 

Accumulators  used  with  plunger  type  .....»•••*.  999 

Valve  for  accumulator 1000 

Plunger  elevator,  complete  installation s     .  1002 

Plunger  Elevator  Co'.s  machine 1004 

Details  of  plunger  elevators 1006 


CONTENTS.  xxy 


PAGB. 

Pilot  and  automatic  stopping  valves 1007 

Valve  for  elevator  control 

Elevator  for  pilot  valve  control  ............. 

How  to  pack  vertical  cylinder  machine      . t  10i2 

Plunger  elevator  with  hand  rope  control 1013 

Valve  for  hand  rope  control .1014 

Packing  vertical  cylinder  piston  from  top 1015 

Packing  vertical  cylinder  valves       .1016 

Packing  piston  rods 1016 

Water  for  use  in  hydraulic  elevators 1017,  1022 

Causes  for  car  settling .     .  1019 

Elevator  enclosures  and  their  care 1019 

Standard  hoisting  rope , 1021 

Cables  and  how  to  care  for  them 1021 

Leather  cup  packings  for  valves 1022 

Closing  down  elevators , 1022 

Lubrication  for  hydraulic  elevators • 1023 

Useful  information 1023 

Decimal  equivalents  of  an  inch 1021 

Water , 1024 

Elevator  safeties 1025 

Otis  wedge  safety 1026 

Safety  governor,  single  acting 1028 

Otis  roller  safety 1029 

Governor  rope  for  roller  safety 1030 

Lifting  rope  for  roller  safety 1031 

Brake  safety  for  iron  guides « 1032 

Governor  rope  for  brake  safety 

Morse  and  Williams,  brake  safety 1°35 

Pratt  brake  safety 1036 

Otis  double  acting  safety  governor .     .  li 

Pipes  and  Tanks.     Contents  in  cubic  feet;  in  U.  S.  gallons    .     .     .1039 

Friction  and  lubrication 1( 

Uses  of  friction 1( 

Coefficient  of  friction 1( 

Illustrating  laws  of  friction 1( 

1044 
Laws  of  friction 

Theory  of  lubrication *' 

Petroleum  oils - 


XXVI  CONTENTS. 

PAGE 
The  conditions  which  produce  the  greatest  difference  in 

ordinary  lubrication 104 

The  best  lubricant 104 

Cylinder  and  valve  lubrication 104! 

Wet  steam 105' 

Lubrication  of  refrigerating  machinery 105 

Different  makes  of  refrigerating  machines 1054 


HANDBOOK   ON   ENGINEERING. 


CHAPTER     I. 

THE    ELEMENTARY    PRINCIPLES    OF    ELECTRICAL 
MACHINERY. 

The  operation  of  electric  generators,  or  dynamos,  as  they  are 
ordinarily  called,  and  also  that  of  electric  motors,  depends  upon 
a  simple  relation  between  electricity  and  magnetism,  which  will 
be  explained  in  a  simple  manner  in  the  following  paragraphs. 


s 


[JT 


Fig.  4. 


Fig.  1.  Fig.  2.  Fig.  3. 

Forms  of  magnets. 

A  permanent  magnet,  as  is  well  known,  is  a  bar  of  steel  which 
possesses  the  power  of  attracting  pieces  of  iron.  These  bars  may 
be  made  straight,  as  in  Fig.  1,  or  in  the  form  of  a  U,  as  in  Fig. 
2,  or  in  any  other  shape  desired.  The  strength  of  a  permanent 
magnet  depends  upon  the  kind  of  steel  of  which  it  is  made,  and 

1 


2  HANDBOOK    ON    ENGINEERING. 

also  upon  the  temper  it  is  given.  Generally  speaking,  the  harder 
the  steel  the  stronger  the  magnet.  A  bar  of  soft  steel,  or  wrought 
iron,  cannot  be  made  into  a  permanent  magnet  of  any  noticeable 
strength,  but  if  such  a  bar  is  covered  with  a  coil  of  wire,  as  shown 
in  Figs.  3  and  4,  and  a  current  of  electricity  is  passed  through 
the  wire,  the  bar  will  be  converted  into  a  very  strong  magnet  so 
long  as  the  current  flows.  As  soon  as  the  electric  current  stops 
flowing  through  the  wire,  the  magnetism  of  the  bar  will  die  out. 
Magnets  of  the  last-named  type  are  called  electro-magnets,  as 
they  do  not  possess  magnet  properties  except  when  the  electric 
current  flows  around  them.  Electro-magnets,  when  energized  by 
sufficiently  strong  electric  currents,  can  be  far  more  powerful  than 
the  permanent  magnets,  and  on  that  account  they  are  used  in 
electric  generators  and  motors.  In  addition  to  being  a  stronger 
magnet,  the  electro-magnet  has  the  advantage  that  it  can  be 
magnetized  and  demagnetized  almost  instantly,  by  simply  cutting 
off  the  exciting  electric  current,  and  on  this  account  they  can  be 
used  for  parts  of  electrical  machines  and  apparatus,  for  which  the 
permanent  magnet  would  be  entirely  unsuited. 

If  we  test  the  attractive  power  of  a  magnet,  we  will  find  that 
it  is  greatest  at  the  ends,  the  force  at  the  middle  point  being 
scarcely  noticeable.  A  bar  such  as  Fig.  1  or  Fig.  3  might  hold  a 
piece  of  iron  weighing  several  pounds ,  if  presented  to  either  end , 
while  at  the  middle  point,  it  might  not  be  able  to  sustain  more 
than  an  ounce  or  two.  Owing  to  this  fact,  the  ends  are  called 
the  poles  of  the  magnet. 
When  a  magnet  is  suspended  from  its  center,  like  a  scale  beam, 
and  allowed  to  swing  freely,  it  will  be  found  that  it  will  come  to 
rest  in  a  north  and  south  position,  and  no  matter  how  violently  it 
may  be  moved  around,  it  will  always  come  to  a  state  of  rest 
with  the  same  end  pointing  towards  the  north.  On  this  ac- 
count, the  ends  are  called  north  and  south  poles,  the  north  pole 
being  the  end  that  points  toward  the  north. 


HANDBOOK    ON    ENGINEERING.  3 

If  two  bar  magnets  are  suspended  side  by  side  with  the 
north  end  of  one  at  the  top  and  the  north  end  of  the  other 
at  the  bottom,  as  illustrated  in  Fig.  5,  they  will  attract  each 
other;  but  if  both  magnets  have  the  north  end  at  the  top,  they 
will  push  away,  as  shown  in  Fig.  6.  It  is  evident  that  there  is 
a  good  reason  for  this  difference  in  action,  and  this  reason  we 
can  obtain  by  experiment. 


a 


a 


Figs.  5  and  6.    Showing  effect  of  changing  the  poles. 

A  magnet  needle,  such  as  is  used  in  the  mariner's  compass,  is 
simply  a  small  magnet.  If  we  place  a  magnet  bar,  as  shown  in 
Fig.  7,  and  then  set  near  to  it,  in  different  positions,  a  compass 
containing  a  very  small  needle,  we  will  find  that  in  these  several 
positions  the  direction  of  the  needle  will  be  about  as  is  indicated 
by  the  small  arrows  marked  b  on  the  curved  lines  a  a;  the  arrow 
pointing  towards  the  north  end,  or  pole  of  the  needle.  The 
reason  why  the  needle  will  take  up  these  positions  is  that  the  north 
end  of  the  bar  attracts  the  south  end  of  the  needle,  and  pushes 
away  the  north  end,  just  as  in  Figs.  5  and  6,  and  the  south  end 
of  the  bar  acts  in  the  same  way ;  so  that  there  is  a  tug  of  war 
going  on,  so  to  speak,  between  the  attractions  and  repulsions  of 


4  HANDBOOK    ON    ENGINEERING. 

the  two  ends  of  the  bar  upon  the  two  ends  of  the  needle,  the 
result  being  that  the  position  assumed  by  the  needle  is  the  re- 
sultant of  these  several  forces.  When  the  needle  is  near  the 


\ 


V 


Of 

y 


^pp^'' 


.    Figs.  7  and  8.    Illustrating  lines  of  force. 

north  pole  of  the  bar,  its  south  end  is  attracted  with  the  greatest 
force,  and  when  near  the  south  end  of  the  bar,  the  north  end  ex- 
periences the  greatest  attraction. 

If  we  were  to  place  the  exploring  needle  in  all  possible  posi- 
tions near  the  magnet  and  trace  lines  parallel  with  it,  in  these 
positions,  we  would  obtain  a  large  number  of  curves  about  the 
shape  of  those  shown  in  Fig'.  8.  As  these  curves  represent  the 
direction  into  which  the  magnet  needle  is  turned  at  the  various 
points  in  the  vicinity  of  the  magnet,  they  represent  the  direction 
in  which  the  combined  forces  of  the  two  poles  act  at  these  two 
points,  hence,  these  lines  are  called  magnetic  lines  of  force. 


HANDBOOK    ON    ENGINEERING. 


When  two  magnets  are  suspended  as  in  Fig.  5,  the  lines  of 
force  of  both  will  be  in  the  same  direction  as  is  indicated  in  Fig. 
9  by  the  arrow  heads  on  the  curves  a  a.  That  this  is  true  can  be 
seen  from  Fig.  7,  in  which  it  will  be  seen  that  the  arrow  heads 
point  toward  the  south  pole  and  away  from  the  north  pole. 
As  the  north  pole  of  a  magnet  has  an  attraction  for  the  south 
pole,  we  can  readily  see  that  there  is  an  endwise  pull  in  the 
lines  of  force,  which  tends  to  make  them  contract,  like  rubber 
bands,  hence,  we  can  imagine  the  lines  a  a  in  Fig.  9  to  contract 
and  thus  draw  the  two  magnet  bars  together. 

The  repulsion  of  the  two  magnets,  when  the  north  poles  are  at 
the  same  end,  is  illustrated  in  Fig.  10.  Here  we  see  that  the  lines 
of  force  passing  on  the  outside  of  the  bars,  as  indicated  by 
lines  a  a,  are  unobstructed,  and  can  assume  their  natural  posi- 


a 


s 


JV 


Figs.  9  and  10.    Lines  of  force  in  two  bar  magnets. 

tion,  but  those  that   pass  between  the  bars,  along  line   c,   are 
pressed  out  of   position.     If  we   assume  that  the  lines  of 
make   an    effort   to   retain  their    position,    like   so   many  wir< 


6  HANDBOOK    ON    ENGINEERING. 

springs,  then  we  can  see  that  the  repulsion  is  due  to  the  effort  that 
the  lines  make  to  assume  their  natural  form  in  the  space  between 
the  bars. 

Magnetic  lines  of  force  have  no  real  existence,  they  simply  in- 
dicate the  direction  in  which  the  force  acts,  but  if  we  keep  this 
fact  in  mind,  it  helps  us  to  understand  magnetic  actions,  if  we 
treat  the  lines  of  force  as  if  they  were  something  real.  This  fact 
will  become  more  evident  as  we  proceed. 

Lines  of  force  always  pass  from  the  north  to  the  south  pole 
through  the  space  between  these  poles,  and  through  the  magnet 
itself,  they  are  assumed  to  pass  from  the  south  to  the  north  pole. 
The  form  of  the  lines  of  force  depends  upon  the  relative  position 
of  the  north  and  south  poles.  In  Fig.  9  they  are  curved,  as 

a 


<s 

JV 

55== 

S                              JV 

Fig.  11.    Lilies  of  force  between  ends  of  magnets. 

the  magnets  are  placed  side  by  side,  but  if  the  bars  were  arranged 
end  to  end,  as  in  Fig.  11,  the  lines  of  force  would  be  straight,  as 
is  shown  at  a.  From  the  north  end  of  the  right  side  magnet,  the 
lines  of  force  would  pass  in  curved  line,  as  in  Fig.  10,  to  the  south 
pole  of  the  magnet  on  the  left  side,  thus  completing  the  magnetic 
chain,  or  circuit,  as  it  is  called. 

If  we  take  the  two  magnet  bars  of  Fig.  1 1  and  stand  them  on 
end,  as  in  Fig.  12,  and  suspend  a  bent  wire  C  in  the  manner 
shown,  effects  can  be  produced  that  are  interesting  and  instruct- 
ive, as  they  illustrate  the  principle  upon  which  generators  and 
motors  act.  The  wire  C  should  be  journaled  at  D  D,  so  as  to 
swing  with  as  little  friction  as  possible,  and  its  ends  are  to  be  con- 
nected with  a  battery  J5,  by  means  of  fine  wires  a  and  b ;  a  switch 
being  provided  at  c  so  as  to  stop  the  flow  of  current  when  desired. 


HANDBOOK    ON    ENGINEERING.  7 

If  the  switch  c  is  opened,  so  that  no  current  flows  through  C,  the 
latter  will  not  be  disturbed,  and  if  we  give  it  a  swing,  it  will  oscil- 
late back  and  forth,  like  a  clock  pendulum,  and  in  a  few  seconds 
come  to  rest  in  the  position  in  which  it  is  shown.  If  the  switch 
is  closed,  C  will  at  once  swing  out  of  the  stream  of  magnetic  lines 
of  force  and  will  remain  in  that  position  as  long  as  the  current 
from  the  battery  passes  through  it.  The  direction  in  which  C 


Fig.  12.    Showing  the  principle  of  the  electric  generator 


will  swing  will  depend  upon  the  direction  of  the  current  through 
it.     If  with  the  wires  a  and  b  connected  with  the  battery,  in  the 
manner    shown,    the   wire  C  swings  to  the  right  side,  then  if  a  is 
connected   with    e,  and  b  with  d,  the  direction  of  swing  will 
reversed  ;  that  is,  C  will  swing  toward  the  left. 

From  this  experiment  we  see  that  the  magnetic  lines  of 
can  develop  a  repulsive  force  against  an  electric  current,  ai 
the  direction  of  the  repulsion  depends  upon  the  direct* 


8 


HANDBOOK    ON    ENGINEERING. 


electric  current  with  respect  to  the  direction  of  the  lines  of  force. 
We  shall  now  explain  why  this  repulsion  is  developed,  and  this 
we  can  illustrate  by  the  following  experiments:  — 

If  we  arrange  three  wires  as  shown  in  Figs.  13,  14  and  15,  so 
as  to  run  north  and  south,  the  upper  end  being  north,  and  place 
over  these  magnet  needles  D  D  D,  pivoted  at  e  e  e,  we  will  find 
that  if  there  is  no  current  flowing  through  the  wire,  the  needle 
will  point  toward  the  north,  or  be  parallel  with  the  wire,  as  is 


Fig.  13.  Fig.  14.  Fig.  15. 

Showing  effect  of  current  on  the  needle. 

shown  in  Fig.    14.     If  the  current  flows  through  the  wire  from 

south  to  north,  the  north  end  of  the  needle  will  swing  to  the  right, 
as  in  Fig.  15,  and  if  the  current  flows  through  the  wire  from  north 
to  south,  the  north  end  of  the  needle  will  swing  toward  the  left, 
as  in  Fig.  13.  From  this  we  see  that  an  electric  current  can 
repel  a  magnet,  and  that  the  direction  in  which  it  repels  it  depends 
upon  the  direction  of  the  current. 

If  we  stand  the  three  wires  on  end,  as  shown  in  Figs.  16,  17 
and  18,  in  which  A  B  C  represent  the  wires  as  seen  from  above, 
we  will  find  out  more  about  the  relation  between  electric  currents 


HANDBOOK    ON    ENGINEERING.  9 

and  magnets.  If  we  place  four  small  magnet  needles  around  each 
one  of  the  wires,  as  shown  at  a  a  a  a,  we  will  find  that  those 
around  the  center  wire,  through  which  no  current  flows,  will  all 

a 


Fig.  16.  Fig.  17.  Fig.  18. 

Wires  surrounded  by  magnetic  lines  of  force. 

point  toward  the  north,  as  shown,  while  those  around  the  wire 
Fig.  16,  through  which  a  current  flows  upward,  that  is,  away  from 
the  center  of  the  earth,  will  point  in  a  direction  opposite  to  that 
in  which  the  hands  of  a  clock  move;  and  in  wire  Fig.  18,  in 
which  the  electric  current  flows  down  toward  the  center  of  the 
earth,  the  north  ends  of  all  the  needles  will  point  in  the  direction 
in  which  the  hands  of  a  clock  move,  that  is,  just  opposite  to  those 
in  Fig.  16. 


Figs.  19  and  20.    Directions  of  lines  of  force. 
From  these  actions,  we  infer  at  once    that  when  an  electrio 
current  flows  through    a  wire,  the    latter    becomes    surrounded 
with  magnetic  lines  of  force,  as  is  illustrated  in  Figs.  19  and  20, 


10  HANDBOOK   ON    ENGINEERING. 

and  that  there  is  a  fixed  relation  between  the  direction  of  the 
current  and  that  of  the  lines  of  force.  At  A,  Fig.  19,  the  direc- 
tion of  the  lines  of  force  is  shown  for  a  current  moving  up- 
ward, and  at  J5,  Fig.  20,  the  direction  of  the  lines  of  force  is 
that  due  to  a  current  moving  downward  through  the  wire. 

Inasmuch  as  an  electric  current  flowing  through  a  wire  is 
surrounded  by  magnetic  lines  of  force,  we  can  say  that  a  com- 
plete electric  current  consists  of  two  parts,  one  the  current  proper, 
which  traverses  the  wire,  and  the  other  the  magnetic  casing  which 
envelops  the  wire.  It  is  the  action  between  the  latter  part  of  the 
current  and  the  lines  of  force  of  magnets  that  develops  the 
current  in  a  generator,  or  the  power  in  a  motor. 

With  the  aid  of  Figs.  21  and  22,  we  can  now  show  how  the 
force  is  developed  that  thrusts  the  wire  to  one  side  in  Fig.  12. 
The  lines  of  force  of  the  magnet,  which  constitute  what  is  called 
the  magnetic  field,  will  flow  from  the  north  pole  at  the  top  to  the 
south  pole  at  the  bottom,  as  is  shown  in  Figs.  21  and  22.  If  the 
electric  current  flows  through  the  wire  C  from  the  back  toward 
the  front,  the  lines  of  force  developed  around  it  will  have  the 
direction  shown  in  Fig.  21.  As  lines  of  force  cannot  flow  in  op- 
posite directions  in  the  same  space,  the  lines  of  the  field  will  swing 
over  to  the  left  side  of  the  wire,  but  in  doing  so  they  will  be 
stretched  out  of  the  straight  form,  and  they  will  also  push  the 
lines  surrounding  the  wire  out  of  their  central  position.  Under 
these  conditions,  which  are  illustrated  in  Fig.  21,  the  effort  made 
by  the  field  lines  to  straighten  out,  together  with  the  effort  made 
by  the  wire  lines  to  return  to  the  central  position,  will  develop  a 
thrust  between  the  wire  and  the  field,  and  thus  force  the  former 
out  toward  the  right  side. 

If  the  direction  of  the  current  through  the  wire  is  reversed  so 
as  to  flow  from  front  to  back,  the  direction  of  the  lines  of  force 
around  the  wire  will  be  reversed,  and  will  be  as  in  Fig.  22.  Under 
these  conditions,  the  lines  of  force  of  the  magnetic  field  will 


HANDBOOK    ON    ENGINEERING.  jj 

swing  over  to  the  right  side  of  the  wire,  and  thus  the  thrurt  will 
be  in  the  opposite  direction. 

Fig.  \2  represents  the  principle  of  an  electric  motor  in  ite  sim 
plest  form,  and  from  it  we  see  that  the  force  that  causes  the 
armature  to  rotate  is  developed  by  the  repulsion  between  the  mag- 
netism  of  the  field  magnet  and  the  magnetism  that  surrounds  the 
wires  wound  upon  the  armature. 


V 


Figs.  21  and  22.    Showing  effect  of  magnetic  Aeld. 

It  is  self-evident  that  if  we  undertake  to  force  the  wire  C 
through  the  magnetic  field  in  the  opposite  direction  to  that  in 
which  it  swings,  we  will  have  to  make  an  effort  to  do  so ;  that  is, 
if  we  try  to  move  the  wire  from  right  to  left  in  Fig.  21,  or  from 
left  to  right  in  Fig.  22,  we  will  have  to  apply  power.  Now  nature 
is  a  strict  accountant  and  does  not  allow  any  power  to  be  lost ; 
therefore,  all  the  energy  we  expend  in  moving  the  wire  through 
the  magnetic  field  must  appear  in  some  other  form,  and  the  form 
in  which  it  appears  is  as  an  electric  current  that  is  generated  in 


12  HANDBOOK    ON    ENGINEERING. 

the  wire.  If  we  were  to  remove  the  battery  in  Fig.  12  and  put 
in  its  place  an  instrument  to  indicate  the  presence  of  a  current  in 
the  wire,  we  would  find  that  ,>hen  we  move  the  latter  in  the 
opposite  direction  to  that  in  which  it  moves  under  the  influence  of 
the  current,  we  generate  a  current;  that  is,  we  convert  the  device 
into  a  simple  electric  generator.  If  in  Fig.  21,  we  move  the  wire 
from  right  to  left,  the  direction  of  the  current  generated  in  the 
wire  will  be  the  same  as  that  of  the  current  which  causes  the  wire 
to  swing  in  the  opposite  direction,  that  is,  from  back  toward  the 
front.  As  it  is  a  poor  rule  that  does  not  work  both  ways,  we 
would  naturally  infer  that  if  moving  the  wire  from  right  to  left 
develops  a  current  from  back  to  front,  movement  in  the  opposite 
direction  would  develop  a  current  from  front  to  back ;  and  such 
is  actually  the  case.  This  fact  can  be  demonstrated  by  Fig.  12. 
Suppose  that  in  this  figure  we  hold  C  stationary  in  the  central 
position,  and  then  pass  a  current  through  from  back  toward  the 
front ;  this  current  would  exert  a  force  to  swing  C  to  the  right 
side.  If  we  release  the  wire,  it  will  swing  to  the  right  and  as 
soon  as  it  begins  to  move,  the  current  will  become  weaker,  show- 
ing that  the  movement  of  the  wire  developed  therein  a  current  in 
the  opposite  direction.  If  we  force  the  wire  over  to  the  left  side, 
the  current  flowing  through  it  will  begin  to  increase  as  soon  as 
the  wire  moves. 

All  the  foregoing  shows  us  that  when  a  wire  is  moved  through 
a  magnetic  field,  a  current  will  be  generated  in  it  if  it  forms  part 
of  a  closed  circuit,  and  it  makes  no  difference  whether  there  is  a 
current  already  flowing  in  the  wire  or  not.  When  the  wire  is 
caused  to  move  through  the  magnetic  field  by  a  current  flowing 
through  it  from  an  external  source,  the  current  developed  in  it  will 
be  in  opposition  to  that  which  comes  from  the  external  source, 
and,  as  a  consequence,  the  movement  produces  an  actual  reduc- 
tion of  the  strength  of  current  flowing  through  the  wire.  The 
stronger  the  magnetic  field  and  the  greater  the  velocity  of  the 


HANDBOOK   ON   ENGINEERING.  13 

wire,  the  stronger  the  current  generated  in  opposition  to  the  driv- 
ing current,  and,  therefore,  the  weaker  the  latter.  It  is  on  this 
account  that  if  a  motor  is  allowed  to  run  free,  the  faster  it  runs 
the  weaker  the  current  through  it  becomes,  as  the  actual  current 
in  every  case  can  only  be  the  difference  between  the  main  driving 
current  and  the  one  developed  in  the  wire,  which  latter  runs  in 
the  opposite  direction. 

Magnetic  force  is  measured  in  units  that  are  based  upon  the 
centimeter  gram  second  system  which  is  too  technical  to  be  ex- 
plained in  a  few  words.  Briefly  stated  a  unit  of  magnetic  force 
will  exert  a  pull  of  unit  mechanical  force  at  a  unit  distance. 

The  force  of  magnets  is  measured  either  by  the  total  force  of 
the  magnet,  or  by  the  force  exerted  by  each  unit  of  cross-section. 
When  the  measurement  is  based  upon  the  total  force  of  the  mag- 
net, the  unit  is  called  a  Maxwell ;  thus  we  speak  of  the  total  flux 
of  a  magnet  as  so  many  maxwells.  When  the ,  measurement  is 
referred  to  the  force  per  unit  of  cross-section,  it  is  spoken  of  as 
the  magnetic  density,  or  density  of  magnetization,  and  the  unit 
used  is  called  a  Gauss ;  thus  we  speak  of  a  magnet  as  having  a 
density  of  so  many  gausses  per  square  centimeter,  or  square 
inch  of  cross-section.  The  density  of  magnetization  is  deter- 
mined by  a  rule  given  on  page  46. 

The  lifting  capacity  of  a  magnet  can  be  determined  by  the 
following  rule :  — 

TO    FIND    THE    LIFTING    CAPACITY    OF    A    MAGNET    IN   POUNDS. 

Multiply  the  area  of  cross-section  of  the  magnet  pole  in  square 
inches,  by  the  square  of  the  density  of  magnetization  per  square 
inch,  and  divide  this  product  by  72  millions. 

This  rule  gives  the  pull  for  one  pole.  For  horse  shoe  magnets 
double  the  figures.  If  the  object  lifted  is  not  in  contact  with 
the  poles  the  pull  will  be  less  than  rule  gives. 


14  HANDBOOK    ON    ENGINEERING 


CHAPTER     II. 
THE  PRINCIPLES  OF  ELECTROMAGNETIC  INDUCTION. 

By  electromagnetic  induction,  is  meant  the  induction  of  electric 
currents  by  magnetic  action.  In  the  preceding  chapter  it  has  been 
shown  that  if  we  move  a  wire  through  a  magnetic  field,  an  electric 
current  will  be  generated  in  it,  providing  its  ends  are  joined,  so 
as  to  form  a  closed  circuit.  If  the  ends  are  not  joined,  then  there 
will  be  no  current  developed,  because,  an  electric  current  cannot 
flow  except  in  a  closed  circuit.  When  the  ends  of  the  wire  are 
not  joined,  the  movement  through  the  field  develops  simply  an 
electromotive  force.  Electromotive  force  is  that  force  which 
causes  an  electric  current  to  flow  when  there  is  a  circuit  in  which 
it  can  flow.  Electromotive  force  is  a  long-winded  name  and  on 
that  account  it  is  always  abbreviated  into  e.m.f.,  so  that  here- 
after when  these  letters  are  used,  it  will  be  understood  that  they 
stand  for  electromotive  force. 

Metals  and  all  other  substances  that  allow  electric  currents 
to  flow  through  them  are  called  conductors,  while  glass,  mica, 
wood,  paper  and  many  other  similar  forms  of  matter  that  do  not 
allow  currents  to  flow  through  them  are  called  insulators.  The 
difference  between  conductors  and  insulators  is  only  one  of 
degree,  for  there  is  no  known  substance  that  is  an  absolute  non^ 
conductor  of  electricity  ;  that  is,  a  perfect  insulator  ;  and  there  is 
no  substance  that  does  not  resist  to  some  extent  the  passage  of  a 
current  —  that  is,  there  is  no  such  thing  as  a  perfect  conductor. 
Some  substances,  like  damp  paper  or  wood,  which  stand  midway 
between  good  conductors  and  good  insulators,  can  be  regarded  as 
Cither  one  or  the  other,  depending  upon  the  service  for  which  they 
are  used.  For  currents  of  very  low  e.m.f.,  they  would  be  in- 


HANDBOOK    ON    ENGINEERING.  15 

sulators,  but  for  currents  of  very  high  e.m.f.,  they  would  be 
conductors. 

The  current  that  will  flow  through  any  circuit  when  impelled 
by  an  e.m.f.,  will  have  a  strength  that  will  depend  upon  the 
amount  of  resistance  that  opposes  its  flow.  As  all  conducting 
materials  are  not  of  the  same  degree  of  conductivity,  their  relative 
values  are  determined  by  the  amount  of  resistance  they  interpose 
to  the  flow  of  the  current.  The  resistance  of  a  conductor  is 
measured  in  units  called  ohms;  the  strength  of  current  is 
measured  in  units  called  amperes,  and  the  e.m.f.  is  measured  in 
units  called  volts.  The  relation  between  these  units  is  such  that 
an  e.m.f .  of  one  volt  will  cause  a  current  of  one  ampere  to  flow 
in  a  circuit  having  a  resistance  of  one  ohm. 

When  a  wire  is  moved  through  a  magnetic  field,  the  e.m.f. 
induced  in  it  will  be  determined  by  the  strength  of  the  field  and 
the  velocity  with  which  the  wire  moves,  and  will  not  be  affected 
in  any  way  by  the  resistance  of  the  circuit  of  which  the  wire 
forms  a  part.  If  the  resistance  is  very  great,  the  strength  of 
current  generated  will  be  very  low,  and  if  the  resistance  is  very 
low  the  current  will  be  strong,  but  in  either  case  the  e.m.f.  will 
be  the  same. 

If  movement  of  the  wire  in  one  direction  develops  an  e.m.f. 
in  a  given  direction  through  the  circuit,  then  movement  of  the 
wire  in  opposite  direction  will  reverse  the  direction  of  the  e.m.f. 
Thus,  in  Fig.  23,  which  represents  a  magnetic  field  between 
the  poles  N  $,  if  wire  a  is  moved  'from  right  to  left,  it  will  have 
induced  in  it  an  e.m.f.  that  will  be  from  back  to  front,  and  if 
the  direction  of  motion  of  the  wire  is  reversed,  the  e.m.f.  will 
also  be  reversed.  This  will  be  true  whether  the  wire  is  near  the 
N  pole  or  S  pole.  This  being  the  case,  it  can  be  seen  that  if 
a  represents  the  end  of  a  wire  moving  in  the  direction  of  arrow 
d,  and  b  the  end  of  a  wire  moving  in  the  opposite  direction,  the 
e.m.f. 'sin  these  two  wires  will  be  in  opposite  directions.  The 


16 


HANDBOOK    ON    ENGINEERING. 


direction  of  the  e.m.f .  in  a  will  be  up  from  the  paper  toward 
the  observer,  and  the  direction  of  the  e.m.f.  in  b  will  be  down 
through  the  paper.  If  these  two  wires  are  secured  to  a  shaft 
placed  in  the  center  of  the  field,  then  by  the  continuous  rotation 


Figs.  23  and  24.    Illustrating  the  principle  of  the  armature. 

of  the  shaft,  the  two  wires  can  be  made  to  revolve  around  the 
circular  path  shown. 

If  these  two  wires  are  joined  at  the  ends,  as  shown  in  Fig.  24, 
they  will  form  a  closed  loop,  and  although  the  direction  of  the 
induced  e.m.f.  in  the  two  sides  will  be  opposite,  when  compared 
to  a  fixed  point  in  space,  they  will  be  in  the  same  direction  so 
far  as  the  loop  is  concerned ;  that  is,  both  e.m.f.'s  will  develop 
currents  that  will  flow  through  the  wire  in  the  same  direction. 

Returning  to  Fig-  23  it  will  be  noticed  that  if  the  wires  re- 
volve around  the  circular  path  at  a  uniform  velocity,  their  move- 
ment in  the  direction  of  line  c  c  will  not  be  uniform,  but  will  be 
the  greatest  when  the  wires  are  in  the  position  shown,  and  least, 
when  they  cross  the  line  c  c.  In  fact,  when  the  wires  cross  line 
c  c  their  motion  in  the  direction  of  this  line  will  be  zero,  for  this 


HANDBOOK    ON    ENGINEERING.  17 

is  the  point  where  the  direction  of  movement  reverses  No* 
the  magnitude  of  the  e.m.f.  induced  in  the  wire  is  proportional' 
to  the  veloorty  in  the  direction  of  the  line  c  c,  hence,  when  the 
wires  are  crossing  this  line,  the  e.m.f.  will  be  zero,  and  when 
they  are  one-quarter  of  a  turn  ahead  of  the  line,  the  e.ra.f  will 
be  the  highest. 

In  Fig.  24  we  see  that  in  side  «,  the  direction  of  the  current 
is  toward  the  front,  and  in  6  it  is  the  reverse;  now,  when  « 
moves  through  half  a  turn,  it  will  take  the  place  of  b,  and  the 
direction  of  the  e.m.f.  induced  in  it  will  be  the  same  as  in  b  in 
the  figure  ;  that  is,  it  will  be  the  reverse  of  what  it  is  when  pass- 
ing  in  front  of  the  pole  N.  This  being  the  case,  it  is  evident 
that  each  time  the  loop  makes  a  half-revolution,  the  direction  of 
the  current  generated  in  it  reverses. 


Fig.  25.    Arrangement  of  the  collector  rings. 


As  the  loop  in  Fig.  24  is  closed,  the  current  generated  in  it 
would  be  of  no  practical  value,  but  if  we  cut  the  wire  at  one 
side  and  connect  the  ends  with  rings  as  shown  at  a  and  b  in  Fig. 
25,  then  by  means  of  collecting  brushes  c  c  we  can  take  the  cur- 


18 


HANDBOOK    ON    ENGINEERING. 


rent  off  through  the  wires  d  d.  This  current,  however,  would 
consist  of  a  series  of  impulses  that  would  flow  in  opposite  direc- 
tions, each  one  starting  from  nothing  and  increasing  to  its  greatest 


Fig.  26.    Construction  of  simple  commutator. 


strength  when  the  loop  reaches  the  position  shown  in  the  figure, 
and  then  declining  and  reaching  the  zero  value  when  the  loop 
reaches  the  vertical  position.  Such  a  current  is  called  an  alter- 
nating current,  because  it  flows  first  in  one  direction  and  then  in 
the  opposite  direction.  All  forms  of  machines  that  generate  cur- 
rents by  electromagnetic  induction,  develop  alternating  currents, 
but  in  the  class  of  machines  known  as  direct  or  continuous  current, 
a  rectifying  device  is  used  which  rectifies  the  current  before  it 
reaches  the  external  circuit.  This  rectifying  device  is  called  a 
commutator,  and  is  illustrated  in  its  simplest  form  in  Fig  26.  In 
this  illustration  it  will  be  noticed  that  the  ends  of  the  wire,  instead 
of  being  attached  to  two  independent  rings,  placed  side  by  side, 
are  secured  to  two  half-rings,  placed  opposite  each  other.  The 
brushes  c  d,  through  which  the  current  is  taken  off,  are  held 
stationary ;  therefore,  as  can  be  readily  seen,  c  will  make  contact 


HANDBOOK    ON    ENGINEERING.  19 

with  a  during  one-half  of  the  revolution,  and  with  b  during  the 
other  half  ;  and  this  will  also  be  the  case  with  brush  d.  Now,  as 
the  half-rings  with  which  the  brushes  are  in  contact  change  at 
each  half  revolution,  it  follows  that  by  properly  setting  the 
brushes,  they  can  be  made  to  pass  from  one-half  ring  to  the  other 
at  the  very  instant  when  the  direction  of  the  current  in  the  loop 
reverses,  so  that  through  each  brush  there  will  be  a  succession  of 
current  impulses,  but  all  in  the  same  direction. 

The  device  shown  in  Fig.  25  is  a  perfect  alternating  current 
generator,  and  that  shown  in  Fig.  26  is  a  perfect  direct  current 
generator.  In  both  cases,  however,  the  e.m.f.  induced  is  so 
low  as  to  be  of  no  practical  value.  To  obtain  serviceable 
machines,  capable  of  developing  the  e.m.f.  and  current  strength 
required  in  practice,  it  is  necessary  to  provide  very  strong  mag- 
netic fields  and  to  rotate  in  these  a  large  number  of  loops  of  wire. 
In  order  that  the  operation  of  such  machines  may  be  understood, 
we  will  first  show  how  the  powerful  magnetic  fields  are  obtained. 

In  Fig.  27  two  wires  are  shown  as  seen  from  the  end,  these 
being  marked  A  and  B.  The  lines  of  force  surrounding  them  are 


m ' 

*^^4t  fa  J  \  v  \^ — 'o-**^~~^'       /< 

i_  '^'^4-J '  ^  \   \        ^  — "^       ^*~-**"^s         / 

:^—'*1'  i          \\    v I    X^    / 


Figs.  27  and  28.    Effects  of  direction  of  current  in  wires. 


in  directions  that  correspond  to  opposite  directions  of  current  in 
the  wires.  In  wire  A,  the  current  flows  away  from  the  observer. 
As  can  be  seen,  the  lines  of  force  of  both  wires  have  to  crowd  into 


20  HANDBOOK    ON    ENGINEERING. 

the  space  between  the  wires,  for  on  the  outside  of  A  the  two  sets 
of  lines  would  meet  each  other  head  on,  and  this  would  also  be 
the  case  on  the  right  side  of  wire  JB.  This  crowding  of  the  lines, 
of  force  into  the  space  between  the  wires  causes  them  to  distort 
from  their  natural  position  and  instead  of  being  central  with  the 
wires,  are  eccentric  to  them.  If  we  take  a  long  wire  through 
which  a  current  is  flowing  and  bend  it  into  a  loop,  we  will  see 
that  if  the  current  flows  out  through  one  side,  it  will  return 
through  the  other  side,  so  that  in  the  two  sides  of  the  loop  the 
current  will  flow  in  opposite  directions.  This  being  the  case, 
Fig.  27  can  be  regarded  as  showing  the  two  sides  of  such  a  loop, 
and  from  it  we  find  that  the  effect  of  such  a  loop  is  to  concentrate 
within  its  interior  nearly  all  the  lines  of  force  that  surround  the 
wire. 

In  Fig*  28  the  two  wires  A  and  B  are  surrounded  with  lines 
of  force  that  correspond  to  the  same  direction  of  current.  In 
this  case  it  will  be  noticed  that  in  the  space  between  the  wires  the 
lines  of  force  flow  in  opposite  directions  ;  hence,  only  a  few  of  the 
lines  will  follow  this  path,  simply  that  number  surrounding  each 
wire  that  can  traverse  the  space  without  encroaching  upon  the 
path  of  the  lines  belonging  to  the  other  wire.  If  the  two  wires 
are  very  near  to  each  other  i  practically  all  the  lines  of  force  of 
both  wires  will  join  forces,  so  to  speak,  and  pass  around  the  two 
wires.  Now,  if  we  wind  a  wire  into  a  coil  of  many  turns,  the 
direction  of  the  current  in  the  several  turns  will  be  the  same,  so 
that  the  lines  of  force  of  all  the  turns  will  combine  into  one  large 
stream  and  circulate  around  the  entire  coil  side,  no  matter  how 
many  turns  of  wire  it  may  contain.  From  this  it  can  be  seen 
that  if  we  have  a  current  of ,  say, ten  amperes,  we  can  make  it 
produce  just  as  powerful  magnetic  effect  as  a  current  of  one 
thousand  amperes,  by  simply  increasing  the  number  of  turns  of 
wire  in  the  coil.  A  current  of  ten  amperes  passing  through  a  coil 
of  wire  containing  one  hundred  turns,  will  have  the  same  magnet- 


HANDBOOK    ON    ENGINEERING.  21 

ism  in  effect,  as  a  current  of  one  hundred  amperes  passing  through 
a  coil  of  ten  turns,  or  as  a  current  of  one  thousand  amperes  pass- 
ing  through  a  coil  of  a  single  turn. 

If  we  place  at  the  side  of  a  wire  through  which  an  electric 
current  is  flowing  a  piece  of  iron,  as  is  shown  in  Fig.  29,  the 
effect  will  be  that  the  lines  of  force  will  no  longer  flow  in  circular 
paths,  as  indicated  by  the  circle  a,  but  will  be  deflected  in  the 
manner  illustrated,  by  the  presence  of  the  iron.  If,  instead  of 


Figs.  29  and  30.    Lines  of  force  through  wires  and  magnets. 

the  straight  iron  bar,  we  substitute  a  ring  of  iron,  as  in  Fig.  30, 
nearly  all  the  lines  of  force  will  be  concentrated  in  the  metal,  and 
the  magnetic  field  in  the  space  (7,  between  the  ends  of  the  ring, 
will  be  vastly  greater  than  at  any  other  point.  The  explanation 
of  these  actions  is  that  all  forms  of  matter  oppose  .the  develop- 
ment of  magnetic  force,  but  some  offer  greater  resistance  than 
others.  Iron,  steel,  nickel,  and  one  or  two  other  metals,  offer 
less  resistance  to  the  magnetic  lines  of  force  than  air,  and  are 
said  to  have  a  higher  magnetic  permeability.  Nickel  is  only  a 
slight  improvement  on  air,  but  steel  and  iron  are  far  superior, 
iron  being  of  about  two  to  three  times  the  permeability  of  hard- 


22 


HANDBOOK    ON    ENGINEERING. 


ened  steel,  and  about  one  thousand  times  the  permeability  of  air, 
when  magnetized  to  the  density  ordinarily  used  in  practice.  The 
iron  in  Figs.  29  and  30,  therefore,  becomes  the  path  of  the  lines 
of  force,  because  it  interposes  a  much  lower  resistance.  Owing 
to  this  difference  in  the  resistance  of  iron  and  air,  it  is  possible 
to  make  an  iron  magnet  core  of  any  desired  form,  and  to  con- 
centrate within  it  nearly  all  the  lines  of  force  developed  by  the 
current  flowing  through  the  wire  wound  upon  it.  The  presence 
of  the  iron  not  only  serves  to  concentrate  the  magnetism  in  it, 
but  as  it  reduces  the  resistance  opposing  the  development  of 
the  magnetism,  it  enables  the  field  to  be  made  vastly  stronger 
than  it  could  be  with  air  alone,  say  a  thousand  times  as  great. 

If  we  make  &  magnet  in  the  form  of  Fig.  31,  with  a  coil  of 
wire  around  the  part  jB,  practically  all  the  lines  of  force  will  flow  to 


Fig.  31.    Principle  of  construction  of  bipolar  machine. 

the  poles  N  $,  and  will  pass  through  the  air  space  between  them. 
If  this  air  space  is  nearly  filled  with  a  cylindrical  mass  of  iron,  A, 
the  strength  of  the  magnet  will  be  increased,  for,  by  doing  this, 


HANDBOOK    ON    KNU1NKKR1NU.  23 

we  replace  air  which  is  a  poor  magnetic  conductor,  by  iron  wliieh 
is  a  far  superior  conductor.  Electric  motors  and  generators  are 
made  with  a  cylindrical  mass  of  iron  at  A,  which  is  the  armature 


Fig.  32.    Solid  core. 


Ring  core. 


core,  and  the  air  space  between  it  and  the  faces  of  the  poles  of  the 
field  magnet  is  made  just  sufficient  to  accommodate  the  wire 
coils,  and  by  this  means  the  field  strength  is  increased  as  much  as 
possible. 

The  armature  cores  are  sometimes  made  solid,  as  in  Fig.  32, 
and  sometimes  as  a  ring,  as  in  Fig.  33.  When  they  are  solid, 
the  lines  of  force  cross  through  them  in  straight  lines,  see  Fig. 
32  ;  and  when  they  are  ring  form,  the  lines  follow  the  ring  and  do 
not  penetrate  the  interior  space. 

If  the  single  loop  of  Fig.  24  is  replaced  by  a  coil  containing 
many  turns  of  wire,  the  e.m.f.  induced  in  it  will  be  increased  in 
proportion  with  the  number  of  turns  of  wire  in  the  coil,  so  that  by 
using  such  a  coil  in  a  field  such  as  shown  in  Fig.  31,  a  high 
e.m.f.  can  be  obtained.  This  e.m.f.,  however,  would  be  alter- 
nating, and  if  the  current  were  rectified  by  means  of  a  commu- 


24  HANDBOOK    ON    ENGINEERING. 

tator,  it  would  not  be  of  uniform  strength,  but  would  fluctuate 
from  a  maximum  value  to  zero.  Just  how  the  current  would 
fluctuate  and  how  the  construction  can  be  changed  so  as  to  get  rid 
of  the  fluctuation,  we  can  explain  by  presenting  a  diagram  that 
illustrates  the  alternating  current  as  it  flows  in  the  armature  coil, 
and  the  rectified  current  as  it  leaves  the  commutator. 

In  Fig*  34>  let  the  distance  /  /*,,  h  i,  i  w,  along  the  line// 
represent  half -revolutions  of  the  coil,  and  let  distances  measured 
on  the  vertical  line  c  d  represent  the  strength  of  current,  distances 
above/  being  current  flowing  in  one  direction,  and  distances  below 
/being  for  current  flowing  in  the  opposite  direction.  Let  us  con- 
sider the  instant  when  the  coil  is  passing  the  point  where  the 
e.m.f.  induced  is  zero ;  then  this  instant  will  be  represented 
by  the  point  /,  at  the  left  of  the  diagram,  and  the  curve  a 
will  start  from  this  point ;  as  at  that  instant,  the  current  which  it 
represents  has  no  value.  As  the  coil  rotates,  the  current  begins 
to  grow,  and  this  fact  we  indicate  by  causing  curve  a  to  gradually 


Figs.  34  and  35.    Illustrating  flow  of  alternating  current. 


rise  above  the  horizontal  line.  At  the  quarter  turn,  the  current 
reaches  its  greatest  strength,  thus  this  forms  the  highest  point  of 
curve  a,  and  is  midway  between  /  and  h.  From  this  point 


HANDBOOK    ON    ENGINEERING.  25 

onward,  the  current  declines  and  becomes  zero,  when  the  rotation 
of  the  coil  has  reached  one-half  of  a  revolution,  which  is  repre- 
sented by  the  point  h.  In  the  next  half -revolution,  the  current 


Fig.  86.  Two  coils  on  armature.     Fig.  37.  Four  coils  on  armature. 


flows  in  the  reverse  direction,  but  has  the  same  maximum  strength 
and  increases  and  decreases  at  the  same  rate;  therefore,  the  curve 
6,  drawn  below  the  horizontal  line,  represents  the  reverse  current ; 
and  point  i  corresponds  to  one  complete  revolution,  so  that 
beyond  i  the  curves  a  and  b  are  repeated  in  systematic  order. 

Now,  if  we  provide  a  commutator  to  rectify  this  current,  all 
we  can  accomplish  is  to  turn  curve  b  upside  down  and  transfer  it 
to  the  upper  side  of  the  horizontal  line,  as  in  Fig.  35 ;  but,  as 
will  be  seen,  all  we  accomplish  by  this  act  is  to  obtain  a  current 
that  flows  always  in  the  same  direction,  but  at  each  half-revo- 
lution it  drops  down  to  a  zero  value. 

If  we  wind  two  coils  upon  the  armature,  placing  them  at  right 
angles  with  each  other,  as  is  indicated  by  A  and  B  in  Fig.  36, 
then  if  the  currents  of  these  two  coils  are  rectified,  they  will  bear 
the  relation  toward  each  other  shown  at  the  upper  line  in  Fig.  38, 
the  a  a  curves  in  solid  lines  representing  the  current  from  the  A 
coil,  and  the  b  b  curves  in  broken  lines,  representing  the  current 
from  the  B  coil.  As  will  be  seen,  when  one  of  these  currents  is 
zero,  the  other  is  at  its  greatest  value,  so  that  if  we  run  both  into 


26 


HANDBOOK    ON    ENGINEERING. 


the  same  circuit,  the  lowest  value  of  the  combined  current  would 
be  equal  to  the  maximum  of  either  one  of  the  single  currents, 
and  the  maximum  value  would  be  equal  to  the  sum  of  the  two 
currents  when  the  coils  are  on  the  eighths  of  the  revolution. 


Fig.  38.    Showing  effect  of  larger  number  of  coils. 

This  resulting  current  is  shown  on  the  lower  line  in  Fig.  38  by 
the  curve  d  d.  From  this  curve  we  see  that  the  number  of 
fluctuations  in  the  current  has  been  doubled,  but  the  variation  in 
the  strength  is  greatly  reduced.  If  we  wound  four  coils  upon 
the  armature,  as  indicated  by  A  B  C  Z>,  in  Fig.  37,  the  number 
of  undulations  in  the  combined  current  would  be  again  doubled, 
but  the  fluctuation  would  be  very  much  less.  If  the  number  of 
coils  is  increased  to  twenty-five  or  thirty,  the  fluctuations  in  the 
current  become  so  small  as  to  be  hardly  worth  noticing. 

With  coils  such  as  shown  in  Fig.  26,  a  separate  commutator 
would  have  to  be  provided  for  each  coil,  and  this  would  render 
the  machine  very  complicated,  if  the  number  of  coils  were  even 
six  or  eight ;  hence,  in  actual  machines,  the  winding  of  the  coils 
is  modified  so  as  to  be  able  to  use  a  single  commutator  for  any 
number  of  coils.  This  construction  will  be  explained  in  the 
next  chapter. 


HANDBOOK    ON    KNOINKKRING. 


27 


CHAPTER     III. 
TWO  POLE  GENERATORS  AND  MOTORS. 

The  simplest  type  of  armature  winding  is  that  used  with  ring 
cores,  and  is  illustrated  in  Fig.  39.  As  will  be  seen,  it  is  simply 
a  continuous  winding  all  the  way  around  the  circle,  the  end  of 
the  last  turn  of  wire  being  connected  with  the  beginning  of  the 
first  turn,  so  as  to  form  an  endless  coil.  If  wires  are  attached  at 
a  and  &,  and  a  current  is  passed  through,  it  will  divide  into  two 
halves,  one  part  flowing  through  the  wire  above  a  6,  and  the  other 
part  through  the  wire  below  a  b.  In  the  upper  half  of  the  wire, 
the  direction  of  the  current  in  the  front  sides  of  the  turns  will  be 
toward  the  center  of  the  ring,  as  is  indicated  by  the  arrow  heads, 
and  in  the  lower  half  it  will  be  away  from  the  center.  If,  in- 


Figs.  39  and  40.    Windings  on  ring  armatures. 

stead  of  attaching  wires  at  a  and  b  we  place  stationary  springs,  so 
as  to  press  against  the  wire,  then  we  could  revolve  the  ring,  and 
still  the  current  would  enter  and  leave  the  wire  at  the  same  points. 
Small  armatures  are  often  made  in  this  way,  but  for  regular 


28  HANDBOOK    ON    ENGINEERING. 

. 

machines  it  is  more  desirable  to  provide  a  commutator  as  shown 
in  Fig.  40  at  (7,  and  then  the  several  segments  can  be  connected 
with  the  wire  at  regular  intervals.  In  the  figure,  the  commutator 
is  provided  with  twelve  segments,  and  these  connect  with  the 
armature  wire  at  every  fourth  turn,  so  that  the  wire  is  divided 
into  twelve  coils  of  four  turns  each. 

The  only  difference  between  this  diagram  and  a  regular  gen- 
erator armature  of  the  ring  type,  is  that  it  shows  the  wire  coils 
spread  out  with  a  considerable  space  between  them,  and  only  in 
one  layer,  while  in  the  actual  machine,  the  wire  is  wound  close 
together  and  generally,  in  several  layers;  but  no  matter  how  many 
layers  there  may  be,  or  how  many  turns  in  a  coil,  the  principle  of 
winding  is  the  same. 

We  have  shown  the  ring  winding  first,  because  it  is  so  simple 
that  it  can  be  understood  with  the  most  superficial  explanation. 
The  drum  winding,  which  is  used  to  a  much  greater  extent,  is  the 
same  in  principle  as  the  ring,  but  owing  to  the  fact  that  the  coils 
cross  each  other  at  the  ends,  it  appears  to  be  decidedly  different. 
By  the  aid  of  Figs.  41  to  44,  the  drum  winding  can  be  made  per- 
fectly clear. 

Fig,  4J  shows  a  ring  armature  core  with  a  single  coil  wound 
upon  it ;  and  Fig.  42  shows  a  drum  core,  with  a  single  coil  wound 
upon  it.  In  the  ring,  only  one  side  of  the  coil  appears  upon  the 
outer  surface  of  the  armature,  but  in  the  drum,  as  there  is  no 
open  space  for  the  coil  to  thread  through,  both  sides  of  the  coil 
must  be  placed  upon  the  outer  surface.  The  side  B  of  the  coil 
may  be  called  the  live  side,  as  it  is  the  one  from  which  the  ends 
project,  and  the  lower  side  c,  may  be  called  the  dead  side.  Since 
only  the  live  side  of  the  coil  has  ends  to  be  connected,  it  can  be 
readily  seen  that  if  in  the  drum  winding  we  leave  spaces  between 
the  live  sides  for  the  dead  sides,  and  then  connect  the  ends  of  the 
live  sides  by  jumping  over  the  dead  side  between  them,  that  we 
will  have  the  same  order  of  connection  as  in  the  ring  winding. 


HANDBOOK    ON    ENGINEERING. 

b 


29 


Fig.  41.    Ring  armature  core.          Fig.  42.    Drum  armature  core. 


The  dead  side  of  each  coil  adjoins  the  live  side  of  a  coil  that  is,  in 
reality,  half  a  circumference  away  from  it;  thus,  in  Fig.  43,  the 
live  side  of  coil  a  is  at  the  top  and  the  dead  side  is  at  the  bottom  ; 
while  the  live  side  of  coil  n  is  at  the  bottom  and  the  dead  side  is 
at  the  top.  The  live  sides  of  these  two  coils  are  on  opposite  sides 
of  the  armature,  so  that  the  coil  side  to  the  right  of  a  is  simply 


Figs.  43  and  44.    Windings  of  drum  armature. 


30  HANDBOOK    ON    ENGINEERING. 

the  dead  side  of  a  coil  whose  live  side  is  on  the  other  side  of  the 
armature.  In  Fig.  44  the  two  coils  a  and  b  are  adjoining  coils, 
for  the  coil  side  between  them  is  the  dead  side  of  coil  n,.  To  con- 
nect the  armature,  therefore,  we  join  end  2  of  coil  a  with  end  1 
of  coil  Z>,  and  the  end  2  of  coil  b  would  jump  over  a  dead  sjdeand 
connect  with  end  1  of  coil  c.  Coil  c,  however,  would  appear  to 
be  two  coils  ahead  of  £>,  just  as  b  appears  to  be  two  coils  ahead 
of  a. 

In  winding  drum  armatures,  the  coils  are  generally  placed  in 
pairs,  as  shown  in  Fig.  43  and  also  in  Fig.  44.  The  object  of 
this  is  simply  to  make  the  ends  of  the  armature  look  more  even. 
A  drum  armature  can  be  wound  out  of  a  continuous  wire,  by 
simply  making  a  loop  to  take  the  place  of  the  ends  1  and  2,  and 
then  skipping  a  space,  as  shown  by  coils  a  and  b  in  Fig.  44.  After 
the  armature  is  half  covered,  there  will  be  spaces  left  between  the 
coils,  these  spaces  being  of  the  width  of  a  coil ;  we  then  proceed 
to  fill  up  the  vacant  spaces,  and  when  they  are  all  filled,  the  last 
coil  put  in  will  be  the  proper  position  to  connect  with  the  first 
one  wound.  A  little  practice  with  a  piece  of  twine  and  a  wooden 
cylinder,  will  enable  any  one  to  find  out  in  short  order  how  to 
wind  drum  armatures. 

The  two  types  of  winding  just  explained,  are  those  used 
with  two  pole  machines,-  motors  as  well  as  generators.  It  may 
be  added  that  there  is  no  difference,  electrically,  between  a  motor 
and  a  generator,  and  any  machine  can  be  used  for  either  service. 
Motors,  however,  are  somewhat  modified  in  design  so  as  to  make 
them  more  suited  to  the  work  they  have  to  perform.  The  modi- 
fication consists  mainly  in  protecting  the  parts  liable  to  be  injured 
by  objects  falling  upon  them. 

The  general  arrangement  of  the  field  and  armature  in  a  two 
pole  machine  is  shown  in  Fig.  31.  The  design  can  be  changed  in 
a  vast  number  of  ways,  but  it  will  always  be  two- pole,  or  bipolar, 
as  it  is  called,  if  only  two  poles  are  presented  to  the  armature. 


HANDBOOK    ON    ENGINEERING. 


31 


Generators  and  motors  are  arranged  so  that  the  current  that 
magnetizes  the  field  may  be  the  whole  current  that  flows  in  the 
circuit,  or  only  a  part  of  it.  When  the  whole  current  passes 
through  the  field  magnetizing  coils,  the  machine  is  said  to  be  of 
the  series  type  ;  this  name  being  given  because  the  armature  wire 
and  the  field  coils  are  connected  in  series,  so  that  the  current  first 
passes  through  one  and  then  through  the  other.  If  the  field 
coils  are  traversed  by  only  a  portion  of  the  current,  the  machine 


Fig.  45.  Showing  series  connection.  Fig.  46.  Showing  shunt  connection. 

is  said  to  be  of  the  shunt  type,  owing  to  the  fact  that  the  field  is 
supplied  with  a  current  that  is  shunted  from  the  main  circuit. 
Generators  and  motors  are  also  arranged  so  that  there  are  two 
sets  of  field  coils  and  one  is  traversed  by  the  whole  current,  and 
the  other  by  a  portion  thereof.  The  best  way  to  understand 
these  different  types  of  connection  is  by  means  of  simple  diagrams 
that  show  the  wire  coils  of  the  field  and  the  outline  of  the  arma- 
ture. Such  diagrams  are  presented  in  Figs.  45  to  50.  Fig.  45 


32 


HANDBOOK    ON    ENGINEERING. 


represents  the  series  connection,  A  being  the  armature,  C  the 
commutator,  and  M  the  field  coil.  The  direction  of  the  current 
is  indicated  by  the  arrow  heads.  Fig.  46  is  the  shunt  connection, 
and  the  arrow  heads  show  the  direction  of  the  currents  in  the  case 
of  a  generator.  As  will  be  seen,  at  d  the  field  current  branches 
off  from  the  main  line  and  returns  to  it  at  a,  after  having  passed 
through  the  field  coil.  Fig.  47  shows  the  type  in  which  the  field  is 
magnetized  by  two  sets  of  coils,  one  being  in  series  with  the  main 
circuit  and  the  other  in  shunt.  As  will  be  noticed,  all  the 
armature  current  passing  out  through  wire  d,  goes  through  coil 
F,  except  the  portion  that  is  shunted  at  c,  into  the  shunt  coil  M. 
This  type  of  winding  is  called  compound,  being  a  combination 
of  the  series  and  shunt.  When  the  shunt  coil  is  connected  as  in 


Fig.  47.    Field  magnetized  by  two  sets  of  coils. 

Fig.  48.    Illustrating  long  shunt. 

Fig.  47,  it  is  called  a  short  shunt,  and  when  as  in  Fig.  48,  it  is  a 
long  shunt.  In  the  first  case,  the  coil  M  shunts  the  armature 
only,  and  in  the  second,  it  shunts  the  coil  F  also. 


HANDBOOK    ON    ENGINEERING.  33 

Figs*  49  and  50  show  the  shunt  and  compound  types  for 
motors,  and  as  will  be  noticed,  the  only  difference  between  them 
and  the  generator  diagrams,  is  that  the  direction  of  the  current 


Fig:.  49.    Shunt  type  of  motor. 


Compound  type  of  motor. 


in  the  shunt  coils  is  not  the  same.  This  difference  in  direction  is 
due  to  the  fact  that  in  the  generator  the  armature  generates  the 
current  that  passes  through  coil  M;  hence,  at  point  d,  the  cur- 
rent flows  up  to  the  main  line  and  down  to  the  field  coil.  In  the 
motor,  the  current  comes  from  an  external  source  through  main 
7i,  and  thus  passes  from  a  to  the  armature,  and  also  to  the  field 
coil,  thus  traversing  the  latter  in  the  opposite  direction.  In  the 
series  coil  F,  the  direction  of  the  current  is  the  same  in  both 
machines. 

Generators  are  made  so  as  to  keep  the  strength  of  the  current 
constant,  and  allow  the  voltage  to  vary  as  the  demands  of  the 
service  may  require ;  or  they  may  be  wound  so  as  to  keep  the 
voltage  constant  and  allow  the  current  strength  to  vary.  Machines 


34  HANDBOOK    ON    ENGINEERING. 

of  the  first  class  are  called  constant  current,  and  are 
used  principally  for  arc  lighting.  Machines  of  the  second 
class  are  called  constant  potential  and  are  the  kind  used 
for  incandescent  lighting,  for  electric  railways  and  for  the 
operation  of  motors  of  every  description.  For  constant  current 
generators  the  series  winding  is  used  in  connection  with  some 
kind  of  regulating  device  that  prevents  the  current  strength  from 
varying  more  than  the  small  fraction  of  an  ampere.  The  shunt 
and  compound  windings  are  used  for  constant  potential  genera- 
tors. If  the  armature  wire  had  no  resistance,  the  shunt  winding 
would  enable  a  generator  to  maintain  a  constant  voltage  at  its 
terminals,  no  matter  how  much  the  strength  of  the  current  might 
vary ;  but  armatures  without  resistance  cannot  be  made ;  there- 
fore, a  shunt-wound  machine  will  develop  a  slightly  lower  voltage 
with  full  current  than  with  a  weak  one,  but  the  difference  will 
not  be  more  than  three  to  five  per  cent.  By  the  aid  of  the  com- 
pound winding,  the  generator  can  be  made  so  as  to  develop  the 
same  voltage  with  light  or  full  load,  and  if  desired,  the  voltage 
can  be  made  to  increase  as  the  current  increases.  If  a  com- 
pound generator  is  so  proportioned  that  the  voltage  is  the  same 
for  weak  and  strong  currents,  it  is  said  to  be  evenly-compounded, 
and  if  the  voltage  increases  as  the  current  increases,  it  is  said  to 
be  over-compounded.  If  the  voltage  is  five  per  cent  higher,  with 
full  load  than  with  no  load,  the  generator  is  said  to  be  over-com- 
pounded five  per  cent,  and  if  the  increase  is  ten  per  cent,  it  is 
said  to  be  over-compounded  ten  per  cent. 

The  way  in  which  a  compound  generator  increases  the  volt- 
age can  be  readily  understood  from  an  examination  of  Fig.  47. 
The  current  that  passes  through  the  shunt  coil  M,  is  practically 
one  of  the  same  strength  at  all  times ;  therefore,  the  magnet- 
izing effect  of  this  coil  does  not  change.  Through  coil  F  the 
whole  current  passes,  hence,  the  magnetizing  effect  of  this  coil 
increases  as  the  current  strength  increases.  Now  the  total  field 


HANDBOOK    ON    ENGINEERING.  35 

magnetism  is  that  due  to  the  combined  action  of  the  two  coils,  so 
that  as  the  action  of  F  increases,  the  strength  of  the  field  in- 
creases. If  F  has  only  a  few  turns  of  wire,  it  will  only  help 
slightly  to  magnetize  the  field ;  therefore,  its  increased  effect,  due 
to  increase  in  current,  will  not  be  very  noticeable  ;  but  if  F  has 
many  turns,  it  will  develop  a  large  proportion  of  the  field  magnet- 
ism, and,  under  this  condition,  the  change  in  current  strength 
will  make  a  decided  change  in  the  strength  of  the  field,  and  thus 
in  the  voltage,  for  the  voltage  is  directly  proportional  to  the 
strength  of  the  field. 

In  motors,  the  coil  F  can  be  connected  so  as  to  act  with 
coil  Jf,  or  against  it.  If  both  coils  act  together,  the  motor  is 
compound-wound  ;  and  if  F  acts  against  M,  the  motor  is  differ- 
entially-wound. A  compound- wound  motor  will  slow  down  more 
with  a  heavy  load  than  a  simple  shunt  machine,  but  it  will  carry 
the  load  with  a  smaller  current,  and,  on  this  account,  this  wind- 
ing is  commonly  used  for  elevator  motors.  A  differential  motor 
will  hold  up  the  speed  better  with  a  heavy  load  than  a  simple 
shunt  machine,  but  it  will  take  a  correspondingly  larger  current 
to  do  the  work.  The  differential  winding  is  not  used  to  any  great 
extent,  except  in  cases  where  it  is  desired  to  obtain  as  uniform  a 
velocity  as  possible. 

In  explaining  the  principles  of  armature  winding,  it  was  shown 
that  the  commutator  brushes  must  make  contact  with  the  com- 
mutator on  the  sides,  that  is,  that  in  Fig.  51,  they  would  be 
placed  on  the  diameter  n  n.  In  actual  machines,  they  are  either 
ahead  of  this  line,  as  in  Fig.  52,  or  back  of  it,  as  in  Fig.  53. 
The  first  position  is  that  of  the  generator  and  the  second  that  of 
the  motor.  The  reason  why  the  brushes  have  to  be  set  ahead  of 
line  n  n  in  a  generator,  and  back  of  the  line  in  a  motor,  is  that 
the  armature  current  develops  a  magnetization  of  its  own,  and  this 
reacts  upon  the  magnetism  of  the  field  so  as  to  twist  the  lines  of 
force  out  of  their  true  path.  If  we  look  at  Fig.  39,  we  can  see 


36  HANDBOOK    ON    ENGINEERING. 

that  the  direction  of  the  current  through  the  wires  is  such  that 
the  magnetizing  effect  produced  upon  the  armature  core  is  the 
same  as  it  would  be  if  the  wire  were  wound  in  the  way  indicated 
by  the  vertical  lines  in  Fig.  51.  Now  this  current  will  develop  a 
magnetization  in  the  direction  of  line  nn;  that  is,  at  right  angles 
to  the  field  magnetism.  These  two  magnetic  forces  of  the  arma- 
ture and  the  field,  engage  in  a  tug  of  war,  and  the  result  is  that 
the  actual  magnetization  that  acts  upon  the  armature  wire  is  the 
combined  effect  of  the  two. '  If  the  strength  of  the  field  magnetism 


Fig.  51.  Fig.  52.  Fig.  53. 

Showing  proper  position  of  brushes. 

is  proportional  to  line  c  a,  and  the  strength  of  the  armature  mag- 
netization is  proportional  to  line  c  &,  then  the  actual  magnetiza- 
tion will  be  equal  to  line  c  d,  and  in  the  direction  d  d.  In  Fig. 
52,  which  represents  a  generator,  if  the  current  in  the  field  coils 
passes  over  the  front  side  in  the  direction  of  arrow  *',  and  the 
armature  revolves  in  the  direction  of  arrow  cZ,  then  the  armature 
current  will  be  in  the  direction  of  arrow  /  and  the  armature  mag- 
netization will  be  in  the  direction  of  arrow  h.  The  field  magneti- 
zation will  be  from  N  to  $,  therefore,  the  resulting  magnetization 
will  be  in  the  direction  of  line  a  a.  Now  the  proper  position  for 


HAMDBOOK    ON    ENGINEERING. 


37 


the  brushes  is  on  a  line  at  right  angles  to  the  direction  of  the 
field,  hence,  they  mast  rest  upon  line  c  c.  If  the  machine  is  a 
motor,  the  only  change  effected  will  be  that  the  direction  of  the 
armature  current  will  be  reversed,  so  that  arrow  /  will  point 
downward  instead  of  upward,  and  the  magnetism  of  the  armature 
will  be  directed  to  the  right  as  shown  by  arrow  c.  Under  these 
conditions,  the  actual  direction  of  the  field  magnetism  will  be  that 
of  line  b  &,  and  upon  line  e  e,  at  right  angles  to  this  the  brushes 
must  be  set. 

WIRING  TABLE    FOR   110- VOLT,  16  CANDLE  POWER  LAMPS. 

(Size  of  Wire  in  B.  &  S.  Gauge.) 


«w  cc 

o  p, 

2* 

^^ 

DISTANCE  IN  FEET  TO  CENTER  OF  DISTRIBUTION. 

20 

25 

30 

35 

40 

45 

50 

60 

70 

80 

90 

100 

120 

140 

160 

180 

200 

2 

20 

19 

19 

19 

19 

19 

19 

19 

18 

18 

17 

16 

16 

15 

15 

14 

13 

3 

19 

19 

19 

19 

19 

18 

18 

17 

16 

16 

15 

15 

14 

13 

13 

12 

12 

4 

19 

19 

19 

18 

18 

17 

16 

16 

15 

14 

14 

13 

13 

12 

11 

11 

10 

5 

19 

19 

18 

17 

16 

16 

16 

15 

14 

14 

13 

13 

].'   11 

11 

10 

10 

6 

19 

18 

17 

16 

16 

15 

15 

14  14 

13 

13 

12 

11 

11 

10 

10 

9 

7 

18 

17 

16 

16 

15 

15 

14 

14 

13 

12 

12 

11 

11 

10 

9 

9 

8 

8 

18 

17 

16 

15 

15 

14 

14 

13 

12 

12 

11 

11 

10 

9 

9 

8 

8 

9 

17 

16 

15 

15 

14 

14 

13 

12 

12 

11 

11 

10 

9 

9 

8 

8 

7 

10 

17 

16 

15 

14 

14 

13 

13 

12 

11 

11 

10 

10 

9 

8 

8 

7 

7 

12 

16 

15 

14 

14 

13 

13 

12 

11 

11 

10 

10 

9 

8 

8 

7 

7 

6 

14 

15 

14 

13 

13 

12 

12 

11 

10 

10 

9 

9 

8 

7 

7 

6 

6 

5 

16 

15 

14 

13 

12 

12 

11 

11 

10 

9 

9 

8 

8 

7 

6 

6 

5 

5 

18 

14 

13 

12 

11 

11 

10 

10 

9 

9 

8 

8 

7 

6 

6 

5 

5 

4 

20 

14 

13 

12 

11 

11 

10 

10 

9 

8 

8 

7 

7 

6 

5   5 

4 

4 

25 

13 

12 

11 

10 

10 

9 

9 

8 

7 

7 

6 

6 

5 

4 

4 

3 

3 

30 

12 

11 

10 

10 

c 

8 

8 

7 

6 

6 

5 

5 

4 

a 

3 

3 

2 

35 

11  10 

10 

9   8 

8 

7 

7 

6 

K 

5 

4 

4 

3 

2 

2 

1 

40 

11 

10 

c 

8   8 

7 

7 

6 

5 

B 

4 

4 

3 

2 

1 

1 

1 

45 

10 

9 

8 

8   7 

7 

6 

5 

^ 

4 

4 

3 

2 

2 

1 

1 

0 

50 

9 

c 

8 

7 

7 

6 

6 

5 

4 

4 

3 

3 

2 

1 

1 

0 

0 

60   8 
70   7 

8 

7 

7 
7 

7 
6 

6 
5 

6 
5 

5 
4 

4 
4 

CO  CO 

c 
o 

2 

2 

2 

2 
1 

1 

1 

1 
0 

0 
0 

80 

6l  6 

6 

5 

5 

4 

4 

3 

2 

2 

1 

1 

u 

0 

90 

6 

6 

f 

5 

4 

4 

J 

2 

2 

1 

1 

0 

0 

100 

5 

5 

5 

4 

4 

3 

3 

2 

1 

1 

0 

0 

38 


HANDBOOK    ON    ENGINEERING. 


CHAPTKJLt      IV. 
MULTIPOLAR  MACHINES. 

The  only  difference  between  a  bipolar  and  multi polar  machine 
is,  that  the  latter  has  two  poles,  and  the  former  has  two  or  more 
pairs  of  poles.  In  consequence  of  this  difference  in  the  number 


Fig.  54.    Showing  four-pole  machine. 

of  poles,  the  armature  winding  has  to  be  slightly  modified,  as  will 
be  presently  explained.     Fig.  54  illustrates  a  four-pole  machine 


HANDBOOK    ON    ENGIN BERING. 


39 


and,  as  will  be  noticed,  the  N  and  S  poles  alternate  around  the 
circle.  This  arrangement  is  followed,  no  matter  what  the  number 
of  poles  may  be. 

The  advantage  of  the  multipolar  construction  is  that  it  in- 
creases  the  capacity  of  the  machine  for  a  given  size  and  weight. 
Figs.  55  to  57  illustrate  the  gain  effected  in  weight.  The  first 
figure  shows  a  two-pole  machine,  the  second  a  four-pole  and  the 
third  an  eight-pole,  the  three  being  of  the  same  capacity.  The 
poles  of  the  second  machine  are  half  as  wide  as  those  of  the  first, 
as  there  are  twice  as  many.  The  other  parts  are  reduced  in  like 
proportion.  In  Fig.  57,  the  poles  are  one-quarter  as  wide  as  in 


Fig.  55.  Fig.  56.  Fig.  57. 

Effect  of  increasing  the  Dumber  of  poles. 

Fig.  55,  as  there  are  four  times  as  many.  On  account  of  the 
reduction  in  the  width  of  the  poles,  the  armatures  can  be  increased 
in  diameter  as  the  number  of  poles  is  increased,  without  increas- 
ing the  outside  dimensions  of  the  machine,  so  that  in  reality, 
Fig.  56  is  somewhat  more  powerful  than  Fig.  55,  and  Fig.  57  is 
still  more  powerful. 

The  fields  of  multipolar  machines  are  wound  the  same  as 
those  of  the  bipolar ;  that  is,  as  series,  shunt  or  compound. 
Figs.  58  to  60  show  the  three  types  of  winding  for  a  four-pole 
machine  and  Fig.  61  is  a  diagram  of  compound  winding  for  an 
eight-pole  generator.  The  number  of  commutator  brushes  used  is 
equal  to  the  number  of  poles,  although  with  one  type  of  armature 


40 


HANDBOOK    ON    ENGINEERING. 


winding,  two  brushes  are  sufficient,  no  matter  how  many  poles 
the  machines  may  have.  In  practice,  however,  even  with  this 
winding,  the  number  of  brushes  is  generally  made  equal  to  the 
number  of  poles. 

With  a  four-pole  machine  the  brushes  can  be  connected  in  a 
simple  manner,  as  shown  in  Figs.  58  to  60,  but  with  a  greater 
number  of  poles,  two  rings  are  generally  provided,  to  which  the 
brushes  are  connected  in  the  manner  shown  in  Fig.  62. 


Figs.  58  and  59.    Connection  of  brushes  on  four-pole  machine. 


Looking  at  Fig.  54,  it  can  be  seen  that  if  the  current  flows  up 
from  the  paper,  under  the  N  poles,  it  will  flow  down  through  the 
paper,  under  the  S  poles ;  hence,  the  armature  coils  in  a  four- 
pole  machine  must  span  only  one-quarter  of  the  circumference, 
and  not  one-half,  as  in  the  two-pole  armature.  For  a  six-pole 
armature,  the  coils  must  span  one-sixth  of  the  circumference, 
and  for  an  eight-pole,  one-eighth,  and  so  on,  for  any  higher 
number  of  poles. 

There  are  two  types  of  winding  for  multipolar  armatures,  one 
being  called  the  lap,  or  parallel  winding,  and  the  other  the  wave 


HANDBOOK   ON   ENGINEERING. 


41 


42 


HANDBOOK    ON    ENGINEERING. 


or  series  winding.     Fig.  62  is  a  diagrammatic  illustration  of  the 
lap  winding,  and  Fig.  63  of  the  wave  winding,  both  for  four  poles. 


Fig.  62.    Diagram  of  lap  winding. 

The  small  circles  around  the  outside  of  the  armature  represent 
bars  or  wires,  which  are  connected  with  the  commutator  segments 
by  means  of  the  solid  lines,  and  with  each  other  at  the  opposite 
side  of  the  armature,  by  means  of  the  broken  lines. 

If  we  start  from  coil  side,  or  bar  1  on  the  left,  and  follow  the 
connections  as  guided  by  the  numbers,  we  will  finally  reach  32, 
and  thus  come  back  to  left  side  brush  a,  which  is  the  starting 
point.  As  will  be  seen,  bar  1  connects  at  the  back  of  armature, 


HANDBOOK    ON    ENGINEERING. 


43 


with  bar  2,  and  then  over  the  front,  the  connection  runs  in  the 
backward  direction,  to  bar  3  ;  thence,  forward  again,  at  the  back 
end,  to  bar  4,  and  again  backward  over  the  front,  to  bar  5.  The 
connections,  therefore,  lap  over  each  other  and  it  is  on  this 
account,  that  it  is  called  a  lap  winding. 

Fig*  63  shows  the  wave  winding,  and  it  will  be  noticed  that  if 
we  start  from  bar  1  at  the  top,  we  advance  around  the  right  to  bar 
2,  and  then  we  go  further  ahead  to  bar  3,  and  in  like  manner 
advance  to  bar  4,  the  connections  in  every  case  advancing  in  the 


Fig.  63.    Diagram  of  wave  win 

same  direction  around  the  circle.     It  will  be  further  noticed  that 
the  connections  run  zig-zag  from  side  to  side  of  the  armature  core 


44  HANDBOOK    ON    ENGINEERING. 

as  they  advance,  thus  forming  a  wave-like  path  for  the  current, 
and  it  is  on  this  account  that  this  style  of  connection  is  called 
wave  winding. 

With  the  lap  winding,  the  brushes  a  a  are  connected  with  each 
other,  and  so  are  the  b  b  brushes.  In  the  wave  winding,  two 
brushes  set  one-quarter  of  the  circle  from  each  other,  will  take 
the  current  off  properly  as  indicated  by  a  and  b  in  Fig.  63,  but 
four  brushes  can  also  be  used. 

In  Fig*  54,  the  brushes  are  shown  midway  between  the  poles, 
while  in  Figs.  62  and  63,  they  are  opposite  the  poles.  This  dif- 
ference in  position  is  due  to  the  fact  that  in  the  last  two  named 
figures,  the  connections  between  the  armature  coils  and  the  com- 
mutator segments  do  not  run  in  radial  lines  from  either  side,  but 
one  connection  bends  backward  and  the  other  forward.  In 
actual  machines,  the  connections  are  run  as  in  these  diagrams,  and 
in  some  cases,  one  of  the  sides  runs  in  a  radial  direction;  there- 
fore, in  some  generators,  the  brushes  are  opposite  the  poles,  and 
in  others  they  are  between  them. 

Diagrams  62  and  63  show  coils  of  a  single  turn,  but  by  regard- 
ing the  broken  lines  as  representing  the  position  of  the  end  of  the 
coil  at  front  as  well  as  the  back  of  the  armature,  and  the  solid 
lines  as  simply  the  ends  of  the  wire  that  connect  with  the  com- 
mutator segments,  they  become  accurate  representations  of  coils 
of  any  number  of  turns. 

The  coils  of  multipolar  armatures  are  made  on  forms,  and  in 
the  finished  state  are  placed  upon  the  armature  core.  Some  coils 
are  so  formed  as  to  bend  down  over  the  ends  of  the  armature,  and 
are  then  given  the  form  at  the  ends,  shown  in  Fig.  64,  so  they 
may  fit  into  each  other.  In  some  machines,  the  coils  do  not  bend 
down  over  the  ends  of  the  armature,  but  run  out  parallel  with 
the  shaft.  Armatures  so  wound  are  sometimes  said  to  have  a 
barrel  winding,  and  the  coils,  if  laid  out  upon  a  flat  surface, 
would  present  the  appearance  of  Fig.  65  ;  that  is,  if  they  con- 


HANDBOOK    ON    ENGINEERING. 

abed 


45 


Figs.  64  and  65.    Armature  windings. 

tained  more  than  one  turn.  If  of  the  single-turn  type,  they 
would  look  like  Fig.  66,  if  for  a  lap  winding;  and  like  Fig.  67, 
if  for  a  wave  winding,  the  ends  d  d  being  joined  and  then  con- 
nected with  the  commutator  segments. 

In  connecting   the  field    coils   of   multi polar   machines,  it   is 
necessary  to  be  careful  not  to  make  mistakes,  so  that  some  of  the 


abc 


ab  c 


d  '  'd  d 

Figs.  66  and  67.    Drum  and  barrel  windings 


46  HANDBOOK    ON    ENGINEERING. 

coils  will  act  to  magnetize  the  field  in  the  wrong  direction.  By 
studying  Fig.  27  and  the  explanation  of  it,  the  direction  of  the 
magnetic  lines  of  force  with  respect  to  the  direction  of  the  current 
through  the  magnetizing  coils,  can  be  clearly  understood,  and 
then  there  will  be  no  difficulty  in  determining  the  proper  way  in 
which  to  connect  the  coil  ends,  for  all  we  have  to  do  is  to  make 
the  connections  such  that  if  one  pole  is  N  the  one  next  to  it  is  S. 
With  two-pole  machines,  it  is  also  necessary  to  be  careful  not  to 
connect  the  field  coils  improperly;  that  is,  if  there  is  more  than 
one  coil,  and  in  most  machines  this  is  the  case. 

The  current  that  energizes  a  magnet  is  called  the  magnetizing 
force  and  is  measured  in  ampere  turns.  The  ampere  turns  are 
obtained  by  multiplying  the  number  of  turns  of  wire  in  coil,  by 
the  amperes  of  current  flowing  through  it. 

All  forms  of  matter  resist  the  development  of  magnetic  force. 
This  resistance  is  called  magnetic  reluctance.  The  reluctance  of 
air  is  much  greater  than  that  of  iron  or  steel,  but  is  constant; 
that  of  iron  and  steel  is  not.  If  one  thousand  ampere  turns 
develop  a  certain  magnetic  density  in  a  circuit  composed  wholly 
of  air,  two  thousand  ampere  turns  will  double  this  density.  In 
iron  and  steel  it  will  require  much  more  than  double  the  ampere 
turns  to  double  the  magnetic  density. 

If  in  a  magnetic  circuit  ten  inches  long,  100  ampere  turns 
develop  a  certain  density,  it  will  require  200  ampere  turns  to 
develop  the  same  density  if  the  magnetic  circuit  is  double  the 
length. 


HANDBOOK   ON    ENGINEERING.  47 


CHAPTER     V. 

SWITCH-BOARDS,    DISTRIBUTING    CIRCUITS    AND   SWITCH- 
BOARD INSTRUHENTS. 

Generators  of  the  constant  potential  type  are  made  so  as  to 
develop  a  certain  voltage  at  a  given  velocity,  but  in  some  cases  it 
is  not  practicable  to  run  them  at  the  exact  speed  for  which  they 
are  designed ;  and  in  others,  it  is  desired  to  vary  the  voltage 
slightly,  hence,  all  machines  are  provided  with  means  for  chang- 
ing the  e.m.f.  slightly.  This  regulating  device  is  also  necessary 
in  cases  where  the  load  is  for  a  time  light,  and  for  the  balance  of 
the  time  heavy ;  for,  as  we  have  shown,  the  voltage  will  vary  to 
some  extent  with  changes  in  the  strength  of  the  current.  If 
the  generator  is  at  some  distance  from  the  points  where  the  cur- 
rent is  used,  the  drop  of  voltage  in  the  lines  will  be  greater  with 
strong  currents  ;  hence,  when  the  load  is  heavy,  it  is  necessary  to 
increase  the  voltage  developed  by  the  generator.  As  it  is  not 
advisable  to  change  the  speed  of  the  engine,  the  variation  of  volt- 
age is  obtained  by  changing  the  strength  of  the  current  that 
flows  through  the  shunt  field  coils,  and  this  is  accomplished  by 
providing  a  resistance  that  can  be  cut  in  or  out  of  the  shunt  coil 
circuit,  as  is  illustrated  in  Fig.  68,  in  which  R  represents  the 
resistance,  or  field  regulator,  as  it  is  called.  When  the  lever  is 
moved  to  the  extreme  left  position,  all  the  regulator  resistance  is 
cut  out  of  the  circuit,  and  then  the  voltage  of  the  generator  is 
the  highest  that  can  be  obtained  with  the  speed  at  which  it  is  run- 
ning. When  the  lever  is  moved  to  the  extreme  right,  all  the 
resistance  of  the  regulator  is  introduced  into  the  shunt  coil  cir- 
cuit, and  then  the  voltage  is  the  lowest.  By  placing  the  lever  in 


48 


HANDBOOK    ON   ENGINEERING. 


intermediate  positions  between  the  extremes  right  an-d  left,  differ- 
ent voltages  may  be  obtained. 

To  be  able  to  operate  a  generator  furnishing  current  to  a  sys- 
tem of  distributing  wires,  it   is  necessary   to   have   a  number  of 


a, 


d 


R 


Fig.  08.    Resistance  regulator  for  shunt  coil. 

instruments  and  other  devices,  included  in  the  circuit,  some  of 
which  are  absolutely  indispensable,  and  others  of  which  are  simply 
conveniences,  and  may  be  looked  upon  as  luxuries.  The  various 
devices  required  are  shown  in  Fig.  69.  The  generator  is  shown 
at  M,  and  at  e  the  field  regulator  is  placed,  and  it  is  connected 
with  one  of  the  generator  armature  terminals  and  with  one  end 
of  the  shunt  coil  wires  by  means  of  wires  cif  d.  The  wires  c  c 
run  from  the  generator  terminals  to  the  voltmeter  F,  and  thus 
enable  us  to  see  what  the  voltage  is  at  all  times.  Wires  a  and  b 
convey  the  current  to  the  external  circuit,  with  which  they  can  be 
connected  or  disconnected  by  means  of  switches  ss  ss.  At  A  an 
ammeter  is  placed  which  indicates  the  strength  of  current  in 


HANDBOOK    ON    ENGINEERING. 


49 


amperes.  The  ammeter  can  be  placed  in  either  a  or  6,  as  the 
same  strength  current  flows  in  both.  At//  safety  fuses  are  pro- 
vided, so  as  to  open  the  circuit  in  case  the  current  becomes  so 
strong  as  to  be  capable  of  overheating  the  generator  wire.  If  one 
of  the  line  wires  runs  out  into  the  open  air,  and  is  carried  along  on 
poles,  we  will  have  to  provide  a  lightning  arrester,  as  shown  at  ft, 
this  being  connected  with  the  ground  as  at  g.  If  both  lines  run 
into  the  open  air,  an  arrester  must  be  placed  in  both ;  and  if 
both  are  confined  to  the  interior  of  a  building,  no  arresters  will 
be  required.  From  the  points  m  m  branch  circuits  may  be  run 
off  in  as  many  directions  as  necessary,  and  by  providing  switches 
s  s,  these  can  be  connected  or  disconnected  from  the  main  line 
when  desired. 

This  crude  arrangement  would  enable  us  to  operate  the  system 
successfully,  but  it  would  not  be  so  convenient  as  a  more  methodi- 


Fig.  69.    Instruments  required  in  the  circuit. 


cal  grouping  of  the  several  devices  and  instruments.  It  repre- 
sents the  way  things  were  done  in  the  early  days  of  electric  light- 
ing, but  at  the  present  time,  instead  of  having  the  several  parts 
scattered  about  in  a  helter-skelter  fashion,  they  are  all  assembled 

4 


50 


HANDBOOK    ON    ENGINEERING. 


upon  a  large  panel,  which  is  called  a  switch-board.  Fig.  70  give 
the  general  arrangement  of  wiring  and  location  of  devices  for  i 
simple  board  arranged  for  one  generator  feeding  into  five  externa 

\n      \P  


Fig.  70.    General  arrangement  of  switchboard. 


HANDBOOK    ON    ENGINEERING.  51 

cated  by  the  lines  n  _p,  //,  being  safety  fuses.  The  wires  i  i  con- 
vey the  main  current  from  the  generator  to  a  circuit  breaker  Z>, 
which  is  simply  a  switch  that  is  constructed  so  that  it  will  open 
automatically  when  the  current  becomes  too  strong.  From  the 
circuit  breaker,  the  current  passes  through  wires  a  and  b  to  the 
main  switch  F,  and  by  wire  c,  it  runs  from  here  to  the  ammeter 
A  and  from  the  latter  by  wire  c?  to  a  rod  1  which  is  called  a  bus 
bar.  The  upper  side  of  the  main  switch  is  connected  directly 
with  bus  2.  The  voltmeter  is  connected  with  two  busses  by  the 
wires  e  e.  The  field  regulator  is  located  back  of  the  board  at  J£, 
and  is  connected  in  the  shunt  coil  circuit  by  means  of  wires  h  h. 
The  switch  of  the  regulator  E  is  connected  with  a  hand-wheel  on 
the  front  of  the  switch-board,  so  that  the  attendant  can  watch 
the  voltmeter  as  he  turns  the  wheel  and  thus  see  just  what  affect 
the  movement  is  producing  on  the  voltage. 

In  addition  to  the  devices  shown  in  Fig.  70,  we  can,  if  desired, 
provide  a  recording  ammeter,  a  recording  voltmeter  and  a  watt- 
meter ;  the  first  two  would  give  us  a  record  of  the  amperes  and 
volts  for  a  certain  length  of  time,  generally  24  hours,  and  the 
last  one  would  register  the  amount  of  electrical  energy.  We 
could  also  provide  ammeters  for  each  one  of  the  distributing  cir- 
cuits, so  as  to  know  the  strength  of  current  in  each  one. 

If  we  desire  to  arrange  the  switch-board  for  two  generators, 
and  these  are  of  the  shunt  type,  we  will  require  no  changes  in 
Fig.  70,  except  to  provide  another  regulator  and  a  main  switch 
and  circuit  breaker  for  the  additional  machine.  This  arrange- 
ment of  board  is  suitable  for  a  single  compound  wound  generator", 
or  any  number  of  shunt  wound  machines,  but  if  we  have  two  or 
more  compound  generators,  the  connections  between  these  and 
the  bus  bars  will  have  to  be  somewhat  modified. 

The  modifications  required  in  a  switch-board  for  two  or  more 
compound  generators  can  be  made  clear  by  the  aid  of  Figs.  71 
and  72,  In  the  first  figure,  we  can  see  that  if  the  current  return- 


52 


HANDBOOK    ON    ENGINEERING. 


ing  from  the  main  line  through  n  divides  into  wires  a  and  6,  it 
will  remain  divided  until  it  passes  through  the  armatures  and  the 
F  coils  of  the  two  machines,  and  thence  through  wires  e  e,  it  will 


Fig.  71.    Connections  from  machines  to  switchboard. 


reunite  again  in  wire  p.  In  Fig.  72,  the  two  parts  of  the  current 
will  flow  through  wires  d  d  to  the  single  wire  e,  and  then  divide 
into  wires//,  and  thus  reach  the  coils  F  F,  and,  finally,  through 
wires  h  7i,  reach  p.  In  Fig.  71,  if  the  right  side  armature  gen- 
erates more  current  than  the  other  one,  the  F  coil  of  that  gener- 
ator will  be  traversed  by  the  strongest  current,  for  in  each  machine 
the  strength  of  current  in  the  armature  and  the  F  coil  will  be 
nearly  the  same.  Now,  if  the  right  side  machine  generates  the 
strongest  current,  it  is  because  its  voltage  is  the  highest,  but  the 
fact  that  its  F  coil  will  be  traversed  by  the  strongest  current  will 
make  its  voltage  still  higher,  thus  increasing  the  difficulty.  In 
Fig.  72,  the  current  flowing  through  the  two  F  coils  will  be  the 
same,  no  matter  how  much  the  two  armature  currents  may  differ, 


HANDBOOK    ON    ENGINEERING. 


53 


for  these  come  together  in  wire  e,  and  passing  from  this  to  the  two 
F  coils,  the  current  will  divide  in  equal  amounts.  As  can  be 
seen,  the  effect  of  adding  the  wires  d  d,  e  and //in  Fig.  72  is  to 
equalize  the  currents  that  flow  through  the  F  coils,  and  thus  pre- 
vent, as  far  as  possible,  the  unequal  action  of  the  generators. 

When  two  or  more  compound  generators  are  connected  so 
as  to  feed  into  the  same  general  circuit,  the  connections  are 
made  in  accordance  with  Fig.  72.  Fig.  73  illustrates  a  switch- 
board for  two  compound  generators,  and,  as  will  be  noticed,  the 
most  striking  difference  between  it  and  Fig.  70,  is  that  there 
are  three  bus  bars  instead  of  two.  One  of  these  busses  is 
called  the  equalizer,  and  it  takes  the  place  of  wires  d  d  e  and 


Fig.  72.    Arrangement  of  equalizing  connections. 

//in  Fig.  72.  The  equalizing  connections  run  from  generator 
wires/  to  the  main  switches  S,  and  thence  to  bus  1.  The  h  wires 
of  the  generators  run  to  one  side  of  the  circuit  breakers  D  E, 


54 


HANDBOOK    ON    ENGINEERING. 


and  thence  to  the  middle  blades  of  the  S  switches,  and  from  these 
to  the  bus  2.     The  generator  wires  run  to  the  outside   blades  o: 

• 


ff 


Fig.  73.    Switchboard  for  two  compound  generators. 

the  circuit  breakers,  and  from  these  to  the  ammeters  A  A,  anc 
thence  to  bus  3.  The  voltmeters  are  connected  with  wires  k  am 
/,  and  thus  indicate  the  e.m.f.'s  of  the  generators. 


HANDBOOK    ON    ENGINEERING.  55 

If  another  generator  were  added,  it  would  be  connected  with 
the  bus  bars  in  the  same  way. 

In  starting  two  or  more  compound- wound  generators,  one 
machine  is  started  first,  and  then  the  second  is  run  up  to  full 
speed,  and  its  voltage  is  adjusted  by  means  of  the  regulator  R,  so 
as  to  be  the  same  as  that  of  the  machine  that  is  running.  When 
the  voltages  of  the  two  machines  are  equal,  the  main  switch  of 
the  second  machine  is  closed  so  as  to  connect  it  with  the  bus  bars. 
This  action  will  generally  make  a  slight  change  in  the  voltage  of 
the  second  machine,  causing  it  to  run  up  or  down  a  trifle ;  and  as 
a  result  by  looking  at  the  ammeters,  we  will  find  that  it  is  taking 
more  or  less  than  its  share  of  the  load.  If  such  is  the  case,  we 
manipulate  the  regulator  R,  until  the  loads  are  properly  divided. 
Whether  the  voltage  of  the  second  machine  will  rise  or  fall  after 
it  is  connected  with  the  bus  bars,  will  depend  upon  the  extent  to 
which  it  is  compounded  ;  if  slightly  compounded,  the  voltage  will 
drop,  and  if  heavily  compounded,  it  will  rise. 

The  switch-boards  illustrated  are  adapted  to  what  is  called  the 
two- wire  system  of  distribution,  but  in  cases  where  it  is  desired 
to  transmit  the  current  to  a  considerable  distance,  without  using 
extra  large  wire,  the  three-wire  system  of  distribution  is 
employed.  This  system  is  illustrated  in  Figs.  74  to  76. 

Suppose  we  have  two  generators  as  indicated  at  G  O  in  these 
diagrams,  and  let  the  direction  of  the  current  through  both  be 
from  bottom  toward  the  top ;  then  it  is  evident,  that  if  we  remove 
the  middle  wire  0,  the  lower  machine  will  deliver  current  into  the 
upper  one,  and  if  each  generator  develops  an  e.m.f.  of  115  volts, 
the  combined  e.m.f.  will  be  230  volts,  and  this  will  be  the 
pressure  between  the  bottom  and  top  wires ;  but  the  voltage 
between  either  wire  and  the  center  one  will  only  be  115.  Suppose 
we  have  a  number  of  lamps  connected  between  wire  P  and  the 
center  wire  0,  and  an  equal  number  of  lamps  between  0  and  N, 
as  \s  shown  in  Fig.  74  ;  then  it  is  evident  that  the  same  amount 


HANDBOOK    ON    ENGINEERING. 


of  current  will  flow  through  both  sets,  arid  as  a  consequence,  a 
the  current  that  passes  from  the  upper  generator  into  wire  P  wi 
go  directly  through  both  sets  of  lamps  to  the  lower  wire  N,  an 
thus  return  to  the  lower  side  of  the  bottom  generator.  Und< 


Arrangements  of  three- wire  system. 

these  conditions,  the  lamps  will  be  acted  upon  by  115  volts  eact 
but  the  current  will  be  driven  through  the  circuit  by  a  voltage  c 
230.  Now,  if  the  voltage  is  doubled,  four  times  the  number  c 
lamps  can  be  supplied  with  the  same  size  wires ;  hence,  the  cos 
of  line  wire  per  lamp  will  be  reduced  to  one-fourth.  Suppose 
that  instead  of  having  the  lamps  equally  divided  as  in  Fig.  14 


HANDBOOK   ON    ENGINEERING.  57 

they  are  arranged  as  in  Fig.  75  ;  then  since  the  current  fed  into 
the  system  from  the  upper  wire  P  is  only  sufficient  for  five  lamps, 
while  there  are  seven  lamps  in  the  lower  section,  it  follows  that 
through  wire  0  a  current  sufficient  for  two  lamps  must  be  sup- 
plied. The  way  in  which  the  currents  would  flow  in  this  case  is 
clearly  indicated  by  the  arrows. 

In  Fig*  74,  it  will  be  seen  that  if  we  removed  the  middle  wire, 
the  lamps  would  not  be  affected,  for  none  of  the  current  comes 
through  it;  but  in  Fig.  75,  if  we  cut  the  middle  wire,  two  of  the 
lower  lamps  would  be  unprovided  for.  From  this  it  will  be  seen 
that  the  object  of  the  middle  wire  is  simply  to  provide  the  extra 
current  required  for  the  side  that  carries  the  largest  number  of 
lamps.  If  the  lights  are  so  arranged  that  on  both  sides  of  the 
central  wire  0  the  number  is  practically  the  same  at  all  times, 
the  center  wire  can  be  made  very  small,  but  such  perfect  balance 
cannot  be  obtained  always,  and  on  that  accouut,  the  center,  or 
neutral  wire,  as  it  is  called,  is  made  of  the  same  size  as  the 
others,  except  in  large  systems,  in  which  it  is  sometimes  not  more 
than  one-third  the  size. 

As  motors  require  large  amounts  of  current,  they  are  nearly 
always  made  to  operate  with  a  voltage  of  230,  and  are  connected 
with  the  outside  wires  of  the  system,  as  is  shown  in  Fig.  76,  in 
which  a  a  a  a  and  c  c  c  c  indicate  lamps  connected  between  the 
sides  and  the  neutral  wire,  and  ABC  are  motors  connected 
across  the  outside  lines. 

When  a  switch-board  is  arranged  for  two  generators  connected 
with  a  three-wire  system,  we  use  three  bus  bars,  just  as  in  Fig. 
70,  but  discard  the  equalizing  connection,  and  connect  the 
generators  with  the  busses  in  the  same  way  as  they  are  connected 
with  wires  N  0  and  P  in  Figs.  74  to  76.  If  we  have  a  number  of 
generators  feeding  into  the  three- wire  system,  then  we  connect 
each  set  with  an  equalizer  bus;  that  is,  provide  two  sets  of 
busses,  and  the  P  and  N  busses  of  these  two  sets  we  connect 


58 


HANDBOOK    ON    ENGINEERING. 


with  a  third   set  in  the  proper  order  for  the  three-wire   system, 
and  from  the  latter  busses  the  external  circuits  are  fed. 

If  we  desire  to  supply  a  larger  building  with  a  lighting  and 
power  system,  we  can  run  the  wires  in  almost  any  way,  providing 
we  make  connections  with  the  lamps  and  motors,  but  if  we  adopt 


Fig.  77.    Light  and  power  system  for  building. 

a  systematic  arrangement  it  will  require  less  labor  to  operate  the 
plant,  and  when  anything  goes  wrong  we  will  be  able  to  locate 
the  difficulty  with  much  less  trouble  and  in  less  time.  The  best 
way  to  accomplish  this  is  by  the  use  of  small  switch-boards 
located  at  different  points  in  the  building,  these  becoming  centers 


HANDBOOK    ON    ENGINEERING.  f)9 

of  distribution,  from  which  all  the  lamps  are  supplied.  The 
general  arrangement  of  such  a  system  dan  be  understood  from 
Fig.  77,  in  which  B  represents  the  main  switch-board,  located  in 
the  engine  room,  and  e  e  e  the  several  floors  upon  which  the  lights 
are  located.  From  the  main  switch-board  we  run  up  four  lines, 
one  to  each  floor,  and  locate  secondary  boards  at  C  C  and  D  DD. 
We  can  also  run  out  lines  directly  from  the  board  to  the  lamp 
circuits  as  at  c  c  c  c.  From  the  boards  C  (7,  we  run  circuits  to 
smaller  boards,  as  shown  at  J5J,  F,  A,  A,  A,  and  b  b  b.  From 
each  one  of  these  small  boards  we  can  run  out  circuits  to  the 
lamps. 

These  small  switch-boards  are  called  panel  boards  or  boxes, 
and  also  distribution  boards.  They  are  made  of  all  sizes  from 
eight  or  ten  inches  square,  up  to  four  or  five  feet,  and  are 
arranged  to  feed  into  one  or  two,  or  fifty  or  sixty  circuits, 
supplying  anywhere  from  five  or  six  lights  up  to  a  thousand  or 
more. 

The  construction  of  distribution  boards  can  be  understood 
from  Figs.  78  and  79,  the  first  being  arranged  for  the  three- 
wire  system,  and  the  second  for  the  two- wire.  Fig.  78  is  ar- 
ranged to  feed  ten  circuits,  and  is  provided  with  one  main  switch 
by  means  of  which  the  entire  box  can  be  disconnected  from  the 
main  line.  The  distributing  circuits  are  provided  with  proper 
safety  fuses  on  the  outside  wires,  so  that  if  anything  goes  wrong 
and  the  current  increases  to  a  dangerous  point,  the  circuit  will  be 
open.  No  fuse  is  placed  on  the  middle  wire,  as  it  is  not  neces- 
sary, and  might  result  in  cutting  out  both  sides  of  the  circuit 
when  only  one  was  disabled. 

Fig*  79  is  a  mor'e  complete  panel,  because  each  one  of  the  six 
distribution  circuits  is  provided  with  a  switch,  so  that  it  is  pos- 
sible to  disconnect  any  of  the  circuits  without  interfering  with  the 
others.  In  some  cases  a  distribution  board  of  this  kind  is  the 
only  thing  that  will  answer  the  purpose,  but  in  others,  the  more 


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HANDBOOK    ON    ENGINEERING. 


simple  construction  of  Fig.  78  answers  just  as  well.  The  fuses 
in  Fig  78  are  shown  at  E  F.  These  fuses  are  sometimes  made  so 
that  they  can  be  used  as  switches  ;  that  is.  they  can  be  pulled  out 


Fig.  78.    Board  for  three-wire  system. 

Fig.  79.    Board  for  two-wire  system. 

of  place  and  thus  open  the  circuit,  and  if  one  blows  out  it  can  be 
removed  and  a  new  fuse  be  put  in,  and  then  it  can  be  replaced, 
thus  placing  the  disabled  circuit  in  service  without  interfering 
with  the  others. 

The  ammeters  and  voltmeters  used  on  switch-boards  depend 
for  their  operation  upon  the  repulsion  between  magnetic  lines  of 
force.  A  great  many  different  constructions  are  used,  but  most 
of  them  operate  upon  the  principles  illustrated  in  Fig.  80  or  81. 
If  a  small  bar  of  iron  c  is  placed  between  the  poles  of  a  permanent 
magnet,  as  in  Fig.  80,  it  will  be  held  in  the  horizontal  position  by 
the  attraction  of  the  magnet.  If  it  is  surrounded  by  a  stationary 
coil  of  wire  &?  through  which  a  current  of  electricity  passes,  then 


HANDBOOK    ON   ENGINEERING.  61 

it  will  be  under  the  influence  of  two  forces,  one  the  attraction  of 
the  poles  N  S  of  the  magnet,  and  the  other  the  attraction  of  the 
lines  of  foice  developed  by  the  current  flowing  through  coil  b. 
The  action  of  the  latter  will  tend  to  swing  the  rod  c  into  the  ver- 
tical position .  The  force  of  the  magnet  will  remain  constant,  but 
the  force  of  the  coil  will  vary  with  the  strength  of  the  current 
passing  through  it ;  hence,  the  stronger  the  current  the  more  the 
bar  c  will  be  swung  around  into  the  vertical  position.  If  we  pro- 
vide a  small  counter- weight,  as  shown  in  the  illustration,  to  resist 
the  action  of  the  coil,  we  will  have  a  means  that  will  enable  us  to 
adjust  the  movement  of  the  bar,  so  that  it  will  swing  around 
through  a  given  angle  for  a  given  increase  in  current.  If  a 
pointer  a  is  secured  to  c  it  will  swing  over  the  scale  as  shown, 
when  c  is  rotated  by  the  action  of  the  coil. 

If  coil  b  is  mounted  so  that  it  may  swing  around  the  center 
pivot,  we  can  discard  bar  c,  for  then  as  soon  as  a  current  traverses 
&,  the  lines  of  force  developed  around  it  will  be  attracted  by 


Figs.  80  and  81.  Principles  of  ammeter  and  voltmeter. 

those  of  the  permanent  magnet,  and  will  exert  a  twisting  force  so 
as  to  place  the  axis  of  the  coil  parallel  with  the  lines  of  force 
passing  from  N  to  S.  In  this  case  as  in  the  previous  case,  the 


6B  HANDBOOK    ON    ENGINEERING. 

effort  to  twist  b  around  will  be  proportional  to  the  strength  of 
the  current,  hence,  the  stronger  the  current  the  greater  the 
swing.  Ammeters  and  voltmeters  are  made  on  these  principles, 
and  the  only  difference  in  the  two  instruments  is  in  the  size  of 
the  wire  used  for  the  coils. 

Figs*  82  and  83  illustrate  the  principle  upon  which  circuit 
breakers  are  made.  In  Fig.  82,  suppose  a  current  flows  through 
magnet  2£,  then  it  will  attract  the  lever  A,  the  latter  being  made 


Figs.  82  and  83.    Principles  of  circuit  breakers. 

of  iron.  If  the  current  is  weak  it  may  not  develop  a  sufficient 
attractive  force  in  E  to  lift  the  weight  D,  and  in  that  case  A  will 
remain  where  it  is.  If,  however,  the  current  is  increased  until  E 
becomes  strong  enough  to  lift  Z>,  then  A  will  move  over  toward 
the  magnet,  and  the  catch  "  a  "  falling  behind  it,  will  not  allow 
it  to  return  to  its  former  position  until  placed  there  by  hand. 
When  A  swings  over,  it  carries  J5,  and  thus  breaks  the  connec- 
tion with  C  and  opens  the  circuit.  Thus  it  will  be  seen  that  by 
properly  adjusting  the  weight  D  and  the  magnet  E,  we  can  set  the 
device  so  as  to  open  the  circuit  whenever  the  current  reaches  a 
certain  strength.  This  is  the  principle  upon  which  circuit  break- 


HANDBOOK   ON    ENGINEERING.  63 

•*rs  act,  but  such  a  device  as  Fig.  82  would  be  of  no  service  for 
lighting  circuits,  because  the  distance  by  which  0  and  B  are 
separated  is  too  small  to  break  the  current.  By  modifying  the 
construction  as  in  Fig.  83,  we  can  obtain  a  device  that  will  give  a 
wide  separation  at  the  breaking  point.  In  this  construction ,  the 
lever  A  when  drawn  towards  the  magnet,  strikes  the  catch  a,  so 
as  to  release  lever  .B,  and  then  the  weight  D  throws  the  latter 
down  to  the  position  shown  in  broken  lines,  thus  giving  a  wide 
separation  between  F  and  (7.  By  moving  the  weight  on  the  lower 
arm  at  A,  the  device  can  be  adjusted  so  as  to  act  with  different 
strengths  of  current. 

Circuit  breakers  as  actually  constructed,  do  not  have  the 
appearance  of  this  diagram,  but  they  operate  on  the  principle 
illustrated  by  it. 

The  electromotive  force  in  volts  developed  in  the  armature  of 
a  motor,  or  generator,  can  be  determined  if  we  know  the  number 
of  wires  upon  the  outer  surface,  the  number  of  maxwells  of  mag- 
netic flux  that  pass  through  the  armature,  and  the  revolutions  per 
second.  The  rule  for  the  calculation  is  as  follows :  — 

Multiply  the  number  of  wires  on  the  outer  surface  of  the  arma- 
ture by  the  maxwells  of  magnetic  flux  and  by  the  revolutions  per 
second,  and  divide  this  product  by  100,000,000. 

This  is  the  rule  for  two  pole  armatures.  For  multipolar  arma- 
tures with  series,  or  wave  winding,  use  same  rule  making  the 
flux  equal  to  the  sum  of  the  fluxes  issuing  from  all  the  positive  poles. 

For  multipolar  armatures  with  a  lap,  or  parallel  winding,  use 
same  rule  but  take  the  flux  issuing  from  one  pole  only. 

To  obtain  the  pull  in  pounds  of  a  motor  armature  at  one  foot 
radius  use  the  following  rule :  — 

Multiply  the  number  of  wires  on  the  outer  surface  of  armature 
by  the  amperes  of  armature  current,  and  by  total  number  of  max- 
wells of  magnetic  flux  passing  through  armature,  and  divide  this 
product  by  852,000,000.  See  pages  13  and  46. 


64  HANDBOOK    ON    ENGINEERING. 


' 

CHAPTER     VI. 

ELECTRIC  MOTORS. 

' 

Motors  are  made  so  as  to  run  at  a  constant  velocity,  or  for 
variable  speed.  For  the  latter  type  of  machine,  the  field  coils  are 
wound  in  series,  and  for  constant  speed  the  shunt  winding  is  used. 
A  motor  of  either  kind  cannot  be  started  successfully  without 
placing  an  external  resistance  in  the  armature  circuit,  because, 
when  the  armature  is  at  a  standstill,  there  is  nothing  but  the 
resistance  of  the  wire  to  hold  the  current  back,  and  as  a  result,  if 
no  extra  resistance  is  provided,  the  first  rush  of  current  would  be 
very  great.  As  soon  as  the  armature  begins  to  revolve,  an  e.m.f . 
is  induced  in  its  wires,  and  this  acts  in  opposition  to  the  e.m.f. 
of  the  line  current ;  that  is,  it  acts  like  a  back  pressure,  and  holds 
the  current  back.  On  this  account,  the  e.m.f.  of  a  motor  is 
called  a  counter  e.m.f.,  and  it  is  abbreviated  into  c. e.m.f. 

The  way  in  which  the  external  resistance  is  connected  with 
a  motor  is  illustrated  in  Fig.  84,  in  which  M  is  the  motor  and 
R  the  external  resistance.  D  is  a  main  switch,  by  means  of 
which  the  motor  is  connected  with  the  main  line.  This  switch  is 
closed  first,  and  then  switch  F  is  moved  to  the  right  until  it  cov- 
ers the  first  contact  of  the  resistance  R.  The  current  can  then 
pass  directly  to  the  field  shunt  coils  through  wire  e,  and  thence  by 
wire  a,  return  to  the  main  line.  The  armature  current,  however, 
has  to  first  pass  through  the  resistance  R,  before  it  can  reach  wire 
i,  and  thus  the  armature.  As  soon  as  the  armature  begins  to 
speed  up,  the  switch  F  is  advanced,  step  by  step,  and  in  a  few 
seconds  it  is  moved  to  the  extreme  right  position,  in  which  all  the 
resistance  R  is  cut  out  of  the  armature  circuit.  When  F  reaches 
this  position,  the  motor  should  be  running  at  full  speed. 


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65 


If  the  current  should  stop  while  the  motor  is  running,  the 
machine  would  stop,  also,  and  then,  if  the  current  were  turned 
on  again,  the  motor  would  be  caught  with  the  armature  connected 
across  the  line  without  an  external  resistance,  and  as  it  would  be 
at  a  standstill,  the  current  would  rise  to  an  enormous  strength. 
To  prevent  this,  the  switch  F  is  always  opened  whenever  the  motor 
stops.  The  attendant  may  forget  to  do  this,  however;  therefore 
automatic  switches  have  been  devised  that  will  open  themselves 
whenever  the  current  dies  out. 


Fig.  84.    External  resistance  connected  with  motor. 

A  simple  switch  provided  with  a  resistance  so  as  to  be  suited 
to  start  a  motor,  is  called  a  motor-starter,  and  one  that  in  addi- 
tion is  provided  with  means  for  automatically  flying  to  the  open 
position  whenever  the  current  fails,  is  called  an  automatic  under- 
load starter. 

If  the  motor  is  very  much  overloaded,  its  speed  will  slow  down 
and  the  current  will  increase  in  strength.  If  the  overload  is  suf- 
ficient, the  current  will  become  so  strong  as  to  be  able  to  burn  out 


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HANDBOOK    ON    ENGINEERING. 


the  armature ;  hence,  it  is  desirable  to  provide  a  circuit  breaker 
that  will  open  the  circuit  when  the  current  becomes  so  strong  as 
to  be  liable  to  burn  out  the  machine.  Motor-starters  are  made 
with  a  circuit-breaking  attachment,  and  are  then  called  automatic 
overload  motor-starters.  A  device  that  combines  the  under  and 
overload  starter,  features  is  called  an  automatic  under  and  over- 
load starter,  and  by  some  people  it  is  called -a  u  no  voltage  "  and 
"  overload  starter." 

When  motors  were  first  introduced,  a  great  deal  of  trouble 
was  experienced  with  the  starters,  owing  to  the  fact  that  they 
were  arranged  so  that  when  the  motor  was  stopped,  the  connection 
with  the  field  coils  was  broken.  Now,  the  current  flowing  through 
the  field  coils  objects  to  stop  flowing  when  the  connection  is 
broken,  and,  consequently,  it  continues  to  flow  between  the  end  of 
switch  F  in  Fig.  84,  and  the  last  of  the  contacts  of  R,  until  the 
distance  is  more  than  the  e.m.f.  of  the  current  can  overcome. 


Principle  of  motor  starter. 


This  action  produces  serious  sparking  at  the  last  terminal,  and  in 
addition,  produces   a    severe  strain   upon  the   insulation  of  the 


HANDBOOK    ON    ENGINEERING.  07 

field  coils,  because,  as  the  current  is  headed  off  in  one  direction, 
it   tries  to  find    an    outlet   in    another.     This  action  is  what  is 


Fig.  86.    Another  style  of  motor  starter. 

commonly  called  the  "kick  of  the  motor  field."  All  this 
trouble  can  be  obviated  by  connecting  the  starter  with  the  motor 
in  such  a  way  that  the  field  circuit  is  never  opened,  as  is  shown 
in  Fig.  84.  As  this  is  quite  an  important  device  it  is  presented 
in  a  more  simple  form  in  Fig.  85,  in  which  it  will  be  seen  that 
the  field  coils  and  armature  are  permanently  connected,  so  that 
when  switch  S  opens  the  circuit,  the  field  current  can  flow  through 
the  armature,  until  it  dies  out.  All  first-class  concerns  make 
motor  starters  with  this  connection,  at  the  present  time.  Some 
of  them  add  the  curved  contact  e.  Without  this  contact,  it  can 
be  seen  that  when  the  switch  S  is  moved  to  the  top  position,  the 


68  HANDBOOK    ON    ENGINEERING. 

resistance  R  is  simply  transferred  from  the  armature  to  the  field 
circuit,  and  that  the  current  going  to  the  field  coils  has  to  pass 
through  this  resistance.  As  this  resistance  is  insignificant  in 
comparison  with  that  of  the  shunt  coils,  it  makes  little  difference 
whether  it  is  left  in  the  field  circuit  or  not,  but  by  the  addition  of 
e  it  can  be  cut  out. 

Variable  speed  motors  are  always  arranged  so  that  the  speed 
may  be  changed  by  hand  as  conditions  may  require.  Trolley-car 
motors  are  of  this  type,  and  so  are  the  motors  used  for  printing 
presses,  and  many  other  kinds  of  work.  Figs.  86  to  88  show 
arrangements  by  means  of  which  the  speed  may  be  varied  with 
series  wound  motors.  In  Fig.  86,  E  is  the  starting  box  and  F  is 
the  speed  regulator.  In  the  act  of  starting,  the  switches  are  in 
the  position  shown.  To  start,  the  switch  S  and  E  is  turned  so 
as  to  close  the  circuit  with  the  resistance  R  all  included.  S  is 
moved  toward  the  left  as  the  armature  speeds  up,  and  reaches 
the  last  position  when  full  speed  is  attained.  If  the  switch  of  F 
is  now  closed,  a  portion  of  the  current  will  be  diverted  from  the 
armature,  and  thus  its  rotating  force  will  be  reduced,  and  thereby 
its  speed.  This  method  of  speed  control  is  also  arranged  so 
that  the  two  switches  act  together,  so  as  to  introduce  resistance 
into  the  motor  circuit,  and  at  the  same  time  divert  more  or  less 
of  the  current  around  the  armature.  It  is  not  used  extensively, 
as  all  the  current  that  passes  through  F  is  just  so  much  thrown 
away. 

In  Fig.  87  the  speed  is  controlled  by  means  of  the  switch  F, 
which  cuts  out  portions  of  the  field  coils  and  this  changes  the 
strength  of  the  field.  With  this  arrangement,  if  a  portion  of 
the  field  is  cut  out,  the  motor  will  run  faster,  because  the  c.e.m.f 
will  be  reduced,  therefore,  the  armature  current  will  be  increased. 
To  obtain  a  wide  range  of  regulation,  it  is  necessary  to  wind  a 
large  number  of  turns  of  wire  on  the  field,  so  that  with  all  the 
wire  in  service,  the  speed  may  be  the  lowest  required. 


HANDBOOK    ON    ENGINEERING. 


69 


Fig.  88  shows  another  arrangement  that  varies  the  strength  of 
the  field  by  diverting  a  portion  of  the  current  through  switch  F. 
It  gives  as  wide  a  range  of  regulation  as  Fig.  87,  but  is  not  so 
economical. 

Figs-  86  and  88  cannot  be  used  to  regulate  the  speed  of  shunt 
motors,  but  Fig.  87  can.  The  first  two  named  figures,  if  used 


Fig.  87.    Regulator  for  shunt  motor. 

with  a  shunt  motor,  would  simply  afford  a  third  path  through 
which  current  could  pass  from  one  side  of  line  to  the  other,  that 
is,  from  the  p  to  the  n  wires,  but  this  would  not  materially  affect 
the  strength  of  current  that  would  flow  through  the  armature  and 
field  coils.  They  work  with  series  wound  motors,  because  the 
current  is  not  shunted  from  wire  p  to  wire  n  but  simply  from 
one  side  of  the  armature,  or  the  field,  to  the  other. 


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HANDBOOK    ON    ENGINEERING. 


Fig*  89  shows    an  arrangement   by  means    of  which   a    shunt 
motor  can  be  made  for  variable  speed.     In  this   case,   the  switch 


Fig*  88.    Device  for  varying  strength  of  field. 

and  resistance  E  is  simply  an  ordinary  starter,  and  F  is  a  resist- 
ance that  is  introduced  in  the  field  circuit,  so  as  to  vary  the 
strength  of  the  field.  With  this  arrangement  the  slowest  speed  is 
obtained  when  all  the  resistance  of  F  is  out  of  the  circuit. 

The  direction  in  which  a  motor  runs  can  be  reversed  by  sim- 
ply reversing" the  direction  of  the  current  through  the  armature. 
Any  of  the  arrangements  for  varying  the  speed  can  be  used  in 
connection  with  reversible  motors  by  arranging  the  switch  so  as 


HANDBOOK    ON    ENGINEERING. 


71 


to  reverse  the  armature  connections.  Fig.  90  will  give  a  fair 
idea  of  the  way  in  which  a  reversing  switch  is  made.  This  repre- 
sents the  type  of  switch  used  most  generally  for  this  purpose,  and 
it  is  known  as  the  cylinder  switch.  It  is  the  kind  used  on  trol- 
ley-cars. The  vertical  row  of  circles  numbered  from  one  to 
eleven  represents  stationary  contact  pieces,  to  which  the  terminals 
of  the  motor,  the  line  and  the  resistance  are  attached.  The 
shaded  parts  B  B  are  metal  plates  that  are  secured  to  the 
surface  of  a  cylinder,  that  is  so  located  that  as  it  is  turned  in  one 
direction  or  the  other,  these  plates  slide  over  the  stationary  con- 
tacts. If  the  cylinder  is  turned  so  that  the  plates  on  the  right 
side  slide  over  the  contacts,  the  motor  will  run  in  one  direction, 
and  if  the  cylinder  is  turned  in  the  other  direction,  the  motor  will 
be  reversed.  Suppose  the  right  side  plates  slide  over  the  con- 


Fig.  89.    Device  for  varying  speed  of  shunt  motor. 


tacts,  then  the  current  from^>  will  pass  to  contact  2,  and  thence 
to  wire  a,  and  to  the  left-side  of  the  field.  Through  wire  d  it 
will  return  from  the  field  to  contact  5,  and  by  means  of 


T2, 


HANDBOOK    ON    ENGINEERING. 


plates  N  and  T,  which  are  connected  as  shown  at  JX1,  it  will  reach 
contact  3  and  wire  fr,  which  runs  to  the  lower  side  of  the  arma- 
ture. From  the  top  of  the  armature,  through  wire  c,  the  current 
will  return  to  contact  4  and  through  plates  S  and  M  and  the  con- 
nection X  will  reach  contact  6 ,  which  by  one  of  the  wires  e  con- 


Fig.  90.    Principle  of  reversing  device. 


nects  with  the  left-side  of  the  resistance  U.  From  the  right-side 
of  this  resistance,  the  current  will  pass  to  contact  10,  and  thus 
to  contact  11,  through  the  cylinder  plate,  and  in  that  way  reach 
line  wire  n. 

If  the  cylinder  is  turned  further  around,  contact  7  will  be  cov- 
ered by  plate  M ,  and  this  will  cut  one  section  of  D.     By  a  further 


HANDBOOK    ON    ENGINEERING.  73 

movement,  contact  8  will  be  covered,  thus  cutting  out  another 
section,  and  by  continuing  the  movement,  all  of  D  can  be  cut  out. 

If  the  cylinder  is  turned  so  as  to  slide  the  left-side  plates  over 
the  contacts,  the  change  effected  will  be  that  contact  5  will  be 
connected  with  4  instead  of  with  3,  and  contact  6  will  be  con- 
nected with  3  instead  of  4,  thus  reversing  the  direction  of  the 
current  through  the  armature. 

The  strength  of  an  electric  current  is  measured  in  amperes. 
The  electromotive  force  that  drives  an  electric  current  through  a 
circuit  is  measured  in  volts.  The  resistance  that  a  wire  or  other 
circuit  offers  to  the  passage  of  an  electric  current  through  it  is 
measured  in  ohms. 

The  unit  of  resistance,  the  ohm,  is  the  resistance  of  a  column 
of  mercury  about  40  inches  long  and  about  five  hundredths  of  an 
inch  in  diameter,  or,  to  be  more  exact,  106  centimeters  long,  and 
one  millimeter  in  diameter. 

THE  WATT. 

The  watt  is  the  unit  of  electric  power  —  the  volt-ampere,  the 
power  developed,  and  is  equal  to  TJ^  of  one  horse  power.  A  con- 
venient multiple  of  this  is  called  the  Kilowatt,  written  K.  W.,  and 
is  equal  to  1,000  watts. 

THE  AHPERE. 

The  ampere  is  the  practical  unit  of  electric  current,  such  a  cur- 
rent [or  rate  of  flow,  or  transmission  of  electricity]  as  would 
pass,  with  an  electromotive  force  of  one  volt,  through  a  circuit 
whose  resistance  is  equal  to  one  ohm  ;  a  current  of  such  a  strength 
as  would  deposit  from  solution  .006084  grains  of  copper  per 

second. 

CANDLE  POWER. 

The  candle  power  is  the  unit  of  light ;  and  a  standard  candle 
is  a  candle  of  definite  composition  which  with  a  given  consump- 
tion in  a  given  time,  will  produce  a  light  of  a  fixed  and  definite 
brightness.  A  candle  which  burns  120  grains  of  spermaceti  wax 
per  hour,  or  two  grains  per  minute,  will  give  an  illumination 
equal  to  one  standard  candle. 


74  HANDBOOK    ON    ENGINEERING. 


CHAPTER    VII. 

INSTRUCTIONS  FOR  INSTALLING  AND  OPERATING  SLOW  AND 
MODERATE  SPEED  GENERATORS  AND  HOTORs! 

To  remove  the  armature,  take  off  the  brush-holders,  brush 
yoke,  pulley  and  bearing  caps  and  put  a  sling  on  the  armature,  as 
shown  in  accompanying  illustration.  A  spreader  of  suitable 
length  should  be  used  and  its  location  adjusted  to  prevent  the 
rope  from  drawing  against  the  flange  or  end  connections. 

In  assembling,  marked  parts  of  the  machine  should  be  assem- 
bled strictly  according  to  the  marking.  Clean  all  connection 
joints  carefully  before  clamping  them  together.  Wipe  the  shaft- 
bearing  sleeves  and  oil  cellars  perfectly  clean  and  free  from  grit. 
Place  the  bearing  sleeves  and  oil  rings  in  position  on  the  shaft 
and  then  lower  the  armature  into  place,  taking  care  that  the  oil 
rings  are  not  jammed  or  sprung.  As  soon  as  the  armature  is  in 
position,  pour  a  little  oil  in  the  bearing  sleeves,  put  the  caps  on 
the  boxes  and  screw  them  down  snugly.  The  top  field  should 
next  be  put  on  and  bolted  firmly  into  position,  and  a  level  placed 
on  the  shaft  to  check  the  leveling  of  the  foundation. 

Fill  the  bearings  with  the  best  grade  of  thin  lubricating  oil  and 
do  not  allow  it  to  overflow.  Oil  throwing  is  usually  due  to  an 
excess  of  oil  and  can  be  avoided  by  care  in  filling  the  oil  cellars. 

To  complete  the  assembly,  place  the  pulley  on  the  shaft,  draw 
up  the  set  screws  and  put  on  the  brush  rigging  and  connection 
blocks. 

STARTING. 

Before  putting  on  the  belt,  see  that  all  screws  and  nuts  are 
tight  and  turn  the  armature  by  hand  to  see  that  it  is  free  and 


HANDBOOK   ON   ENGINEERING. 


75 


does  not  rub  or  bind  at  any  point.  Put  on  the  belt  with  the 
machine  so  placed  on  the  rails  as  to  have  the  minimum  distance 
between  pulley  centers.  Start  the  machine  up  slowly  and  see 
that  the  oil  rings  in  bearings  are  in  motion.  As  the  machine 


Fig.  91.    Method  of  raising  an  armature. 

comes  up  to  speed,  tighten  the  belt  till  it  runs  smoothly,  and  run 
the  machine  long  enough  without  load  to  make  sure  that  the  bear- 
ings are  in  perfect  condition.  The  bearings,  when  running, 
should  be  examined  at  least  once  a  week. 


iCARE  OF  COMMUTATOR. 
The  commutator  brushes  and  brush-holders  should  at  all 
times  be  kept  perfectly  clean  and  free  from  carbon  or  other  dust. 
Wipe  the  commutator  from  time  to  time  with  a  piece  of  canvas 
lightly  coated  with  vaseline.  Lubricant  of  any  kind  should  be 
applied  very  sparingly. 


76  HANDBOOK   ON   ENGINEERING. 

If  a  commutator  when  set  up  begins  to  give  trouble  by  rough- 
ness, with  attendant  sparking  and  excessive  heating,  it  is  neces- 
sary to  immediately  take  measures  to  smooth  the  surface.  Any 
delay  will  aggravate  the  trouble,  and  eventually  cause  high  tem- 
peratures, throwing  off  solder,  and  possibly  displacement  of  the 
segments.  No.  0  sandpaper,  fitted  to  a  segment  of  wood,  with  a 
radius  equal  to  that  of  the  commutator,  if  applied  in  time  to  the 
surface  when  running  at  full  speed  (and  if  possible  with  brushes 
raised),  and  kept  moving  laterally  back  and  forth  on  the  commu- 
tator, will  usually  remedy  the  fault. 


DIRECTIONS  FOR  STARTING  DYNAMOS. 

General*  —  Make  sure  that  the  machine  is  clean  throughout, 
especially  the  commutator,  brushes,  electrical  connections,  etc. 
Remove  any  metal  dust,  as  it  is  very  likely  to  make  a  ground  or 
short  circuit. 

Examine  the  entire  machine  carefully,  and  see  that  there  are 
no  screws  or  other  parts  that  are  loose  or  out  of  place.  See  that 
the  oil-cups  have  a  sufficient  supply  of  oil,  and  that  the  passages 
for  the  oil  are  clean  and  the  feed  is  at  the  proper  rate.  In  the 
case  of  self -oiling  bearings,  see  that  the  rings  or  other  means  for 
carrying  the  oil  work  freely.  See  that  the  belt  is  in  place  and 
has  the  proper  tension.  If  it  is  the  first  time  the  machine  is 
started,  it  should  be  turned  a  few  times  by  hand,  or  very  slowly, 
in  order  to  see  if  the  shaft  revolves  easily  and  the  belt  runs  in 
center  of  pulleys. 

The  brushes  should  now  be  carefully  examined  and  adjusted 
to  make  good  contact  with  the  commutator  and  at  the  proper 
point,  the  switches  connecting  the  machine  to  the  circuit  being 
left  open.  The  machine  should  then  be  started  with  care  and 
brought  up  to  full  speed,  gradually  if  possible;  and  in  any  case 


HANDBOOK    ON    ENGINEERING.  77 

the  person  who  starts  either  a  dynamo  or  a  motor  should  closely 
watch  the  machine  and  everything  connected  with  it,  and  be  ready 
to  throw  it  out  of  circuit  if  it  is  connected,  and  shut  down  and 
stop  it  instantly  if  the  least  thing  seems  to  be  wrong,  and  should 
then  be  sure  to  find  out  and  correct  the  trouble  before  starting 
again. 

STARTING  A  DYNAMO. 

In  the  case  of  a  dynamo  it  is  usually  brought  up  to  speed 
either  by  starting  up  a  steam-engine  or  by  connecting  the 
dynamo  to  a  source  of  power  already  in  motion.  The  former 
should,  of  course,  only  be  attempted  by  a  person  competent  to 
manage  steam-engines  and  familiar  with  the  particular  type  in 
question.  This  requires  special  knowledge  acquired  by  experi- 
ence, as  there  are  many  points  to  consider  and  attend  to,  the 
neglect  of  any  of  which  might  cause  serious  trouble.  For  ex- 
ample, the  presence  of  water  in  the  cylinder  might  knock  out  the 
cylinder-head  ;  the  failure  to  set  the  feed  of  the  oil-cups  properly 
might  cause  the  piston-rod,  shaft,  or  other  part,  to  cut.  And 
other  great  or  small  damage  might  be  done  by  ignorance  or  care- 
lessness. The  mere  mechanical  connecting  of  a  dynamo  to  a 
source  of  power  is  usually  not  very  difficult;  nevertheless,  it 
should  be  done  carefully  and  intelligently,  even  if  it  only  requires 
throwing  in  a  friction-clutch  or  shifting  a  belt  from  a  loose  pul- 
ley. To  put  a  belt  on  a  pulley  in  motion  is  difficult  and  danger- 
ous, particularly  if  the  belt  is  large  or  the  speed  is  high,  and 
should  not  be  tried  except  by  a  person  who  knows  just  how  to  do 
it.  Even  if  a  stick  is  used  for  this  purpose,  it  is  apt  to  be  caught 
and  thrown  around  by  the  machinery,  unless  it  is  used  in  exactly 
the  right  way. 

It  has  been  customary  to  bring  dynamos  to  full  speed  before 
the  brushes  are  lowered  into  contact  with  the  commutator ;  but 


78  HANDBOOK    ON    ENGINEERING. 

this  is  not  necessary,  provided  the  dynamo  is  not  allowed  to  turn 
backwards,  which  sometimes  occurs  from  carelessness  in  starting, 
and  might  injure  copper  brushes  by  causing  them  to  catch  in  the 
commutator.  If  the  brushes  are  put  in  contact  before  starting, 
they  can  be  more  easily  and  perfectly  adjusted  and  the  e.m.f . 
will  come  up  slowly,  so  that  any  fault  or  difficulty  will  develop 
gradually  and  can  be  corrected  ;  or  the  machine  can  be  stopped, 
before  any  injury  is  done  to  it  or  to  the  system.  In  fact,  if  the 
machine  is  working  alone  on  a  system,  and  is  absolutely  free  from 
any  danger  of  short-circuiting  any  other  machine  or  storage  bat- 
tery on  the  same  circuit,  it  may  be  started  while  connected  to  the 
circuit,  but  not  otherwise.  If  there  are  a  large  number  of  lamps 
connected  in  the  circuit,  the  field  magnetism  and  voltage  might 
not  be  able  to  "  build  up  "  until  the  line  is  disconnected  an 
instant. 

If  one  dynamo  is  to  be  connected  with  another,  or  to  a  circuit 
having  other  dynamos  or  a  storage  battery  working  upon  it,  the 
greatest  care  should  be  taken.  This  coupling  together  of 
dynamos  can  be  done  perfectly,  however,  if  the  correct  method  is 
followed,  but  is  likely  to  cause  serious  trouble  if  any  mistake  is 
made. 

SWITCHING  DYNAHOS  INTO  CIRCUIT. 

Two  or  more  machines  are  often  connected  to  a  common  cir- 
cuit. This  is  especially  the  case  in  large  buildings  where  the 
number  of  lamps  required  to  be  fed  varies  so  much  that  one 
dynamo  may  be  sufficient  for  certain  hours,  but  two,  three  or 
more  machines  may  be  required  at  other  times.  The  various 
ways  in  which  this  is  done  depending  upon  the  character  of  the 
machines  and  of  the  circuit  and  the  precautions  necessary  in 
each  case  make  this  a  most  important  and  interesting  subject, 
which  requires  careful  consideration. 

Dynamos  may  be  connected  together  either  in  parallel  (mul- 
tiple arc)  or  in  series. 


HANDBOOK    ON    ENGINEERING.  79 


DYNAMOS  IN  PARALLEL. 

In  this  case  the  +  terminals  are  connected  together  or  to  the 
same  line,  and  the  —  terminals  are  connected  together  or  to  the 
other  line.  The  currents  (i.  e.  amperes)  of  the  machines  are 
thereby  added,  but  the  e.m.f .  (volts)  are  not  increased.  The 
chief  condition  for  the  running  of  dynamos  in  parallel  is  that 
their  voltages  shall  be  equal,  but  their  current  capacities  may  be 
different.  For  example :  A  dynamo  producing  10  amperes  may 
be  connected  to  another  generating  100  amperes,  provided  the 
voltages  agree.  Parallel  working  is,  therefore,  suited  to  constant 
potential  circuits.  A  dynamo  to  be  connected  in  parallel  with 
others  or  with  a  storage  battery,  must  first  be  brought  up  to  its 
proper  speed,  e.m.f.,  and  other  working  conditions,  otherwise, 
it  will  short-circuit  the  system,  and  probably  burn  out  its 
armature.  Its  field  magnetism  must,  therefore,  be  at  full 
strength,  owing  to  the  fact  that  it  generates  no  e.m.f.  with 
no  field  magnetism.  Hence,  it  is  "well  to  find  whether  the  pole 
pieces  are  strongly  magnetized  by  testing  them  with  a  piece  of 
iron,  and  to  make  sure  of  the  proper  working  of  the  machine  in 
all  other  respects  before  connecting  the  armature  to  the  circuit. 
It  is  a  common  accident  for  the  field-circuit  to  be  open  at  some 
point,  and  thus  cause  very  serious  results.  In  fact,  a  dynamo 
should  not  be  connected  to  a  circuit  in  parallel  with  others  until 
its  voltage  has  been  tested  and  found  to  be  equal  to,  or  slightly 
(not  over  1  or  2  per  cent)  greater  than  that  of  the  circuit.  If  the 
voltage  of  the  dynamo  is  less  than  that  of  the  circuit,  the  current 
will  flow  back  into  the  dynamo  and  cause  it  to  be  run  as  a  motor. 
The  direction  of  rotation  is  the  same,  however,  if  it  is  shunt- 
wound,  and  no  great  harm  results  from  a  slight  difference  of 
potential.  But  a  compound-wound  machine  requires  more  careful 
handling. 


80  HANDBOOK    ON    ENGINEERING. 


DIRECTIONS  FOR  RUNNING  DYNAMOS  AND  MOTORS. 

In  the  case  of  a  machine  which  has  not  been  run  before,  or 
has  been  changed  in  any  way,  it  is  of  course  wise  to  watch  it 
closely  at  first.  It  is  also  well  to  give  the  bearings  of  a  new 
machine  plenty  of  oil  at  first,  but  not  enough  to  run  on  the  arma- 
ture, commutator  or  any  part  that  would  be  injured  by  it,  and 
to  run  the  belt  rather  slack  until  the  bearings  and  belt  have  got- 
ten into  easy  working  condition.  If  possible  a  new  machine 
should  be  run  without  load  or  with  a  light  one  for  an  hour  or 
two,  or  several  hours  in  the  case  of  a  large  machine ;  and  it  is 
always  wrong  to  start  a  new  machine  with  its  full  load,  or  even  a 
large  fraction  of  it. 

This  is  true  even  if  the  machine  has  been  fully  tested  by  its 
manufacturer  and  is  in  perfect  condition,  because  there  may  be 
some  fault  in  setting  it  up,  or  some  other  circumstance  which 
would  cause  trouble.  All  machinery  requires  some  adjust- 
ment and  care  for  a  certain  time  to  get  it  into  smooth  working 
order. 

When  this  condition  is  reached,  the  only  attention  required 
is  to  supply  oil  when  needed,  keep  the  machine  clean  and  see 
that  it  is  not  overloaded.  A  dynamo  requires  that  its  voltage  or 
current  should  be  observed  and  regulated  if  it  varies.  The  per- 
son in  charge  should  always  be  ready  and  sure  to  detect  the 
beginning  of  any  trouble,  such  as  sparking,  the  heating  of  any 
part  of  the  machine,  noise,  abnormally  high  or  low  speed,  etc. ; 
before  any  injury  is  caused,  and  to  overcome  it  by  following 
directions  given  elsewhere.  Those  directions  should  be  pretty 
thoroughly  committed  to  mind,  in  order  to  facilitate  the  prompt 
detection  and  remedy  of  any  trouble  when  it  suddenly  occurs,  as 
is  apt  to  be  the  case.  If  possible,  the  machine  should  be  shut 


HANDBOOK    ON    ENGINEERING. 


81 


down  instantly  when  any  trouble  or  indication  of  one  appears,  in 
order  to  avoid  injury  and  give  time  for  examination. 

Keep  all  tools  or  pieces  of  iron  or  steel  away  from  the  machine 
while  running,  as  they  might  be  drawn  in  by  the  magnetism,  and 
perhaps  get  between  the  armature  and  pole-pieces  and  ruin  the 
machine.  For  this  reason,  use  a  zinc,  brass  or  copper  oil-can 
instead  of  iron  or  "  tin  "  (tinned  iron). 

Particular  attention  and  care  should  be  given  to  the  commu- 
tator and  brushes  to  see  that  the  former  keeps  perfectly  smooth 
and  that  the  latter  are  in  proper  adjustment.  (See  Sparking). 

Never  lift  a  brush  while  the  machine  is  delivering  current, 
unless  there  are  one  or  more  other  brushes  on  the  same  side  to 
carry  the  current,  as  the  spark  might  make  a  bad  burnt  spot  on 
the  commutator. 

Touch  the  bearing's  and  field-coils  occasionally  to  see  that 
they  are  not  hot.  To  determine  whether  the  armature  is  running 
hot,  place  the  hand  in  the  current  of  air  thrown  out  from  it  by 
centrifugal  force. 

Special  care  should  be  observed  by  any  one  who  runs  a  dynamo 
or  motor  to  avoid  overloading  it,  because  this  is  the  cause  of  most 
of  the  troubles  which  occur. 


BATTERIES. 


Name  of  Cell. 

E.M.F. 

Material  in  Plates. 

Electrolyte. 

Bunsen      .     . 

1.95 

Zinc. 

Carbon. 

Nitric  and  Sulphuric  Acid. 

Grove    . 

1.93 

« 

ft 

a         it             tt                {t 

Gravity      .     . 

LOG 

a 

Copper. 

(  Copper  Sulphate. 
\  Zinc             " 

Leclanche 

1.45 

<( 

Carbon. 

Sal  Ammoniac. 

Dry  Cell    .     . 

1.49 

tt 

f< 

Sal  Ammoniac  Paste. 

EdisonLelande 

0.9 

u 

CopperOxide 

Caustic  Potash. 

Lead  Storage  . 

1.98 

Lead. 

Lead. 

Sulphuric  Acid. 

-32  HANDBOOK   ON    ENGINEERING. 


CHAPTER    VIII. 

WHY  COMMUTATOR  BRUSHES  SPARK  AND  WHY  THEY  DO 

NOT  SPARK. 

A  long  list  of  reasons  might  be  given  why  commutator  brushes 
spark,  and  why  they  do  not  spark,  but  by  such  a  procedure  no 
light  would  ,be  thrown  on  the  subject,  because  the  reasons  would 
not  be  understood  unless  fully  explained.  It  is  preferable  to 
explain  the  subject  and  let  the  reader  tabulate  the  reasons  after 
digesting  the  explanation  of  the  principles  involved. 

Whenever  an  electric  current  is  interrupted,  a  spark  is  pro- 
duced and  it  makes  no  difference  how  the  current  is  generated, 
or  what  kind  of  a  conductor  it  is  flowing  through.  To  break 
a  current  without  a  spark  is  not  a  possibility;  hence,  if  we 
desire  to  open  a  circuit  without  producing  a  spark,  the  only  way 
to  accomplish  the  result  is  by  killing  the  current  before  the 
circuit  is  opened.  The  brushes  resting  on  the  commutator  of  a 
motor  or  a  generator  have  to  transmit  to  the  armature  and  take 
away  from  it  the  current  that  is  generated,  in  the  case  of  a 
generator,  or  the  current  that  drives  the  machine  in  the  case  of  a 
motor.  If  the  brushes  were  made  so  narrow  that  they  could  only 
make  contact  with  one  commutator  segment  at  a  time,  it  would 
be  impossible  to  run  the  machine  without  producing  very  destruc- 
tive sparks.  Commutators,  however,  are  not  made  in  this  way. 
The  insulation  between  the  segments  is  narrow,  and  the  brushes 
are  wide  enough  to  be  always  in  contact  with  two  segments,  and 
part  of  the  time  with  three.  Suppose  that  the  proportions  are 
such  that  during  most  of  the  time  the  brush  only  touches  two 


HANDBOOK    ON    ENGINEERING.  83 

segments,  as  shown  in  Fig.  92.  With  these  proportions  it  will  be 
seen,  that  so  long  as  there  are  two  segments  in  contact  with  each 
brush,  it  is  a  possibility  \>r  the  current  to  be  diverted  through 
one  of  them  only.  Suppose  that  at  the  instant  when  the  forward 
segment  is  passing  from  under  the  brush,  all  the  current  flows 
through  the  rear  segment ;  then  it  is  quite  evident  that  the  first- 
named  segment  will  break  away  from  contact  with  the  brush  with- 
out making  a  spark,  for  there  will  be  no  current  flowing  from  it 
to  the  brush. 

All  the  foregoing:  is  self-evident,  but  it  will  be  suggested  that 
although  the  brush  can  break  away  from  the  front  segment  with- 
out producing  a  spark,  it  cannot  do  the  same  thing  with  the  rear 
segment,  for  all  the  current  is  flowing  through  this  one.  While 
it  is  true  that  when  the  forward  segment  passed  from  under  the 
brush  all  the  current  was  flowing  through  the  rear  segment,  it  is 
not  true  that  the  current  continues  to  follow  this  path.  As  soon 
as  the  front  segment  passes  from  under  the  brush,  the  rear  one 
becomes  the  forward  segment,  and  while  it  is  advancing  to  the 
point  where  it  must  pass  from  under  the  brush,  the  current  can 
be  transferred  to  the  next  segment  back  of  it  which  now  plays 
the  part  of  rear  segment.  Thus  we  see  that  to  be  able  to  run  a 
machine  without  producing  sparks  at  the  commutator,  all  we  have 
to  do  is  to  provide  means  whereby  the  current  is  transferred  from 
one  segment  to  the  one  back  of  it  as  the  commutator  revolves,  so 
that  when  the  segments  pass  from  under  the  brush  there  is  no 
current  flowing  through  them.  This  result  is  accomplished  more 
or  less  perfectly  in  all  machines,  made  by  responsible  firms. 
There  are  machines  on  the  market  that  have  been  designed  by 
men  who  are  not  well  enough  posted  in  the  principles  of  electrical 
science  to  obtain  proper  proportions,  and  these  are  not  propor- 
tioned so  as  to  shift  the  current  from  the  forward  to  the  rear 
segment  as  fast  as  the  machine  revolves ;  such  machines  always 
produce  more  or  less  serious  sparking. 


84  HANDBOOK    ON    ENGINEERING. 

If  a  machine  is  accurately  made  and  the  armature  coils  and 
commutator  segments  are  properly  spaced  and  sufficient  in  num- 
ber, it  is  possible  to  get  the  brushes  so  there  will  be  little  or  no 
spark  at  a  given  load  ;  but  if  the  current  strength  be  increased  or 
reduced,  the  sparks  will  appear,  and  the  more  the  current  is 
changed  the  larger  the  sparks  will  be,  the  increasing  current 
producing  the  greatest  sparking. 

The  way  in  which  the  current  is  shifted  from  the  front  to  the 
rear  segment  will  be  explained  in  connection  with  Fig.  92.  In  this 
figure,  A  represents  a  portion  of  the  core  of  a  ring  armature. 
The  shaft  upon  which  it  is  mounted  is  shown  at  D,  and  P  N  are 
the  corners  of  the  poles  between  which  it  rotates.  The  small 
blocks  C  represent  a  portion  of  the  commutator  segments,  which 
we  have  placed  outside  of  the  armature,  so  as  to  make  the  diagram 
as  simple  as  possible.  For  the  same  reason  we  have  shown  the 
armature  coils  as  made  of  two  turns  of  wire  each.  The  line  F 
divides  the  space  between  the  ends  of  the  poles  into  two  equal 
parts,  and  the  line  E  divides  the  armature  into  two  halves 
on  which  the  directions  of  the  induced  currents  is  opposite.  In 
all  the  coils  to  the  right  of  line  E  the  currents  are  induced  in 
a  direction  away  from  the  shaft,  and  in  all  the  coils  to  the  left 
of  line  E  the  currents  flow  toward  the  shaft,  all  of  which  is 
clearly  indicated  by  the  arrow  heads  placed  upon  the  lines  repre- 
senting the  coils.  The  outline  B  represents  the  end  of  one  of  the 
brushes,  and  from  the  direction  in  which  it  is  inclined  it  will  be 
understood  that  the  armature  revolves  in  a  direction  counter  to 
that  of  the  hands  of  a  clock. 

When  the  armature  is  in  the  position  shown,  the  current  flow- 
ing in  the  coils  to  the  right  of  line  E  passes  to  segment  &,  and 
thus  reaches  the  brush,  while  the  current  flowing  in  the  coils 
to  the  left  of  line  E  reaches  segment  a,  and  through  this  passes 
to  the  brush.  As  the  brush  rests  upon  segments  a  and  b  the 
coil  with  which  they  connect  is  short-circuited,  and  therefore  a 


HANDBOOK    ON    ENGINEERING. 


85 


current  can  flow  in  it  in  any  direction,  or  there  may  be  no  cur- 
rent. To  be  able  to  run  without  spark,  or  to  obtain  perfect 
commutation,  as  it  is  called,  the  current  in  this  short-circuited 
coil,  when  in  the  position  shown,  should  be  zero,  or  nearly  so. 
This  coil,  which  is  short-circuited  by  the  brush,  is  called  the  corn- 
mutated  coil,  or  the  coil  undergoing  commutation.  It  will  be 
noticed  that  this  commutated  coil  is  in  a  position  just  forward  of 


Fig.  02.    Portion  of  core  of  ring  armature. 

the  line  E ;  hence,  the  action  of  pole  P  will  be  to  develop  a 
current  in  it  that  will  flow  in  the  same  direction  as  the  current 
in  the  coils  ahead  of  it,  that  is,  in  the  coils  to  the  left.  Now  if 
this  current  flowed  through  the  brush,  it  would  be  in  a  direction 
contrary  to  that  of  the  arrow  at  a;  hence  it  would  act  to  check 
the  current  flowing  from  the  front  segment  a  to  the  brush,  and 
would  divert  it  through  the  commutated  coil  to  the  rear  segment 


86  HANDBOOK    ON    ENGINEERING. 

b.  If  the  action  of  pole  P  upon  the  commutated  coil  is  sufficiently 
vigorous,  the  current  developed  in  it  will  be  as  strong  as  the  cur- 
rent in  the  coils  ahead  of  it,  by  the  time  the  end  of  the  segment 
is  about  to  break  away  from  the  brush  ;  and  this  being  the  case 
there  will  be  no  current  from  segment  a  to  the  brush,  and  conse- 
quently, no  spark.  If  the  action  of  pole  P  is  not  strong  enough, 
then  there  will  be  a  small  current  from  segment  a  to  the  brush 
when  they  separate,  and  as  a  result,  a  small  spark.  If  the  action 
of  pole  P  on  the  commutated  coil  is  too  vigorous,  then  the  current 
developed  in  it  will  be  too  great,  and  it  will  not  only  divert  all 
the  current  coming  from  the  forward  coils,  through  the  commuta- 
ted coil  to  segment  &,  but  in  addition  will  develop  a  local  current 
that  will  circulate  through  the  end  of  the  brush,  and,  therefore, 
when  the  separation  occurs,  there  will  be  a  current  flowing  from 
the  brush  to  the  front  segment,  and  consequently  a  spark. 

If  the  commutated  coil  were  placed  astride  of  line  E,  the 
action  of  pole  P  upon  it  would  be  no  greater  than  that  of  pole  N,  so 
that  no  current  would  be  developed  in  it  while  undergoing  com- 
mutation. The  farther  the  coil  is  in  advance  of  line  J£,  when  short- 
circuited  by  the  brush,  the  stronger  the  action  of  pole  P  upon  it ; 
therefore,  the  strength  of  the  current  developed  in  the  commutated 
coil  can  be  increased  by  moving  the  brush  farther  away  from  pole  P. 
Hence,  by  trial,  a  point  can  be  found  where  the  current  developed 
will  be  just  sufficient  for  the  purpose  and  no  more.  This  is  true, 
supposing  the  current  developed  by  the  armature  to  remain  con- 
stant, but,  if  it  varies,  the  current  in  the  commutated  coil  will  be 
either  too  great  or  too  small.  If,  when  the  brushes  are  set,  the 
armature  is  delivering  a  current  of,  say,  twenty  amperes,  then  the 
current  flowing  through  the  coils  to  the  left  of  the  brush  will  be 
ten  amperes,  and  the  current  in  the  commutated  coil  will  also  be 
ten  amperes.  If  the  armature  current  increases  to  forty  amperes, 
the  current  in  the  forward  coils  will  be  twenty  amperes,  and  as  that 
in: the  commutated  coils  will  still  be  ten  amperes,  it  will  have  only 


HANDBOOK   ON   ENGINEERING.  87 

one-half  the  strength  required  for  perfect  commutation.  In  prac- 
tice, however,  it  is  found  that  if  the  commutator  have  a  sufficient 
number  of  segments,  and  the  proportions  of  the  machine  are  such 
that  the  line  E  remains  practically  in  the  same  position  for  all 
strengths  of  armature  current,  then,  if  the  brushes  are  set  so  as  to 
run  sparkless  with  an  average  load,  they  will  run  so  nearly  spark- 
less  with  a  heavy  or  light  load  as  to  make  it  difficult  to  detect  the 
difference. 

Even  when  a  machine  is  properly  proportioned,  the  brushes 
may  spark  badly  if  they  are  not  set  in  the  proper  position  and 
with  the  proper  tension.  If  the  tension  is  not  right,  they  will 
spark  no  matter  where  they  are  set.  If  the  tension  is  too  light, 
they  will  spark,  because  they  will  chatter  and  thus  jump  off  the 
surface  of  the  commutator.  If  the  tension  is  too  great,  they  will 
spark  because  they  will  cut  the  commutator,  and  then  the  latter 
will  act  as  a  file  or  grindstone  and  cut  away  particles  from  the 
brushes,  and  these  will  conduct  the  current  from  segment  to  seg- 
ment, as  well  as  from  the  segment  to  the  brush.  Whenever  a  com- 
mutator is  seen  to  be  covered  with  fine  sparks,  some  of  which  run 
all  the  way  around  the  circle,  it  may  be  depended  upon  that  the 
surface  is  rough,  due  in  most  cases  to  too  much  pressure  on  the 
brushes,  and  the  remedy  is  to  smoothitup  and  reduce  the  tension 
and  set  the  brushes  where  they  will  run  with  the  smallest  spark. 
When  the  brushes  begin  to  spark  they  rarely  cure  themselves  and 
the  longer  they  are  allowed  to  run  with  a  heavy  spark  the  worse 
they  will  get. 

Of  all  the  troubles  which  may  occur,  sparking  is  the  only  one 
which  is  very  different  in  the  different  types  of  machines.  In 
some  its  occurrence  is  practically  impossible.  In  others,  it  may 
result  from  a  number  of  causes.  The  following  cases  of  sparking 
apply  to  nearly  all  machines,  and  they  cover  closed-coil  dynamos 
and  motors  completely. 

Cause  J*  —  Brushes  not  set  at  the  neutral  point. 


88  HANDBOOK    ON    ENGINEERING. 

Symptom*  —  Sparking,  varied  by  shifting  the  brushes  with 
rocker-arm. 

Remedy* —  Carefully  shift  brushes  backwards  or  forwards 
until  sparking  is  reduced  to  a  minimum. 

The  usual  position  for  brushes  in  two-pole  machines  is 
opposite  the  spaces  between  the  pole-pieces. 

Cause  2*  —  Commutator  rough,  eccentric,  or  has  one  or  more 
"  high  bars  "  projecting  beyond  the  others,  or  one  or  more  flat 
bars,  commonly  called  "  flats,"  or  projecting  mica,  any  one  of 
which  causes  brush  to  vibrate,  or  to  be  actually  thrown  out  of 
contact  with  commutator. 

Symptom*  —  Note  whether  there  is  a  glaze  or  polish  on  the 
commutator,  which  shows  smooth  working  ;  touch  revolving  com- 
mutator with  tip  of  finger-nail,  and  the  least  roughness  is 
perceptible,  or  feel  of  brushes,  to  see  if  there  is  any  jar.  If  the 
machine  runs  at  high-voltage  (over  250),  the  commutator  or 
brushes  should  be  touched  with  a  small  stick  or  quill  to  avoid 
danger  of  shock.  In  the  case  of  an  eccentric  commutator,  careful 
examination  shows  a  rise  and  fall  of  the  brush  when  commutator 
turns  slowly,  or  a  chattering  of  brush  when  running  fast. 

Remedy*  —  Smooth  the  commutator  with  a  fine  file  or  fine  sand- 
paper, which  should  be  applied  by  a  block  of  wood  which  exactly 
fits  the  commutator  (in  latter  case,  be  careful  to  remove  any  sand 
remaining  afterward  ;  and  never  use  emery) .  If  bearing  is  loose 
put  in  new  one.  If  commutator  is  very  rough  or  eccentric,  it 
should  be  taken  out  and  turned  off. 

Cause  3*  —  Brushes  make  poor  contact  with  commutator. 

Symptom*  —  Close  examination  shows  that  brushes  touch  only 
at  one  corner,  or  only  in  front  or  behind,  or  there  is  dirt  on  sur- 
face of  contact.  Sometimes,  owing  to  the  presence  of  too  much 
oil  or  from  other  cause,  the  brushes  and  commutator  become  very 
dirty  and  covered  with  smut.  They  should  then  be  carefully 
cleaned  by  wiping  with  oily  rag  or  benzine,  or  by  similar  means. 


HANDBOOK    ON    ENGINEERING.  89 

Occasionally  a  "  glass-hard  "  carbon  brush  is  met  with.  It 
is  incapable  of  wearing  to  a  good  seat  or  contact  and  will  only 
touch  in  one  or  two  points,  and  should  be  discarded. 

Remedy*  —  File,  bend,  adjust  or  clean  brushes  until  they  rest 
evenly  on  commutator,  with  considerable  surface  of  contact  and 
with  sure  but  light  pressure. 

It  sometimes  happens  that  the  brushes  make  poor  contact, 
because  the  brush-holders  do  not  turn  or  work  freely. 

Cause  4* —  Short-circuited  coil  in  armature  or  reversed  coil. 

Symptom*  —  A  motor  will  draw  excessive  current,  even  when 
running  free  without  load.  A  dynamo  will  require  considerable 
power  even  without  any  load. 

The  short-circuited  coil  is  heated  much  more  than  the  others, 
and  is  very  apt  to  be  burnt  out  entirely ;  therefore,  stop  machine 
immediately.  If  necessary  to  run  machine  to  locate  the  short- 
circuit,  one  or  two  minutes  is  long  enough,  but  it  may  be  re- 
peated until  the  short-circuited  coil  is  found  by  feeling  the  arma- 
ture all  over. 

An  iron  screw-driver  or  other  tool  held  between  the  field- 
magnets  near  the  revolving  armature  vibrates  very  perceptibly 
as  the  short-circuited  coil  passes.  Almost  any  armature,  par- 
ticularly one  with  teeth,  will  cause  a  slight  but  rapid  vibration  of 
a  piece  of  iron  held  near  it,  but  a  short-circuit  produces  a 
much  stronger  effect  only  once  per  revolution. 

The  current  pulsates  and  torque  is  unequal  at  different  parts 
of  a  revolution,  these  being  particularly  noticeable  when  arma- 
ture turns  rather  slowly.  If  a  large  portion  of  the  armature  is 
short-circuited,  the  heating  is  distributed  and  harder  to  locate. 
In  this  case  a  motor  runs  very  slowly,  giving  little  power,  but 
having  full-field  magnetism. 

Remedy*  —  A  short  circuit  is  often  caused  by  a  piece  of  solder 
or  other  metal  getting  between  the  commutator  bars  or  their  con- 
nections with  the  armature,  and  sometimes  the  insulation  between 


90  HANDBOOK    ON    ENGINEERING. 

or  at  the  ends  of  these  bars  is  bridged  over  by  a  particle  of  metal. 
In  any  such  case  the  trouble  is  easily  found  and  corrected.  If, 
however,  the  short-circuit  is  in  the  coil  itself,  the  only  real  cure  is 
to  rewind  the  coil. 

One  or  more  ' '  grounds  ' '  in  the  armature  may  produce  effects 
similar  to  those  arising  from  a  short  circuit. 

Cause  5*  —  Broken  circuit  in  armature. 

Symptom*  —  Commutator  flashes  violently  while  running,  and 
commutator-bar  nearest  the  break  is  badly  cut  and  burnt ;  but  in 
this  case  no  particular  armature  coil  will  be  heated,  as  in  the  last 
case  and  the  flashing  will  be  very  much  worse,  even  when  turn- 
ing slowly.  This  trouble,  which  might  also  be  confounded 
with  a  bad  case  of  "  high- bar  "  or  eccentricity  in  commutator 
(sparking),  is  distinguished  from  it  by  slowly  turning  the  arma- 
ture, when  violent  flashing  will  continue  if  circuit  is  broken, 
but  not  with  eccentric  commutator  or  even  with  "  high  bar." 

Remedy*  —  The  trouble  is  often  found  where  the  armature 
wires  connect  with  the  commutator  and  not  in  the  coil  itself,  and 
the  break  may  be  repaired  or  the  loose  wire  may  be  resoldered  or 
screwed  back  in  place.  If  the  trouble  is  due  to  a  broken  com- 
mutator connection  and  it  cannot  be  fixed,  then  connect  the  dis- 
connected bar  to  the  next  by  solder,  or  "  stagger  "  the  brushes  ; 
that  is,  put  one  a  little  forward  and  the  other  back  so  as  to  bridge 
over  the  break.  If  the  break  is  in  the  coil  itself,  rewinding  is 
generally  the  only  cure. 

Cause  6* —  Weak  field-magnetism. 

Symptom* — Any  considerable  vibration  is  almost  sure  to  pro- 
duce sparking,  of  which  it  is  a  common  cause.  This  sparking 
may  be  reduced  by  increasing  the  pressure  of  the  brushes  on  the 
commutator,  but  the  vibration  itself  should  be  overcome  by  the 
remedies  referred  to  above. 

Cause  7*  —  Chatter  of  Brushes.     The  commutator  sometimes 


HANDBOOK   ON   ENGINEERING.  91 

becomes  sticky  when  carbon  brushes  are  used,  causing  friction, 
which  throws  the  brushes  into  rapid  vibration  as  the  commutator 
revolves,  similarly  to  the  action  of  a  violin-bow. 

Symptom* —  Slight  tingling  or  jarring  is  felt  in  brushes. 

Remedy*  — Clean  commutator  and  oil  slightly.  This  stops  it 
at  once. 

NOISE. 

Cause  8*  —  Vibration  due  to  armature  or  pulley  being  out  of 
balance. 

Symptom* — Strong  vibration  felt  when  the  hand  is  placed 
upon  the  machine  while  it  is  running.  Vibration  changes  greatly 
if  speed  is  changed. 

Remedy* — The  easiest  method  of  finding  in  which  direction 
the  armature  is  out  of  balance  is  to  take  it  out  and  rest  the  shaft 
on  two  parallel  and  horizontal  A-shaped  metallic  tracks  suffici- 
ently far  apart  to  allow  the  armature  to  go  between  them.  If  the 
armature  is  then  slowly  rolled  back  and  forth,  the  heavy  side  will 
tend  to  turn  downward.  The  armature  and  pulley  should  always 
be  balanced  separately.  An  excess  of  weight  on  one  side  of  the 
pulley  and  an  equal  excess  of  weight  on  the  opposite  side  of  the 
armature  will  not  produce  a  balance  while  running,  though  it^ 
does  when  standing  still ;  on  the  contrary,  it  will  give  the  shaft 
a  strong  tendency  to  "wobble."  A  perfect  balance  is  only 
obtained  when  the  weights  are  directly  opposite,  i.  e.,  in  the 
same  line  perpendicular  to  the  shaft. 

Cause  9*  —  Armature  strikes  or  rubs  against  pole  pieces. 

Symptom* — Easily  detected  by  placing  the  ear  near  the  pole- 
pieces,  or  by  examining  armature  to  see  if  its  surface  is  abraded 
at  any  point,  or  by  examining  each  part  of  the  space  between 
armature  and  field,  as  armature  is  slowly  revolved,  to  see  if  any 


92  HANDBOOK    ON    ENGINEERING. 

portion  of  it  touches  or  is  so  close  as  to  be  likely  to  touch  when 
the  machine  is  running.  Or  turn  armature  by  hand  when  no 
current  is  on,  and  note  if  it  sticks  at  any  point. 

Remedy.  —  Bind  down  any  wire,  or  other  part  of  the  armature 
that  may  project  abnormally,  or  file  out  the  pole-pieces  where  the 
armature  strikes,  or  center  the  armature  so  that  there  is  a  uni- 
form clearance  between  it  and  the  pole-pieces  at  all  points. 

Cause  JO*  —  Singing  or  hissing  of  brushes.  This  is  usually 
occasioned  by  rough  or  sticky  commutator,  or  by  tips  of  brushes 
not  being  smooth,  or  the  layers  of  a  copper  brush  not  being  held 
together  and  in  place.  With  carbon  brushes,  hissing  will  be  caused 
by  the  use  of  carbon  which  is  gritty  or  too  hard.  Vertical  carbon 
brushes,  or  brushes  inclined  against  the  direction  of  rotation,  are 
apt  to  squeak  or  sing.  A  new  machine  will  sometimes  make 
noise  from  rough  commutator,  no  matter  how  carefully  it  is 
turned  off,  because  the  difference  in  hardness  between  mica  and 
copper  causes  the  cut  of  the  tool  to  vary,  thus  forming  inequali- 
ties which  are  very  minute,  but  enough  to  make  noise.  This 
can  be  best  smoothed  by  running. 

Remedy*  —  Apply  a  very  little  oil  or  vaseline  to  the  com- 
mutator with  the  finger  or  a  rag.  Adjust  the  brushes  or  smooth 
the  commutator.  Carbon  brushes  are  apt  to  squeak  in  starting 
up,  or  at  slow  speed.  This  decreases  at  full  speed,  and  can 
usually  be  reduced  by  moistening  the  brush  with  oil,  care  being 
taken  not  to  have  a  ay  drops,  or  excess  of  oil.  Shortening  or 
lengthening  the  brushes  sometimes  stops  the  noise.  Run  the 
machine  on  open  circuit  until  commutator  and  brushes  are 
worn  smooth. 

For  alternating  current  machinery  and  principles  of  alternating 
current  see  page  815. 


HANDBOOK   ON   ENGINEERING.  93 


HEATING  IN  DYNAHO  OR  MOTOR. 

General  Instructions*  — The  degree  of  heat  that  is  injurious  or 
objectionable  in  any  part  of  a  dynamo  or  motor  is  easily  deter- 
mined by  feeling  the  various  parts.  If  the  heat  is  bearable  for  a 
few  moments,  it  is  entirely  harmless.  But  if  the  heat  is  unbear- 
able for  more  than  a  few  seconds,  the  safe  limit  of  temperature 
has  been  passed,  except  in  the  case  of  commutators  in  which 
solder  is  not  used  ;  and  it  should  be  reduced  in  some  of  the  ways 
that  are  given  above.  In  testing  with  the  hand,  allowance  should 
always  be  made  for  the  fact  that  bare  metal  feels  much  hotter 
than  cotton,  etc.  If  the  heat  has  become  so  great  as  to  produce 
an  odor  or  smoke,  the  safe  limit  has  been  far  exceeded  and  the 
current  should  be  shut  off  and  the  machine  stopped  immediately, 
as  this  indicates  a  serious  trouble,  such  as  a  short-circuited  coil  or 
a  tight  bearing.  The  machine  should  not  again  be  started  until 
the  cause  of  the  trouble  has  been  found  and  positively  overcome. 
Of  course  neither  water  nor  ice  should  ever  be  used  to  cool  elec- 
trical machinery,  except  possibly  the  bearings  of  large  machines, 
where  it  can  be  applied  without  danger  of  wetting  the  other 
parts. 

Feeling  for  heat  will  answer  in  ordinary  cases,  but  of  course, 
the  sensitiveness  of  the  hand  differs,  and  it  makes  a  very  great 
difference  whether  the  surface  is  a  good  or  bad  conductor  of  heat. 
The  back  of  the  hand  is  more  sensitive  and  less  variable  than  the 
palm  for  this  test.  But  for  accurate  results  a  thermometer 
should  be  applied  and  covered  with  waste  or  cloth  to  keep  in 
the  heat.  In  proper  working  the  temperature  of  no  parts  of 
the  machine  should  rise  more  than  45°  C.,  or  81°  F.  above  the  tem- 
perature of  the  surrounding  air.  If  the  actual  temperature  of 


94  HANDBOOK   ON   ENGINEERING. 

the  machine  is  near  the  boiling  point,  100°  C.,  or  212°  F.,  it  is 
seriously  high. 

It  is  very  important  in  all  cases  of  heating  to  locate  correctly 
the  source  of  heat  in  the  exact  part  in  which  it  is  produced.  It 
./s  a  common  mistake  to  suppose  that  any  part  of  a  machine  which 
is  found  to  be  hot  is  the  seat  of  the  trouble.  A  hot  bearing  may 
cause  the  avmature  or  commutator  to  heat  or  vice  versa.  In 
every  case,  all  parts  of  the  machine  should  be  felt  to  find  which 
is  the  hottest,  since  heat  generated  in  one  part  is  rapidly  diffused 
throughout  the  entire  machine.  It  is  generally  much  surer  and 
easier  in  the  end  to  make  observations  for  heating  by  starting 
with  the  whole  machine  perfectly  cool,  which  is  done  by  letting  it 
stand  for  one  or  more  hours  or  over  night,  before  making  the 
examination.  When  ready  to  try  it,  run  it  fast  for  three  to  five 
minutes,  with  the  field  magnets  charged ;  then  stop,  and  feel  all 
parts  immediately.  The  heat  will  be  found  in  the  right  place,  as 
it  will  not  have  had  time  to  diffuse  from  the  heated  to  the  cool 
parts  of  the  machine.  Whereas,  after  the  machine  has  run  some 
time,  any  heating  effect  will  spread  until  all  parts  are  equal  in 
temperature,  and  it  will  then  be  almost  impossible  to  locate  the 
trouble. 

Excessive  heating  of  commutator,  armature,  field  magnets,  or 
bearings  may  occur  in  any  type  of  dynamo  or  motor,  but  it  can 
almost  always  be  avoided  by  proper  care  and  working  conditions. 


THE  EFFECT  OF  THE  DISPLACEHENT  OF  THE  ARMATURE. 

If  a  machine  is  old,  it  is  more  than  likely  the  shaft  will  be 
found  out  of  center,  and  if  this  fact  is  discovered  at  a  time  when 
things  are  not  working  as  they  should,  it  is  taken  for  granted  this 
is  the  cause  of  the  trouble.  What  is  true  of  shafts  out  of  the 


HANDBOOK   ON   ENGINEERING. 


95 


center  is  true  of  several  other  things  that  are  liable  to  get  out  of 
place.  For  the  present  it  will  be  sufficient  to  investigate  just 
what  effect  the  displacement  of  the  shaft  can  have. 

Fig1*  93  illustrates  an  armature  of  a  two-pole  machine  which  is 
out  of  center  in  one  direction,  and  Fig.  94 shows  another  two-pole 
armature  out  of  center  in  a  direction  at  right  angles  to  that 
shown  in  the  first  figure.  The  condition  shown  in  Fig.  93  could 
be  produced  by  a  heavy  armature  running  in  rather  light  bear- 
ings for  several  years,  and  the  side  displacement  of  Fig.94could 
be  produced  by  the  tension  of  an  extra  tight  belt.  The  mechan- 


Figs.  93  and  94.    Showing  armature  out  of  center. 

ical  effect  of  both  these  conditions  would  be  to  increase  the  pres- 
sure on  the  bearings,  as  the  part  a  of  the  armature  would  be 
drawn  toward  the  poles  of  the  field  with  greater  force  than  the 
opposite  side.  The  downward  pull,  due  to  the  attraction  of  the 
magnetism,  would  be  greater  in  Fig. 9 3  than  the  side  pull  in  Fig. 
9 4  supposing  both  armatures  and  fields  to  be  the  same  in  both 
cases,  and  the  displacement  of  the  shafts  equal.  This  difference 
is  due  to  the  fact  that  in  Fig.  93  the  magnetism  of  both  poles  is 
concentrated  at  the  lower  corners  on  account  of  the  shorter  air 
gap  ;  hence  both  sides  pull  much  harder  on  the  lower  side.  In 


^(5  HANDBOOK   ON   ENGINEERING. 

Fig.  94  the  pull  of  the  N  pole  is  greater  than  that  of  the  other, 
simply  because  in  the  latter  the  magnetism  is  more  dispersed,  but 
the  difference  in  the  density  on  the  two  sides  will  not  be  very 
great.  If  the  bearings  of  a  machine,  with  the  armature  dis- 
placed, as  indicated,  have  shown  any  signs  of  cutting,  or  if  they 
run  unusually  warm,  their  condition  will  be  improved  by  putting 
in  new  bearings  that  will  bring  the  shaft  central. 

If  the  armature  is  of  the  drum  type,  the  displacement  of  the 
shaft  will  have  no  effect  upon  it  electrically.  This  is  owing  to  the 
fact  that  all  the  armature  coils  are  wound  from  one  side  of 
the  core  to  the  other,  and,  therefore,  at  all  times,  every 
coil  has  one  side  under  the  influence  of  one  pole  and  the  other 
side  under  the  influence  of  the  opposite  pole,  and  if  one 
side  is  acted  upon  strongly  by  one  pole,  it  will  be  acted 
upon  feebly  by  the  other.  If  the  armature  is  of  the  ring  type, 
then  the  displacement  of  the  shaft  will  affect  it  electrically,  for 
in  a  ring  armature,  the  coils  on  one  side  are  acted  upon  by 
the  pole  on  that  side,  only,  and  as  the  magnetic  field  from  one 
pole  will  be  stronger  than  that  from  the  other  (that  is,  considering 
the  action  upon  equal  halves  of  the  armature) ,  the  voltage  devel- 
oped in  the  coils  on  one  side  of  the  armature  will  be  greater  than 
that  developed  on  the  other  side. 

The  effect  of  the  disturbance  of  the  electrical  balance  will  be 
that  the  brushes  will  spark  badly,  because  the  voltage  of  the  cur- 
rent generated  on  one  side  of  the  armature  will  be  greater  than 
that  of  the  current  on  the  other  side.  Hence,  when  these  two 
currents  meet  at  the  brushes,  the  strong  one  will  tend  to  drive 
the  weak  one  backward.  If,  while  the  armature  is  out  of  center, 
we  wish  to  adjust  the  brushes  so  as  to  get  rid  of  the  excessive 
sparking,  all  we  have  to  do  is  to  set  them  to  the  right  of  the  cen- 
ter line,  as  in  Fig.  94  so  that  the  wire  on  the  left  side  will  cover  a 
greater  portion  of  the  circumference  than  the  right. 

. 


HANDBOOK   ON   ENGINEERING.  97 

In  a  multipolar  machine,  the  displacement  of  the  armature 
will  have  the  same  effect  mechanically  as  in  the  two-pole  type ; 
nmltipolar  armatures  are  connected  in  two  different  ways,  one  of 
which  is  called  the  wave  or  series  winding,  and  the  other  the  lap 
or  parallel  winding.  In  the  first  named  type  of  winding,  the 
ends  of  all  the  coils  on  the  armature  are  connected  with  each 
other  and  with  the  commutator  segments  in  such,  a  manner  that 
there  are  only  two  paths  through  the  wire  for  the  current ;  there- 
fore, these  two  armature  currents  pass  under  all  the  poles  and 
the  voltage  of  each  current  is  the  combined  effect  of  all  the  poles. 
From  this  very  fact,  it  can  be  clearly  seen  that  it  makes  no 
difference  what  the  distance  between  the  several  poles  and  arma- 
ture may  be,  for  if  some  are  nearer  than  the  others,  the  only 
effect  will  be  that  these  poles  will  not  develop  their  share  of  the 
total  voltage,  but  whatever  their  action  may  be,  it  will  be  the 
same  on  the  coils  in  both  circuits. 

When  a  multipolar  armature  is  connected  so  as  to  form  a 
parallel  or  lap  winding,  then  the  connections  between  the  coil 
ends,  and  between  these  ends  and  the  commutator  segments,  are 
such  that  as  many  paths  are  provided  for  the  current  as  there  are 
poles,  and  each  one  of  these  paths  is  located  under  one  pole,  and 
as  a  consequence,  the  voltage  developed  in  it  is  proportional  to 
the  action  of  this  pole.  The  diagram  Fig.  95  illustrates  a  six-pole 
armature  with  the  ends  of  the  field  poles,  and  the  arrows  a  a,  b  6, 
c  c,  indicate  the  six  separate  divisions  of  the  coils  in  which  the 
branch  currents  are  developed.  Now,  it  can  be  clearly  seen  that 
as  the  armature  is  nearer  to  the  lower  poles  than  to  any  of  the 
others,  the  action  of  these  will  be  the  strongest.  Hence,  the  cur- 
rents a  a  will  be  stronger  than  the  others  and  will  have  a  higher 
voltage. 

The  two  upper  currents  are  weaker  than  the  side  ones  and 

7 


98 


HANDBOOK   ON    ENGINEERING. 


their  voltage  is  also  lower,  so  that,  the  current  returning  to  the 
commutator  through  the  brushes  at  the  upper  corners,  will  not 
divide  equally,  but  the  larger  portion  will  be  drawn  into  the  coils 
on  the  side ;  and  as  the  upper  coils  will  have  to  fight  to  hold  their 
own,  so  to  speak,  there  will  be  a  disturbance  of  the  balance  that 


Fig.  95*    Diagram  of  six-pole  armature. 


is  re-quired  for  smooth  running.  The  result  will  be  heavy  spark- 
ing at  these  brushes.  In  the  great  majority  of  cases,  if  the  brushes 
of  a  multipolar  machine  spark  on  account  of  the  armature  being 
out  of  center,  the  only  cure  is  to  reset  the  bearings,  if  they  are 
adjustable,  and  if  they  are  not,  to  put  in  new  ones. 


HANDBOOK    ON    ENGINEERING. 


99 


Table  of  Carrying  Capacity  of  Wires*  —  Below  is  a  table  which 
must  be  followed  in  placing  interior  conductors,  showing  the 
allowable  carrying  capacity  of  wires  and  cables  of  ninety-eight 
per  cent  conductivity,  according  to  the  standard  adopted  by  the 
American  Institute  of  Electrical  Engineers. 


TABLE  A. 

TABLE  B. 

Rubber-Covered 

Weatherproof 

Wires. 

Wires. 

B.  A  S.  G. 

Amperes. 

Amperes. 

Circular  Mile. 

18 

3 

5 

1,624 

16 

6 

8 

2,583 

14 

12 

16 

4,107 

12 

17 

23 

6,530 

10 

24 

32 

10,380 

8 

33 

46 

16,510 

6 

46 

65 

26,250 

5 

54 

77 

33,100 

4 

65 

92 

41,740 

3 

76 

110 

52,630 

2 

90 

131 

66,370 

1 

107 

156 

83,690 

0 

127 

185 

105,500 

00 

150 

220 

133,100 

000 

177 

262 

167,800 

0000 

210 

312 

211,600 

Circular  MJls 

200,000 

200 

300 

300,000 

270 

400 

400,000 

330 

500 

500,000 

390 

590 

600,000 

450 

680 

700,000 

500 

760 

800.000 

550 

840 

90u,000 

600 

920 

100  HANDBOOK    ON    ENGINEERING. 


TABLE  A. 

TABLE  B. 

Rubber-Covered 

Weatherproof 

Wires. 

Wires. 

Circular  Mile. 

Amperes. 

Amperes. 

1,000,000 

650 

1,000 

1,100,000 

690 

1,080 

1,200,000 

730 

1,150 

1,300,000 

770 

1,220 

1,400,000 

810 

1,290 

1,500,000 

850 

1,360 

1,600,000 

890 

1,430 

1,700,000 

940 

1,490 

1,800,000 

970 

1,550 

1,900,000 

1,010 

17610 

2,000,000 

1,050 

1,670 

The  lower  limit  is  specified  for  rubber-covered  wires  to  pre= 
vent  gradual  deterioration  of  the  high  insulations  by  the  heat 
of  the  wires,  but  not  from  fear  of  igniting  the  insulation,  The 
question  of  drop  is  not  taken  into  consideration  in  the  above 
tables. 

Insulation  Resistance*  —  The  wiring  in  any  public  building 
must  test  free  from  grounds  ;  i.  e.,  the  complete  installation  must 
have  an  insulation  between  conductors  and  between  all  conduc- 
tors and  the  ground  (not  including  attachments,  sockets,  recep- 
tacles, etc.)  of  not  less  than  the  following:  - 

Up  to      5  amperes,  4,000,000  Up  to       200  amperes,   100,000 

"       10        "          2,000,000  "          400  25,000 

"       25        "             800,000  "          800  "             25,000 

"       50        "             400,000  "      1,600  "              12,500 
"     100        "             200,000 

All  cutouts  and  safety  devices  in  place  in  the  above. 
Where  lamp  sockets,  receptacles  and  electroliers,  etc.,  are  con- 
nected, one-half  of  the  above  will  be  required. 


HANDBOOK    ON    ENGINEERING.  101 

Soldering   Fluid* — a.  The    following  formula   for    soldering 
fluid  is  suggested :  — 

Saturated  solution  of  zinc  chloride,  5  parts. 
Alcohol,  4  parts. 

Glycerine,  1  part. 

Bell  or  Other  Wires*  —  a.  Shall   never  be  run  in  same  duct 
with  lighting  or  power  wires. 

Table  of  Capacity  of  Wires.  — 


a~ 

CO  02 

*<* 


PQ 
19 

1,288 

0 

fc 

Vr—  i 

M 
QQ 

18 

1,624 

... 

... 

3 

17 

2,048 

... 

... 

0.. 

16 

2,583 

... 

... 

6 

15 

3,257 

... 

... 

... 

14 

4,107 

... 

... 

12 

12 

6,530  . 

... 

... 

17 

... 

9,016 

7 

19 

21 

.0. 

11,368 

7 

18 

25 

... 

14,336 

7 

17 

30 

0.. 

18,081 

7 

16 

35 

... 

22,799 

7 

15 

40 

... 

30,856 

19 

18 

50 

..0 

38,912 

19 

17 

60 

..« 

49,077 

19 

16 

70 

..0 

60,088 

37 

18 

85 

... 

75,776 

37 

17 

100 

..0 

99,064 

61 

18 

120 

.0. 

124,928 

61 

17 

145 

... 

157,563 

61 

16 

170 

102 


HANDBOOK    ON    ENGINEERING. 


8 
8, 


198,677  61  15  200 

250,527  61  14  235 

296,387  91  15  270 

373,737  91  14  320 

413,639  127  15  340 

When  greater  conducting  area  than  that  of  B.  &  S.  G.  is  re- 
quired, the  conductor  shall  be  stranded  in  a  series  of  7,  19,  37, 
61,  91  or  127  wires,  as  may  be  required;  the  strand  consisting 
of  one  central  wire,  the  remainder  laid  around  it  concentrically, 
each  layer  to  be  twisted  in  the  opposite  direction  from  the  pre- 
ceding. 

TABLE    SHOWING     THE    SIZE    OF    WIRE    OF     DIFFERENT    METALS    THAT 
WILL   BE    MELTED    BY    CURRENTS    OF    VARIOUS    STRENGTHS. 


Strength 
of 
Current 
in 
Amperes. 

DIAMETER  OF  WIRE  IN  THOUSANDTHS  OF  AN  INCH. 

Copper. 

Aluminum. 

Platinum. 

•    German 
Silver. 

Iron. 

Tin. 

1 

.002 

.003 

.003 

.003 

.005 

.007 

2 

.003 

.004 

.005 

.005 

.008 

.011 

3 

.004 

.005 

.007 

.007 

.010 

.015 

4 

.005 

.006 

.008 

.008 

.012 

.018 

5 

.006 

.008 

.010 

.010 

.014 

.021 

10 

.009 

.012 

.016 

.016 

.022 

.033 

15 

.013 

.016 

.020 

.020 

.028 

.044 

20 

.015 

.019 

.025 

.025 

.034 

.053 

25 

.018 

.022 

.029 

.029 

.040 

.062 

30 

.020 

.025 

.032 

.032 

.045 

.069 

35 

.022 

.028 

.036 

.036 

.050 

.077 

40 

.025 

.030 

.039 

.039 

.055 

.084 

50 

.027 

.033 

.042 

.042 

.059 

.091 

60 

.029 

.035 

.045 

.045 

.063 

.098 

HANDBOOK    ON    ENGINEERING.  1Q3 


CHAPTER   IX. 

ARC  LIGHTING   APPARATUS. 

INSTRUCTIONS  FOR  INSTALLING   AND  OPERATING  APPARA- 
TUS FOR  ARC  LIGHTING. 

Within  the  past  few  years  the  arc  lighting  industry  has  under- 
gone a  decided  transformation,  new  systems  of  lighting,  together 
with  new  forms  of  lamps,  generators  and  accessory  apparatus, 
having  practically  superceded  the  older  types.  In  so  far  as  the 
manufacture  of  arc  lighting  apparatus  is  concerned,  the  new  has 
entirely  replaced  the  old.  The  latter,  however,  is  still  to  be 
found  in  operation  in  many  parts  of  the  country,  but  is  rapidly 
being  replaced. 

In  the  early  days  of  the  electrical  industry,  arc  lamps  were  of 
the  type  now  known  as  "  Open  arc,  "  and  were  connected  in 
series  in  circuits  that  were  supplied  with  current  from  constant 
current  generators,  commonly  called  u  Arc  dynamos.  "  In  about 
the  year  1894,  what  is  now  known  as  the  "  Enclosed  arc  "  lamps 
came  into  use.  These  lamps  found  favor  with  incandescent 
lighting  stations,  because  they  could  be  operated  successfully  on 
their  circuits,  and  were  economical  owing  to  the  fact  that  the  car- 
bons would  last  from  100  to  150  hours,  which  is  about  twenty 
times  as  long  as  they  last  in  the  open  arc  lamp. 

The  enclosed  lamps  did  not  meet  with  favor  with  the  regular 
arc  lighting  stations  because  to  burn  with  a  strong  and  steady 
light,  they  must  be  adjusted  for  a  much  longer  arc,  and  this 
means  a  much  higher  voltage,  consequently  a  smaller  number  of 
lamps  on  the  circuit.  It  can  readily  be  seen  that  no  matter  what 
the  advantages  offered  by  the  enclosed  lamp  might  be,  they 


104  HANDBOOK    ON   ENGINEERING. 

would  not  impress  an  arc  light  station  manager  favorably  when  he 
found  that  to  make  them  operate  well  he  would  have  to  reduce 
the  number  of  lamps  on  a  65  light  circuit  to  45  or  50.  Owing  to 
this  fact,  the  enclosed  lamps  were  confined  exclusively  to  the  Ed- 
ison incandescent  light  circuits  in  the  beginning  of  their  career. 
Soon  thereafter,  however,  they  began  to  be  used  on  alternating 
current  incandescent  lighting  circuits.  Next  they  found  their 
way  onto  power  circuits,  and  at  about  the  same  time  "  Arc 
lighting  "  transformers  were  devised,  by  means  of  which  lamps 
could  be  run  in  series,  with  alternating  currents,  in  precisely  the 
same  way  as  the  old  open  arc  lamps  were  run  from  arc  dynamos. 
This  latter  system,  using  "  Arc  lighting  *'  transformers,  or  regu- 
lating transformers  as  they  are  commonly  called,  in  connection 
with  the  enclosed  lamps,  may  truly  be  said  to  be  the  successor 
of  the  original  arc  lighting  system. 

Many  of  the  old  time  arc  light  dynamos  that  were  wound  for  a 
current  of  6.6  amperes,  to  operate  1200  candle  power  lamps  are 
now  used  to  operate  enclosed  arc  lamps  of  the  nominal  2000 
candle  power,  but  the  number  of  lamps  in  the  circuit  is  reduced 
to  about  two-thirds.  Some  of  the  10  ampere  dynamos  have  been 
rewound  so  as  to  give  a  current  of  6  amperes,  with  a  correspond- 
ingly increased  voltage,  and  these  also  are  used  to  operate  en- 
closed lamps.  The  manufacture  of  arc  light  generators  has  been 
abandoned  by  nearly  all  the  former  makers,  with  the  exception  of 
the  Brush  Company,  in  so  far  as  we  know.  As  the  latter  type  of 
arc  generator  is  still  made,  and  as  many  of  these  machines  are  in 
use,  and  probably  will  be  for  years  to  come,  it  is  thought  advis- 
able to  describe  it  briefly  herein. 

The  latest  type  of  brush  arc  generator  is  shown  in  Fig.  96.  This 
illustration  also  shows  the  way  in  which  the  lamp  circuits  are 
arranged.  As  will  be  noticed  there  are  four  independent  cir- 
cuits, that  are  connected  with  the  upper  set  of  binding  posts  of 
the  connection  board  in  the  upper  right  hand  corner  of  the  figure. 


HANDBOOK    ON    ENGINEERING. 


105 


The  wires  coming  from  the  generator  are  connected  with  the  lower 
set  of  binding  posts  of  the  connection  board.     By  means  of  this 


Fig.  96.    Multiple  Circuit  Brush  Arc  Lighting  Generator. 

arrangement,  it  is  possible,  as  can  be  easily  seen,  to  connect  any 
one  of  the  generator  circuits,  with  any  one  of  the  lamp  circuits. 
The  generator  is  connected  so  as  to  feed  current  into  four  circuits, 
that  are  connected  with  each  other,  but  at  the  same  time  are  in- 
dependent. The  object  of  dividing  the  current  into  four  separate 
circuits  is  to  reduce  the  voltage  on  each  one,  not  only  to  make  it 
safer,  but  also  to  reduce  the  strain  on  the  insulation.  The  old  65 
light  brush  machines  fed  current  to  open  arc  lamps  that  required 


106  HANDBOOK    ON   ENGINEERING. 

45  volts  each,  so  that  the  total  voltage  of  the  machine  was  about 
3000.  The  enclosed  arc  lamps  now  used  require  about  80  volts 
each,  so  that  to  operate  65  on  one  circuit  would  require  an  e.  m.  f. 
of  about  5000  volts,  which  would  bring  so  great  a  strain  on  the 
insulation  as  to  cause  frequent  disturbances,  not  to  say  anything 
about  the  greater  danger  the  men  operating  the  apparatus  would 
be  exposed  to. 


Fig.  97.    Diagram  Showing  Arrangement  of  Circuits  in  Brash 
Multiple  Circuit  Arc  Lighting  Generator. 

The  modern  Brush  generators  of  100  light  capacity,  develop  an 
e.  m.  f.  of  about  8000  volts,  but  as  this  is  divided  among  four 
circuits,  the  e.  m.  f.  acting  on  each  one  is  only  2000  volts. 

The  way  in  which  the  Brush  generator  is  wound  so  as  to 
supply  four  circuits,  is  easily  explained.  Looking  at  Fig.  96,  it 
will  be  seen  that  there  are  four  separate  pairs  of  commutator 


HANDBOOK   ON    ENGINEERING.  107 

rings,  each  one  of  which  is  made  the  same  as  the  single  pair  used 
on  a  single  circuit  machine.  It  will  also  be  seen  that  the  arma- 
ture is  wound  with  a  large  number  of  narrow  coils,  their  actual 

number  being  32.     If  these  coils  were  numbered  1234, 12 

34,  —  1  2  3  4,  all  the  way  around  the  circle,  then  if  the  connec- 
tions were  traced  out,  it  would  be  found  that  all  the  No.  1  coils 
are  connected  with  one  pair  of  commutator  rings,  ail  the  No.  2 
coils  with  another  pair  of  commutator  rings,  all  the  No.  3  coils 
with  the  third  set  of  rings,  and  all  the  No.  4  coils  with  the  fourth 
pair  of  commutator  rings.  This  way  of  connecting  the  armature 
coils  with  the  commutator  rings  can  be  more  fully  understood 
from  the  diagram  Fig.  97,  in  which  1,  2,  3,  4,  represent  the  four 
sets  of  armature  coils,  and,  A,  JB,  0,  Z>,  represent  the  four  lamp 
circuits.  In  looking  at  this  diagram  it  will  be  seen  that  although 
the  lamps  are  connected  in  four  independent  circuits,  these  cir- 
cuits are  not  actually  disconnected  from  each  other,  but  are  con- 
nected through  the  several  sets  of  armature  coils.  Thus  the  A 
circuit,  starts  from  the  end  of  the  No.  1  set  of  coils,  and  ends  at 
the  entering  end  of  No.  2  set  of  coils.  Passing  through  this  set 
of  coils  the  current  enters  the  B  lamp  circuit,  and  thence  passes 
through  the  No.  3  armature  coils,  to  the  C  lamp  circuit,  and 
through  the  No.  4  armature  coils  to  the  D  lamp  circuit  and  thus 
to  the  entering  end  of  the  No.  1  coils.  The  switches  a  b  c  d, 
shown  in  Fig.  97,  are  the  same  as  those  seen  on  the  switch  board 
mounted  on  the  generator  in  Fig.  96,  and  are  for  the  purpose  of 
cutting  out  any  one  of  the  lamp  circuits  if  it  is  desired. 

An  arc  light  generator  must  be  so  arranged  that  it  will  keep 
the  strength  of  the  current  uniform,  and  vary  the  voltage  in  ac- 
cordance with  the  number  of  lamps  in  operation .  The  enclosed 
lamps  require  a  current  of  about  6  amperes  so  that  the  generator 
must  be  regulated  so  as  to  give  this  amount  of  current  regard- 
less of  the  number  of  lamps  in  operation.  To  accomplish  this 
result  a  regulator  is  used,  which  is  secured  to  the  base  of  the 


108 


HANDBOOK    ON    ENGINEERING. 


generator  directly  under     the  commutator,  as  clearly  shown  in 
Fig.  96.     This  regulator  acts  by  varying  the  strength  of  the  cur- 


rent  that  passes  through  the  field  coils  of  the  generator,  and  it 
regulates  the  voltage  in  each  one  of  the  four  lamp  circuits  owing 
to  the  fact  that  these  circuits  are  connected  with  each  other 


HANDBOOK    ON   ENGINEERING. 


109 


through  the  armature  coils.  Thus  if  there  were  five  lamps  burn- 
ing in  circuit  A  and  five  in  circuit  (7  while  in  circuit  B  the  full 
number  of  25  were  in  operation,  then  the  greater  part  of  the  volt- 
age of  coils  2  and  3  would  act  on  the  fully  loaded  circuit  U, 
while  the  small  remaining  portions  would  act  on  the  lightly  loaded 
circuits  A  and  C. 


Fig.  99.    Diagram  Showing  Position  of  Brushes  on 
Brash  Generator. 

An  enlarged  view  of  the  regulator  is  shown  in  Fig.  98  at  A, 
and  the  way  in  which  it  operates  is  fully  illustrated  in  the  line 
drawing  B.  In  order  that  the  operation  of  the  regulator  may  be 
fully  understood  it  is  necessary  to  say  that  the  field  coils  of  the 
generator  are  connected  in  parallel  with  a  resistance,  and  that  the 
action  of  the  regulator  is  to  reduce  the  resistance  in  the  parallel 
circuit,  when  the  voltage  of  the  generator  is  to  be  reduced,  and 
to  increase  this  resistance  when  the  voltage  is  to  be  increased.  If 


110  HANDBOOK    ON    ENGINEERING. 

the  resistance  in  the  circuit,  that  is  parallel  with  the  field,  is  re- 
duced, more  current  will  pass  through  it,  and,  therefore,  less  cur- 
rent will  pass  through  the  generator  field  coils  hence  the  voltage 
will  be  reduced.  Increasing  the  resistance  in  the  parallel  circuit 
will  have  the  opposite  effect.  From  diagram  B,  Fig.  98,  it  will 
be  seen  that  the  regulator  is  driven  from  the  generator  shaft  by 
a  belt,  which  rotates  a  small  oil  pump  which  draws  oil  from  a 
tank  and  forces  it  through  a  valve  T,  the  ports  of  which  are 
never  completely  closed ;  so  that  even  when  it  is  in  the  central 
position  oil  can  flow  through.  The  valve  is  controlled  by  an 
electro  magnet  F  whose  armature  U  moves  lever  II.  The 
strength  of  magnet  F  varies  with  the  strength  of  the  current  gen- 
erated. A  spring  G  acts  to  pull  lever  H  in  the  opposite  direc- 
tion from  that  in  which  the  magnet  acts,  hence,  the  stronger  the 
latter  the  more  the  valve  is  raised,  and  the  weaker  it  is  the  more 
jPis  pulled  down  by  G.  The  tension  of  G  is  adjusted  by  a  nut 
R.  This  nut  is  adjusted  so  that  the  valve  T  is  held  in  the  cen- 
tral position  when  the  current  is  of  the  proper  strength.  If  the 
current  becomes  too  strong  magnet  F  pulls  down  U  and  raises  T 
thus  forcing  oil  on  the  upper  side  of  piston  S  and  allowing  it  to 
flow  out  from  the  under  side.  This  action  forces  piston  X  around 
clockwise.  The  shaft  upon  which  X  is  mounted  carries  at  its  in- 
ner end  gearing  that  moves  the  rheostat  lever  A  so  as  to  reduce 
the  resistance  and  thus  lower  the  field  current,  when  the  genera- 
tor current  drops  below  the  normal,  the  reverse  action  takes 
place,  and  resistance  is  cut  in  by  the  movement  of  A  in  the  op- 
posite direction.  When  A  is  rotated  the  gear  Z  swings  the  arm 
N  and  thus  the  position  of  the  commutator  brushes  is  varied  with 
the  strength  of  the  field  current,  so  as  to  automatically  keep  the 
spark  of  the  proper  length,  which  should  be  about  J"  for  light 
load,  to  |"  for  full  load. 

In  order  that  a  Brush  generator   may  run  well  it   is   necessary 
that  the  brushes   be  properly  set.     The  brushes    should  project 


HANDBOOK    ON   ENGINEERING.  Ill 

from  the  holder  about  5^",  and  all  the  sets  should  be  in  line. 
They  can  be  brought  into  line  by  setting  those  at  one  end  first, 
then  rotate  the  rocker  until  the  end  of  the  brush  is  on  a  line  with 
the  end  of  a  copper  segment,  as  shown  in  Fig.  99.  Then  set 
the  brush  at  the  other  end  of  the  commutator  so  as  to  come  in 
line  with  the  end  of  the  copper  segment,  the  same  as  the  first 
one.  The  other  brushes  can  be  brought  into  line  by  using 
a  hard  wood  straight  edge.  The  two  sets  of  brushes  must  be 
placed  90  degrees  apart,  which  can  be  accomplished  by  setting 
them  to  the  edges  of  the  copper  segments  following  each  other, 
as  is  clearly  shown  in  Fig.  99. 

The  brushes  should  be  set  so  that  they  bear  on  the  commuta- 
tor at  the  end  and  for  a  distance  of  about  J"  back.  If  they  are 
too  long  they  will  not  bear  t-t  the  end  and  will  thus  increase  the 
sparking,  and  if  too  short  they  will  drop  unto  the  commutator 
slots  and  injure  the  copper  tips. 

The  commutator  should  be  cleaned  off  with  fine  sand  paper 
every  day  as  soon  after  stopping  as  possible.  To  keep  the  seg- 
ments all  even  and  true,  the  sand  paper  can  be  placed  around  a 
stick  planed  true  and  held  against  the  commutator  while  it  is 
running.  It  is  better  to  remove  the  brushes,  when  polishing  the 
commutator,  and  make  sure  that  the  current  is  open. 

As  the  current  of  these  machines  is  of  very  high  voltage,  they 
must  be  handled  with  great  care,  to  avoid  injury.  A  rubber  mat 
should  be  provided  for  the  attendant  to  stand  upon,  and  no  one 
should  ever  touch  any  part  of  the  machine  if  not  standing  on 
rubber,  or  thoroughly  dry  wood,  known  by  trial  to  be  a  safe  in- 
sulator. Only  one  hand  should  be  used  in  handling  any  part  of 
the  machine,  unless  it  is  not  running.  It  is  a  good  idea  to  use 
rubber  gloves  when  working  around  these  machines. 


HANDBOOK    ON    ENGINEERING. 


CHAPTER   X. 

THE  ALTERNATING  CURRENT  SERIES  ARC  LIGHTING 
SYSTEM. 

In  alternating  current  arc  lighting  systems  of  the  series  type, 
a  special  type  of  transformer  is  used,  which  is  commonly  called  a 
regulating  transformer,  or  a  constant  current  transformer.  The 
general  principles^  and  the  operation  of  transformers  is  fully  ex- 
plained in  the  section  on  alternating  currents.  In  this  connection 
it  will  be  sufficient  to  say  that  in  alternating  current  systems,  the 
currents  sent  out  from  the  central  station  are  of  a  much  higher 
voltage  than  is  required  to  operate  the  lamps  or  other  apparatus 
in  which  the  current  is  used.  This  high  primary  current  voltage 
is  used  so  as  to  be  able  to  transmit  a  large  amount  of  energy  with 
wires  of  small  size.  At  the  receiving  end  of  the  line  the  current 
is  passed  through  transformers  that  generate  secondary  currents 
of  whatever  voltage  may  be  required.  For  the  operation  of  in- 
candescent lamps,  motors  and  other  devices,  constant  potential 
currents  are  necessary ;  that  is,  currents  that  keep  the  voltage 
constant  but  change  the  strength,  or  amperes.  For  series  arc 
lighting  it  is  necessary  to  have  currents  that  are  just  the  opposite 
of  this ;  that  is,  the  amperes  remain  constant,  but  the  volts  in- 
crease and  decrease  as  the  number  of  lamps  increase  and  de- 
crease. A  transformer  acting  in  its  natural  way  will  develop  a 
constant  potential  secondary  current ;  therefore,  to  make  it  de- 
velop a  constant  current  with  variable  potential,  it  is  necessary 
to  resort  to  mechanical  means. 


HANDBOOK    ON   ENGINEERING. 


113 


The  way  in  which   transformers  are  arranged  so  as  to  develop 
constant  currents  is  very  simple  as  well  as  effective,  it  consists 


Fig.  100.    Constant  Current  Transformer  for  General  Electric 
Series  Alternating  Arc  Lighting  System. 

merely  in  constructing  the  transformer  so  that  one  of  the  coils 
may  be  moved  close  up  or  far  away  from  the  other.  If  the  two 
coils,  primary  and  secondary,  are  close  together,  the  effect  of  the 
primary  upon  the  secondary  will  be  much  greater  than  if  they  are 
far  apart ;  hence,  when  close  together  the  voltage  generated  in 
the  secondary  will  be  high,  and  when  far  apart  the  voltage  of  the 
secondary  will  be  low.  From  this  it  will  be  seen  that  to  make  a 
transformer  so  that  it  will  regulate  the  voltage  in  proper  propor- 
tion for  any  number  of  lamps  in  the  circuit,  all  that  is  necessary 
is  that  the  distance  between  the  coils  be  varied  in  a  manner  to 
agree  with  the  variation  in  the  number  of  lamps, 

8 


114 


HANDBOOK    ON    ENGINEERING. 


THE    GENERAL    ELECTRIC    CONSTANT    CURRENT 
TRANSFORMER. 

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HANDBOOK    ON    ENGINEERING.  115 

lished  can  be  made  clear  by  means  of  Fig.  100,  which  shows  a 
General  Electric  Regulating  transformer  with  the  outer  casing  re- 
moved.    Looking  at  this  illustration  it  will  be  seen  that  there  is  a 
rocking  lever,  which  carries  at  one  end  a  weight,  while  to   the 
other  end  the  upper  coil  of  the  transformer  is  attached.     The  ob- 
ject of  the  weight  is  to  balance  the  coil  so  that  a  very  small  up- 
ward force  will  move  the  latter  upward.     Generally,  the  lower, 
stationary  coil  is  the  primary,  and  the  upper,  movable  coil,  is  the 
secondary,     The  currents  flowing  in  these  two  coils  repel  each 
other,  in  the  same  way  that  magnet  poles  of  the  same  polarity  re- 
pel each  other.     If  the  current  in   the  secondary  becomes  too 
strong,    the  repelling   force   is   increased,  and  the  upper  coil  is 
raised.     The  raising  of  this  coil  causes   the   current  to  reduce, 
because  the  further  apart  the  coils  are  the  weaker  the  inductive 
action  of  the  primary  upon  the  secondary.     If  the  current  in  the 
secondary  becomes   too  weak  the  upward   push  will  be  reduced 
and   the   coils   will   come  closer  together,    and   as   a  result  the 
secondary  current  will  be  increased.     In  either  case  the  change  in 
the  position  of  the  secondary  coil  will  have  the  effect  of  returning 
the  current  in  the  secondary  to  the  proper  strength ;  that  is,  if  it 
is  too  strong  it  will  be  reduced,  and  if  it  is  too  weak  it  will  be  in- 
creased.    The  counterbalance  weight  is  so  proportioned  that  the 
excess  of  weight  in  the  movable  coil  is  just  enough  to  balance  the 
upward  push  of  the  current  when   the  latter  is  of  the    proper 
strength.     This  being  the  case,  it  can  be  seen  that  if  the  rocking 
beam  is  mounted  so  as  to  swing  freely,  and  the  transformer  is  set 
so  that  the  coil  will  not  rub  against  the  iron  core,  the  apparatus 
will  respond  to  very  small  changes  in  the  strength  of  the  current. 
This  apparatus,  like  a  steam  engine  governor,  can  be  made  so  as 
to  be  sensitive,  and  if  too  sensitive,  it  will  have  a  pumping  ac- 
tion, that  is,  the  rocking  beam  will  acquire  a  see-saw  movement, 
and  the  current  will  increase  and  decrease  in  time  with  the  move- 
ment, thus  causing  the  lamps  to  bum  unsteady      The  manufac- 


116 


HANDBOOK   ON    ENGINEERING. 


turers,  by  actual  trial  adjust  the  weight  to  the  point  that  will  give 
the  closest  regulation  without  causing  a  pumping  action. 

These  regulating  transformers  are  made  in  many  sizes,  the 
General  Electric  Company  make  them  from  6  to  100  lamp  capac- 
ity. The  smaller  sizes  are  constructed  so  as  to  be  cooled  by  the 
currents  of  air  that  naturally  circulate  through  them.  The  larger 


A  B 

Fig.  102.    Front  and  Back  Yiews  of  Switchboard  Shown 
in  Diagram  Fig.  101, 

sizes  are  provided  with  a  tight  casing  which  is  filled  with  oil, 
this  construction  being  used  so  as  to  cool  off  the  coils  more 
thoroughly  than  they  would  be  with  air.  If  the  transformer  is  of 
the  air  cooled  type,  a  dash  pot  is  generally  provided  to  prevent 
the  movable  coil  from  moving  too  rapidly  when  a  large  number  of 


HANDBOOK    ON   ENGINEERING. 


117 


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HANDBOOK    ON    ENGINEERING. 


lamps  are  cut  in  or  out  of  the  circuit  at  a  time.  The  oil  cooled 
transformers  do  not  require  a  dash  pot  because  the  oil  retards 
the  movement  of  the  coil. 

From  Fig.  101,  the  way   in   which    a   regulating  transformer, 
such  as  shown  in  Fig.  100,  is  connected  with  the  primary  circuit. 


Fig.  104.  Front,  Back  and  Side  Yiews  of  Switchboard 
Shown  in  Diagram  Fig.  108. 

and  with  the  lamp  circuit,  can  be  easily  understood.  At  G  is  a 
wiring  diagram  showing  all  the  connections,  and  A  and  B  show 
in  outline,  the  front  and  side  view  of  the  switchboard.  As  the 
explanatory  notes  on  these  diagrams  are  complete,  no  further  ex- 
planation will  be  necessary. 


HANDBOOK    ON    ENGINEERING. 


119 


Fig.  102  gives  photographic  views  of  the  front  and  back  of  the 
switchboard,  respectively. 


Fig.    105.  Westinghouse  Constant  Current  Transformer  for 
Series  Alternating  Arc  Lighting. 


Fig.  106.  Front,  Back  and  Side  Views  of  Switchboard  used  with 
Westinghouse  Series  Alternating  Arc  Lighting  System. 


120  HANDBOOK    ON    ENGINEERING. 

The  diagram  (7,  Fig.  101,  shows  the  circuit  connections  for  a 
small  size  transformer  feeding  into  a  single  lamp  circuit,  but 
large  transformers  are  commonly  arranged  so  as  to  feed  into  two 
lamp  circuits.  Fig.  103  shows  the  outline  A,  of  the  front,  and 
JB,  of  the  side  of  a  switchboard,  for  a  large  transformer  feeding 
into  two  lamp  circuits,  and  the  wiring  diagram  C.  The  front,  side 
and  back  of  this  switchboard  are  shown  in  Fig.  104. 
THE  WESTINQHOUSE  CONSTANT  CURRENT  TRANSFORMER. 

Fig.  JOS  is  a  photographic  view  of  the  regulating  transformer 
made  by  the  Westinghouse  Company.  There  is  some  difference 
in  the  details  of  construction  between  this  transformer,  and  the 
one  shown  in  Fig.  100,  but  the  principle  of  action  is  the  same. 
In  this  design,  there  are  two  movable  coils  instead  of  one,  and 
the  stationary  coil  is  secured  between  them.  The  counterbalanc- 
ing weights  are  connected  with  the  movable  coils  through  chains 
that  run  over  large  sheaves,  each  coil  being  independently  coun- 
terbalanced, as  it  must  be,  for  in  this  arrangement,  when  the 
upper  coil  rises,  the  top  one  will  move  down.  The  two  coils, 
however,  can  be  connected  with  separate  lamp  circuits,  and  then 
each  one  will  move  according  to  the  demands  of  its  circuit,  and 
without  reference  to  the  movement  of  the  other. 

Fig.  106  is  a  photographic  view  of  the  front  and  back  of  the 
Westinghouse  switchboard,  used  in  connection  with  the  regulat- 
ing transformers.  The  transformer  Fig.  105,  is  of  the  oil  cooled 
type,  and  of  100  lamp  capacity.  With  the  air  cooled  transform- 
ers this  company  provide  a  dash  pot  that  is  constructed  with  a 
valve  that  retards  the  movement  of  the  coils  when  they  come  to- 
gether, more  than  when  they  separate,  so  that  the  current  may 
not  increase  in  strength  too  rapidly. 

REACTANCE  COIL  CONSTANT  ALTERNATING  CURRENT 
REGULATORS. 

The  General  Electric  and  the  Westinghouse,  regulating  trans- 
formers, are  transformers  arranged  so  as  to  generate  a  secondary 


HANDBOOK    ON   ENGINEERING.  121 

current  of  constant  strength  and  variable  voltage,  by  being  so 
constructed  that  the  distance  between  the  primary  and  sec- 
ondary coils  may  be  varied,  being  increased  to  lower  the  voltage 
and  reduced  to  increase  it.  There  is  another  way  in  which  a 
constant  secondary  current  can  be  obtained,  and  this  consists  in 
using  what  is  commonly  called  a  choke  coil  or  reactance  coil,  and 
arranging  this  so  that  its  choking  effect  may  be  varied  automati- 
cally as  the  voltage  required  varies.  To  make  clear  the  action  of 
choking  coils  it  will  be  necessary  to  say  that  when  an  alternating 
current  passes  through  a  coil  of  wire,  it  reacts  upon  itself,  that  is, 
it  tends  to  generate  a  current  flowing  in  the  opposite  direction. 
It  cannot  generate  such  a  current,  but  it  can  develop  a  back 
pressure  or  e.  m.  f.  and  this  will  reduce  the  flow  of  current.  If 
the  coil  of  wire  is  wound  upon  paper  tube,  the  choking  action 
will  be  very  much  less  than  it  will  be  if  a  core  made  of  finely  lam- 
inated iron  is  inserted  within  the  tube.  With  a  little  reflection  it 
can  be  seen  that  with  this  difference  existing  between  the  effect 
of  a  core  of  iron  and  no  core,  the  choking  action  can  be  varied 
by  providing  an  iron  core  that  can  be  drawn  in  or  out  of  the  coil. 

THE  WESTERN  ELECTRIC  REGULATOR  FOR  CONSTANT 
ALTERNATING  CURRENTS. 

The  Western  Electric  Company  make  a  regulator  for  series  al- 
ternating arc  lighting  that  operates  on  the  principle  explained  in 
the  foregoing.  A  side  view  of  this  regulator  is  shown  in  Fig. 
107.  The  wire  coil  is  suspended  from  one  end  of  a  rocking  beam 
which  carries  at  its  other  end  a  counter-balancing  weight.  This 
coil  with  the  iron  core  and  the  side  pieces  constitutes  what  is 
commonly  called  a  solenoid  magnet.  Such  magnets  exert  a  pull 
upon  the  iron  core  when  a  current  passes  through  the  coil,  and 
the  magnitude  of  the  pull  increases  with  the  strength  of  the  cur- 
rent. From  this  it  will  be  seen  that  when  current  passes  through 
the  coil  of  Fig.  107,  the  pull  exerted  draws  it  upward,  the 


122  HANDBOOK    ON    ENGINEERING. 

stronger  the  current  the  higher  the  position  to  which  the  coil  is 
drawn.  Now  the  choking  action  of  the  coil  will  increase  as  the 
uoil  is  raised,  because  more  of  the  iron  core  will  be  within  it. 
The  choking  action  reduces  the  strength  of  the  current ;  there- 
fore, as  the  coil  is  raised  by  the  increased  pull  due  to  the  in- 
creased current,  the  choking  action  is  increased,  and  the  increase 
in  current  strength  is  checked.  By  properly  adjusting  the 


• 

Fig.  107.    Western  Electric  Regulator  for  Constant  Current 
Series  Alternating  Arc  Lighting  System. 

counterbalancing  weight,  the  apparatus  can  be  made  so  that  a 
very  small  increase  in  current  strength  will  move  the  coil  up  to 
its  highest  position,  and  as  it  only  requires  a  small  movement  of 
the  coil  to  effect  a  considerable  change  in  the  strength  of  the  cur- 
rent, it  can  be  seen  that  the  regulating  action  can  be  made  very 
accurate.  It  is  said  that  these  regulators  will  respond  to  a  vari- 
ation of  one-tenth  of  an  ampere  in  the  current  strength,  when 
Carefully  adjusted. 


HANDBOOK  ON  ENGINEERING.  123 

THE  ADAMS-BEGNALL  REGULATOR  FOR  CONSTANT 
ALTERNATING  CURRENTS. 

Fig>  108  shows  another  choke  coil  regulator  made  by  the 
Adams-Begnall  Electric  Company.  Comparing  this  illustration 
with  Fig.  107  it  will  be  seen  that  while  the  principle  of  operation 
is  the  same,  there  is  a  considerable  difference  in  the  design.  An 
important  feature  about  this  regulator  is  the  arrangement  of  the 
dash  pot.  It  is  found  in  practice  that  the  retarding  action  of  the 


Fig.  108.    Adams-Begnall  Regulator  for  Constant  Current 
Series  Alternating  Arc  Lighting  Systems. 

dash  pot  is  not  required  to  correct  small  changes  in  the  strength 
of  current,  because  such  changes  are  corrected  by  a  very  small 
movement  of  the  coil,  so  that  in  such  cases  the  dash  pot  is  really 
objectionable.  When,  however,  a  large  number  of  lamps  are 
cut  in  or  out  of  the  circuit  at  one  time,  there  is  a  tendency  to 
greatly  increase  or  decrease  the  current,  and  then  the  coil  must 


124  HANDBOOK    ON    ENGINEERING. 

move  over  a  considerable  distance  to  keep  the  current  constant. 
If  the  coil  moves  over  a  long  distance  it  will  acquire  a  velocity 
that  will  carry  it  beyond  the  mark,  and  thus  over  regulate,  unless 
its  motion  is  retarded;  hence,  the  dash  pot  is  desirable  to  con- 
trol the  movement  of  the  coil  when  it  has  to  move  over  long  dis- 
tances, but  not  for  short  distances.  In  the  regulator  Fig.  108 
this  result  is  accomplished  by  providing  a  certain  amount  of  lost 
motion  in  the  connections  between  the  coil  and  the  dash  pot  rod, 
so  that  the  coil  has  to  move  through  some  distance  to  take  up 
the  slack  in  these  connections  before  the  dash  pot  plunger  is 
moved.  This  last  motion  is  sufficient  to  cover  the  range  of  reg- 
ulation over  which  the  best  results  are  obtained  when  the  coil 
moves  freely. 

THE  FORT  WAYNE  REGULATOR  FOR  CONSTANT 
ALTERNATING  CURRENTS. 

Fig.  J09  is  a  side  view   of   the   regulator  made   by   the   Fort 
Wayne  Electric  Works.     This  regulator,   like   the   two  last  de- 


Fig.  109.    Fort  Wayne  Regulator  for  Constant  Current  Series 
Alternating  Arc  Lighting  System. 

scribed,  is  of  the  choke  coil,  or  reactance  coil  type.  The  dis- 
tinctive feature  of  this  regulator  is  that  the  iron  core,  as  well  as 
the  wire  coil  are  made  movable,  and  when  the  latter  moves  up, 


HANDBOOK    ON    ENGINEERING. 


125 


the  core  moves  down.     The    two   parts  are    suspended   from  the 
opposite  ends  of  rocking  levers,  the    distances   from  the   point  of 


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support  to  the  ends  being  properly  proportioned  so   that  the  core 


126  HANDBOOK    ON    ENGINEERING. 

balances  the  coil,  thus  making  the  former  take  the  place  of  the 
counterbalancing  weight  in  Fig.  107  and  108. 

With  the  choke  coil,  or  reactance  type  of  regulator,  the  arc 
light  circuit  can  be  connected  directly  with  the  primary  alterna- 
ting current  mains,  if  the  voltage  of  the  latter  is  high  enough. 
In  cases  where  the  primary  voltage  is  too  low,  an  ordinary  step 
up  transformer  is  used  to  generate  a  secondary  current  of  the 
proper  voltage. 

The  following  wiring  diagrams,  which  show  the  way  in  which 
the  Fort  Wayne  apparatus  is  connected  in  the  circuit,  will 
serve  to  illustrate  the  general  arrangement  of  all  types  of  react- 
ance coil  regulators,  as  the  difference  between  them  is  in  the 
details,  and  not  in  the  general  principle  of  operation. 

Diagram  A  of  Fig.  110  shows  the  connections  between  the  bus 
bars  of  the  primary  circuit,  and  the  arc  lamp  circuit  for  the 
Fort  Wayne  system  when  no  step-up  transformer  is  used.  This 
arrangement  is  possible  if  the  primary  voltage  is  1100  or  2200. 
With  the  former  voltage  an  arc  lamp  circuit  with  12  lamps  can 
be  operated,  and  with  the  2200  volts  25  lamps  can  be  used.  For 
a  greater  number  of  lamps,  a  step-up  transformer  is  required. 
As  a  rule,  it  is  considered  preferable  to  use  a  transformer  in  all 
cases,  whether  the  primary  voltage  is  high  enough  or  not,  as  by 
this  arrangement  the  lamp  circuit  is  completely  isolated  from  the 
main  line. 

In  this  diagram  the  regulator  is  shown  with  the  coil  and  core 
in  the  position  they  assume  when  the  lamp  circuit  is  short  cir- 
cuited, when  the  circuit  is  first  connected  with  the  main  line  bus 
bars,  this  is  not  the  position  of  the  regulator,  in  fact  the  coil  is  in 
the  bottom  or  full  load  position.  On  this  account  a  special  re- 
actance coil  is  provided,  as  shown  in  the  diagram,  the  office  of 
which  is  to  hold  back  the  current,  momentarily,  until  the  regu- 
lator assumes  its  proper  position.  When  the  starting  switch  is 
closed  this  coil  is  cut  out. 


HANDBOOK    ON    ENGINEERING.  127 

Diagram  B,  Fig.  110,  is  a  more  elaborate  arrangement  which 
shows  the  connections  when  a  step-up  transformer  is  used,  and 
in  addition  includes  a  watt  meter,  a  potential  transformer  for  the 
latter,  and  a  current  transformer  for  the  ammeter.  These  two 
last  named  transformers  are  provided  simply  to  obtain  currents 
of  the  proper  voltage  and  strength  for  the  instruments  they 
actuate. 

The  operation  of  starting  a  Fort  Wayne  arc  lamp  circuit  is  as 
follows :  — Looking  at  diagram  J.,  Fig  110,  the  first  operation  is 
to  close  the  plug  switches  that  connect  with  the  primary  bus  bars. 
This  being  done  the  current  will  flow  from  the  upper  bus  bar 
through  the  regulator,  the  reactance  coil  and  the  lower  part  of 
the  starting  switch,  back  to  the  lower  bus  bar.  The  current  pas- 
sing through  the  regulator  will  at  once  move  it  to  the  no  load 
position,  so  that  if  now  the  starting  cwitch  is  moved  to  the  posi- 
tion that  short  circuits  the  reactance  coil,  no  damage  will  be 
done,  as  the  regulator  will  be  in  position  to  check  the 
flow  of  current.  During  this  time  the  lamp  circuit  has  been 
short  circuited  through  the  lower  connection  of  the  starting 
switch,  but  the  final  movement  of  this  switch  opens  the  lamp 
circuit.  The  explanation  of  diagram  jB,  Fig0  110,  is  the  same  as 
the  foregoing,  for  as  will  be  seen  the  introduction  of  the  step-up 
transformer  does  not  alter  the  switching  arrangements. 

ALTERNATING  CURRENT  ENCLOSED  ARC  LAMPS  FOR  CON- 
STANT CURRENT  SERIES  CIRCUITS. 

Alternating  current  arc  lamps  for  series  circuits  are  of  the 
differential  type.  They  are  manufactured  by  the  large  companies 
and  by  many  small  concerns.  All  of  them  are  practically  the 
same  in  principle  of  operation,  being  provided  with  a  clutch  act- 
ing directly  upon  the  carbon,  and  mechanism  to  actuate  the 
clutch. 

The  lamp  of  this  type  made  by  the  General  Electric  Company 


128 


HANDBOOK    ON    ENGINEERING. 


is  illustrated  in  Fig.  Ill  A  showing  the  external  appearance, 
and  B  the  actual  mechanism.  The  way  in  which  the  lamp  oper- 
ates can  be  understood  from  the  diagram  (7,  which  shows  the 
parts  in  the  position  they  assume  when  the  current  is  turned  off. 
The  switch  at  the  upper  right  hand  corner  short  circuits  the  lamp, 
making  a  direct  connection  from  one  binding  post  to  the  other. 
When  this  switch  is  opened,  the  current  first  passes  through  the 


Fig.  111.    General  Electric  Enclosed  Arc  Lamp  for 
Series  Alternating  Current  Circuits. 


HANDBOOK   ON   ENGINEERING.  129 

but  as  the  carbons  burn  away,  the  increased  length  of  the  arc  will 
cause  the  current  through  the  shunt  magnet  to  increase,  thus  in- 
creasing the  pull  of  the  latter.  As  the  shunt  magnet  gradually 
strengthens,  it  gradually  pulls  up  its  end  of  A  thereby  bringing 
the  carbons  closer  together,  and  when  A  has  been  lowered  enough 
at  its  left  hand  end,  the  clutch  strikes  the  stop  and  permits  the 
carbon  to  slip  through.  If  the  carbon  should  fail  to  feed,  or  the 
circuit  through  the  lamp  should  open  through  any  cause,  the 
shunt  magnet  will  become  strong  enough  to  pull  up  its  end  of  A 
until  the  cut  out  switch  is  closed. 

In  this  lamp  as  shown  in  this  diagram,  the  upper  carbon  holder 
slides  within  a  tube  and  connection  between  it  and  the  wire  lead- 
ing from  the  series  magnet  is  made  through  a  flexible  cable.  The 
General  Electric  Company  also  makes  lamps  in  which  the  upper 
carbon  holder  is  attached  to  a  cross-head  that  slides  between  two 
parallel  rods,  but  the  method  of  conveying  the  current  to  the 
upper  carbon  remains  the  same,  that  is,  by  a  flexible  cable. 

The  adjusting  weight  on  A  is  for  the  purpose  of  adjusting 
the  lamp  so  as  to  operate  with  more  or  less  current.  If  the 
weight  is  moved  toward  the  clutch  rod  end,  the  arc  is  short- 
ened and  the  voltage  lowered.  Movement  in  the  opposite  di- 
rection produces  the  opposite  effect.  A  dash  pot,  shown 
at  D,  is  provided  to  prevent  too  violent  movement  of  the 
clutch  lever  A. 

THE    WESTINGHOUSE    ALTERNATING    CURRENT  LAMP  FOR 
CONSTANT    CURRENT  SERIES  CIRCUITS. 

The  external  appearance  of  the  Westinghouse  enclosed  lamp 
is  shown  at  A  in  Fig.  112,  the  mechanism  of  the  constant  cur- 
rent series  type  is  shown  at  B,  and  a  diagramatic  representation 
of  the  latter  is  given  in  (7.  It  will  be  seen  from  this  diagram 
that  this  lamp  has  all  the  parts  shown  in  Fig.  Ill,  although  they 

9 


130 


HANDBOOK    ON    ENGINEERING. 


differ  considerably  in  form  and  are  not  in  the  same  position.  The 
series  and  shunt  magnets  act  upon  the  opposite  ends  of  lever  A, 
and  an  adjusting  weight  is  provided  to  regulate  the  length  of  the 
arc.  The  cut-out  switch,  although  differently  located,  is  actuated 
in  the  same  mariner.  The  upper  carbon  holder  slides  within  a 
tube  and  connection  is  made  with  it  through  a  flexible  cable. 
In  the  General  Electric  lamp  the  tube  is  slotted,  and  an  ex- 


Fig.  112.    Westinghouse  Enclosed  Arc  Lamp  for  Series 
Alternating  Current  Circuits. 

• 
tension  from  the  upper  carbon  holder  passes  through  this   slot  and 

connects  with  the  cable.  In  the  Westinghouse  lamp  the  cable  is 
attached  to  the  top  of  the  carbon  holder  and  runs  up  within  the 
tube  to  the  upper  end  where  it  is  secured. 


HANDBOOK    ON    ENGINEERING. 


131 


THE  FORT  WAYNE    ALTERNATING  CURRENT  ENCLOSED 

LAMPS. 

The  external  appearance  of  a  Fort  Wayne  "Wood"  enclosed 
arc  lamp  is  shown  at  A  in  Fig.  113,  and  the  mechanism  of  the 
lamp  for  series  alternating  current  circuits  is  shown  at  B.  Al- 
though there  is  a  considerable  difference  in  the  design  of  the 


Type  Sa  Lamp 
Form  C 


B 


Figr.  113.    Fort  Wayne  "Wood"  Enclosed  Arc  Lamp  for 
Series  Alternating  Current  Circuits. 

mechanism,  the  principle  of  operation  is  the  same  as  in  the  lamps 
already  described,  so  that  in  so  far  as  the  electrical  connections 
are  concerned  it  could  be  represented  diagram atically  by  either 
of  the  two  diagrams  shown  in  connection  with  Figs.  Ill  and  112. 
ID  the  design  of  the  mechanism  the  most  important  differences  are  in 


132 


HANDBOOK    ON    ENGINEERING. 


the  arrangement  of  the  magnets,  and  in  the  means  for  conveying 
current  to  the  upper  carbon  holder.  The  magnets  instead  of  be- 
ing placed  side  by  side  at  the  top  of  the  lamp  are  set  one  above 
the  other,  and  they  act  upon  an  armature  made  in  the  form  of  a 
letter  H.  There  are  two  series  *coils  and  two  shunt  coils,  the  for- 
mer being  at  the  top  and  surrounding  the  upper  legs  of  the  arma- 
ture, while  the  latter  are  at  the  bottom  and  surround  the  lower 


A  B  C 

Fig.  114.    Western  Electric  Enclosed  Arc  Lamp  for  Series 
Alternating  Current  Circuits. 

legs  of  the  armature.  The  long  coil  seen  at  the  left  of  the  lamp 
is  the  starting  resistance.  The  connection  with  the  upper  carbon 
holder  is  made  by  providing  the  fatter  with  contacts  made  in  the 
form  of  springs,  that  rub  against  the  inner  surface  of  the  tube 
within  which  the  holder  slides. 

The  appearance  of  the  Western  Electric  Company's  enclosed 
arc  lamp  is  shown  at  A  in  Fig.  114.     The  mechanism  for  the  se- 


HANDBOOK    ON    ENGINEERING. 


133 


ries  alternating  current  type  is  shown  at  .Band  (7,  the  first  illus- 
tration being  a  side  view  of  the  mechanism,  and  the  second  a 
front  view.  This  lamp  is  provided  with  double  coil  magnets,  and, 
as  will  be  seen,  they  pull  down  on  the  lever  that  actuates  the 
clutch  rod.  The  coil  located  at  the  top  of  the  lamp,  is  the  start- 
ing resistance.  The  tube  within  which  the  upper  carbon  holder 
slides  is  of  rectangular  form  and  so  is  the  upper  end  of  the  car- 


B 


Fig.  115.    Types  of  Clutches  Used  in  Enclosed  Arc  Lamps. 

bon  holder.  Connection  with  the  circuit  is  made  through  a  cop- 
per ribbon  which  is  bent  in  zig-zag  fashion  so  as  to  compress 
when  the  carbon  holder  is  pushed  up  and  extend  when  it  drops 
down  as  the  carbon  is  consumed. 

The  construction  of  enclosed  lamps  is  so  simple  that  there  are 
but  few  details  that  require  special  explanation,  since  all  the 
working  parts  are  well  shown  in  the  illustrations  already  pre- 
sented. The  clutch  is  made  in  every  case,  so  as  to  grip  directly 


134  HLNDBOOK   ON    ENGINEERING. 

upon  the  carbon,  instead  of  upon  a  carbon  rod.  as  is  the  case 
.with  open  arc  lamps.  For  the  latter  type  of  lamp  a  clutch  acting 
on  the  carbon  directly  would  not  give  satisfactory  results  owing 
to  the  fact  that  the  arc  is  very  short,  but  in  the  enclosed  arc 
lamps  the  arc  is  about  three  times  as  long,  hence,  such  accuracy 
of  movement  in  feeding  the  carbons  down  is  not  required. 

Fig*  \15  shows  three  types  of  clutches,  A  being  the  design 
used  by  the  Western  Electric  Company,  B  the  design  of  the  Fort 
Wayne  Electric  Works,  and  C  the  design  of  the  Westinghouse 
Company. 

The  Western  Electric  Clutch  is  of  the  type  called  double 
clutch,  and  as  can  be  easily  seen  consists  of  two  clamping  rings, 
the  lower  one  being  held  up  by  the  top  one.  When  the  carbon 
feeds  down  the  lower  ring  strikes  the  stop  and  as  soon  as  it  set- 
tles sufficiently  to  release  its  hold,  the  carbon  slips  through. 
This  shortens  the  arc  and  strengthens  the  shunt  magnets  so  that 
they  draw  up  their  end  of  the  clutch  lever  and  prevent  further 
feeding  of  the  carbon . 

The  Fort  Wayne  clutch,  shown  at  B,  consists  of  a  sleeve  to 
which  a  clamping  lever  is  connected.  The  whole  device  is  held 
by  this  lever  so  that  it  clamps  the  carbon  until  the  sleeve  has 
moved  so  far  down  as  to  rest  on  the  stop  and  permit  the  lifting 
end  of  the  lever  to  drop  far  enough  to  release  the  rod. 

The  Western  Electric  and  the  Fort  Wayne  clutches  are  made 
wholly  of  metal,  and  in  fact  most  clutches  are  so  made.  The 
Westinghouse  Company,  however,  use  a  clutch  which  is  made  of 
a  porcelain  centre  and  a  metallic  supporting  band,  as  is  well  shown 
at  (7.  The  porcelain  ring  is  the  clutch  proper,  and  the  metallic 
band  is  provided  simply  to  hold  it.  This  band  is  made  with 
clinching  points  on  both  sides  so  as  to  hold  the  ring  firmly.  The 
object  of  using  a  porcelain  ring  is  to  prevent  current  from  pass- 
ing through  the  clutch  to  the  carbon.  If  the  clutch  is  made  of 
metal  there  is  a  remote  possibility  of  current  passing  through  it, 


HANBBOOK    ON    ENGINEERING. 


135 


and  if  it  should,  in  sufficient  quantity,  the  carbon  might  be 
burned  away  so  as  to  form  a  depression  into  which  the  clutch 
could  drop  and  thus  prevent  the  lamp  from  feeding. 

In  Fig.  \\6,  are  shown  the  Fort  Wayne  upper  carbon  holder 
at  A,  the  Western  Electric  upper  carbon  holder  at  B,  and  at  C 
the  square  tube  within  which  this  holder  slides,  together  with  the 


B 


Fig.  116.    Upper  Carbon  Holders  Used  with  Enclosed  Arc  Lamps. 

copper  ribbon  that  conveys  the  current  from  the  upper  end  of  the 
tube  to  the  top  of  the  carbon  holder. 

As  shown  in  the  foregoing,  the  General  Electric  and  the  West- 
jnghouse  lamps  are  made  so  as  to  convey  the  current  to  the  upper 
carbon  holder  through  a  cable,  and  this  construction  is  the  one 
most  generally  used  ;  the  two  arrangements  of  Fig.  116,  are,  how- 
ever, worthy  of  being  described  as  their  constructions  differ  from 


136  HANDBOOK   ON   ENGINEERING. 

each  other  and  from  general  usage.  The  Fort  Wayne  carbon 
holder  is  provided  with  collector  springs  at  its  upper  end,  and 
these  rub  against  the  under  surface  of  the  tube  into  which  the 
holder  and  carbon  telescope  when  the  latter  is  of  full  length.  As 
these  springs  slide  over  the  inner  surface  of  the  tube  they  keep  it 
bright j  and  also  maintain  their  own  contact  points  bright,  so  that 
a  good  electric  connection  is  always  insured. 

In  the  Western  Electric  upper  carbon  holder,  I?,  Fig.  116,  the 
upper  end  is  made  square,  so  as  to  prevent  it  from  turning,  while 
sliding  up  and  down  in  the  tube  C.  This  arrangement  is  neces- 
sary because  a  copper  ribbon  bent  in  zig-zag  fashion  is  placed  in- 
side the  tube,  and  one  end  is  secured  to  the  top  of  the  carbon 
holder,  while  the  other  end  is  fastened  to  the  top  of  the  tube.  If 
the  holder  could  twist  around,  it  would  soon  get  the  ribbon  in 
such  a  shape  that  it  would  bind  against  the  sides  of  the  tube  and 
prevent  the  carbon  from  moving  freely. 

DIRECT  CURRENT  ENCLOSED  ARC  LAHPS  OF  THE 
CONSTANT  POTENTIAL  TYPE. 

Enclosed  arc  lamps  are  used  extensively  at  the  present  time  on 
incandescent  lighting,  constant  potential  circuits,  direct  current 
and  alternating  current.  These  lamps  are  in  great  favor  for 
indoor  lighting,  owing  to  the  fact  that  they  operate  with  low 
voltage  currents  that  are  not  dangerous.  All  the  arc  lamp  man- 
ufacturers make  lamps  of  this  type. 

A  general  Electric  constant  potential  lamp  is  shown  in  Fig. 
117  at  A.  The  mechanism  is  seen  at  B  and  a  diagram  illustrat- 
ing the  principle  of  operation  is  given  at  C.  As  will  be  seen 
from  the  latter  figure,  the  construction  is  very  simple.  There  is 
but  one  set  of  magnet  coils,  and  these  pull  directly  upon  the  clutch 
rod.  The  construction  is  simple  because  the  principle  of  action 
makes  it  possible  to  use  simple  construction.  In  the  series  lamps 
described  in  the  foregoing,  it  is  necessary  to  have  magnet  coils 


HANDBOOK    ON    ENGINEERING. 


137 


connected  in  shunt  to  the  arc  as  well  as  coils  in  series  with  the 
arc.  This  arrangement  is  required  because  the  current  remains 
practically  constant,  hence,  the  pull  of  the  series  magnets  varies 
next  to  nothing ;  therefore,  these  magnet  coils  alone  cannot  cause 
the  upper  carbon  to  feed  down  as  the  arc  lengthens  out.  The 
shunt  magnet  coils,  however,  become  stronger  as  the  arc  becomes 
longer,  because  the  resistance  of  the  latter  is  increased,  hence, 
as  the  carbons  burn  away,  the  strength  of  the  shunt  magnet  in- 


General  Electric  Enclosed  Arc  Lamp  for  Constant 
Potential  Direct  Current  Circuits. 

creases  and  lifting  its  end  of  the  actuating  lever,  depresses  the 
clutch  rod,  causing  the  clutch  to  strike  the  stop  when  the  carbons 
have  burned  away  enough  to  require  feeding.  In  a  constant 
potential  lamp  the  current  weakens  as  the  arc  lengthens  and  thus 
the  pull  of  the  magnet  is  reduced.  As  the  length  of  the  arc 


138 


HANDBOOK   ON   ENGINEERING. 


gradually  increases,  the  magnet  pull  gradually  reduces,  so  that 
the  clutch  rod  slowly  descends  until  the  clutch  strikes  the  stop 
and  permits  the  carbon  to  slip  through.  The  long  coil  seen  on 


the  left  side  of  the  diagram  is  simply  a  resistance  used  to  balance 
the  portion  of  the  voltage  not  required  for  the  lamp.  These 
lamps  operate  with  a  voltage  of  about  75  to  80  and  as  the  cur- 
rent voltage  is  from  110  to  115,  a  resistance  has  to  be  used  to 


HANDBOOK   ON   ENGINEERING.  139 

balance  <the  extra  35  volts0  The  illustration  B  and  the  diagram 
C  show  clearly  the  upper  carbon  holder  and  the  way  in  which  it 
is  guided  between  parallel  rods ;  the  former  shows  the  way  in 
which  the  magnet  armature  is  connected  directly  with  the  clutch. 
In  the  diagram  G  it  will  be  seen  that  the  wire  from  the  P  binding 
post  is  connected  with  a  ring  midway  between  the  ends  of  the 
resistance  coil.  This  is  a  contact  ring  that  is  provided  so  that 
by  sliding  it  up  or  down  more  or  less  of  the  resistance  can  be  cut 
into  the  circuit.  When  the  ring  is  in  the  position  that  intro- 
duces the  proper  amount  of  resistance,  it  is  made  fast  so  that  it 
may  not  become  displaced  thereafter. 

THE  WESTINGHOUSE  CONSTANT  POTENTIAL  LAHP. 

Fig*  \  f  8  shows  the  mechanism  of  the  Westinghouse  constant 
potential  lamp  at  B.  In  this  design  the  balancing  resistance  is 
wound  upon  a  large  porcelain  spool  and  occupies  the  upper  part 
of  the  lamp  casing.  The  actuating  magnet  coils  are  directly 
below  it.  The  external  appearance  of  the  lamp  is  shown  at  A  in 
Fig.  118,  and  a  diagrammatic  representation  of  the  mechanism  and 
circuit  connections  is  given  at  C.  From  this  diagram  it  will  be 
seen  that  the  connections  with  the  circuit  are  the  same  as  in  the 
General  Electric  lamp.  The  portion  of  the  resistance  coil  that 
is  cut  into  the  circuit  is  adjusted  by  means  of  a  sliding  contact 
B  which  presses  against  the  surface  of  the  resistance  wire,  the 
latter  being  bare.  When  B  has  been  moved  to  the  proper  posi- 
tion the  screw  at  A  is  tightened  and  this  holds  B  in  position. 

THE  FORT  WAYNE  CONSTANT  POTENTIAL  LAMP. 

Fig.  U9  shows  the  mechanism  of  the  Fort  Wayne  constant 
potential  lamp  at  A.  The  first  impression  gained  from  looking 
at  this  illustration  is  that  the  construction  is  entirely  different  in 
principle  from  the  two  lamps  of  this  type  already  described; 
such,  however,  is  not  the  case.  The  apparent  difference  is  due 


140 


HANDBOOK    ON    ENGINEERING. 


to  the  fact  that  the  balancing,  or  steadying,  resistance" as  it  is 
also  called,  is  placed  in  the  separate  cylindrical  part  directly 
above  the  lamp.  In  the  wiring  connections  of  the  lamp  there 
is  a  difference  that  is  quite  noticeable.  In  the  diagram  B  it  will 
be  seen  that  in  addition  to  the  ordinary  balancing  resistance, 
shown  at  the  top  of  the  diagram,  there  are  two  resistances,  one 
for  regulating  the  strength  of  the  current  and  the  other  for  ad- 
justing the  voltage.  The  latter  resistance  is  in  reality  a  part  of 


steadying  resistance 


Fig.  119.    Fort  Wayne  Enclosed  Arc  Lamp  for  Constant 
Potential  Direct  Current  Circuits. 

the  steadying  resistance,  that  portion  that  has  to  be  cut  in  or  out 
of  the  circuit  to  obtain  the  proper  voltage  at  the  arc.  The  cur- 
rent adjusting  resistance,  however,  is  an  addition,  and  is  for  the 
purpose  of  adjusting  the  lamp  for  different  strengths  of  current. 
The  normal  current  is  5  amperes,  but  by  means  of  the  current 


HANDBOOK    ON    ENGINEERING. 


141 


adjusting  resistance  it  may  be  reduced  or  increased  considerably, 
one  ampere  about.  The  reduced  current  will  give  less  light  and 
the  increased  current  more  light  with  the  same  voltage. 

DIRECT  CURRENT  ENCLOSED  LAMPS  FOR  OPERATION  ON 
POWER  CIRCUITS,  MULTIPLE  SERIES  SYSTEM. 

The  lamps  described  in  the  preceding  section  are  used  on  in- 
candescent Mghting  circuits  of  110  to  125  volts,    and   each  lamp 


A  B  C 

Fig.  120.    Fort  Wayne  Multiple  Series  System  Lamp  for  Op- 
eration on  Power  Circuits  Direct  Current. 

is  connected  directly  across  the  line,  just  the  same  as  incan- 
descent lamps  are.  Enclosed  arc  lamps  are  also  used  on  220  and 
500  volt  circuits.  With  the  first  named  voltage  they  are  con- 
nected two  in  "series,  and  with  the  second,  five  in  series.  Lamps 
Of  this  type,  which  we  will  describe  in  this  section  are  called 


142  HANDBOOK    ON    ENGINEERING. 

"  Multiple  series  lamps.  "  The  mechanism  of  these  lamps  is 
somewhat  different  from  that  of  the  simple  constant  potential 
lamps  used  on  110  volt  incandescent  lighting  circuits,  and  in  the 
case  of  most  manufacturers  the  external  appearance  is  slightly 
modified.  The  external  appearance  of  the  Fort  Wayne  lamp  of 
this  type  is  shown  at  A  in  Fig.  120.  By  comparing  it  with  Fig. 
119  it  will  be  seen  that  the  resistance  drum  on  top  of  the  lamp 
proper  is  considerably  longer.  A  comparison  between  the  me- 
chanism of  the  two  lamps  will  at  once  reveal  the  fact  that  in  internal 
construction  there  is  quite  a  difference.  The  arrangement  and 
operation  of  this  mechanism  can  be  clearly  understood  from  the 
diagrammatic  representation  of  it  at  C  in  Fig.  120.  Looking  at 
this  diagram  it  will  be  seen  that  there  are  two  magnets,  a  series 
and  a  shunt.  There  is  also  a  cut-out  and  a  cut-out  resistance, 
the  latter  being  made  equal  to  the  normal  resistance  of  the  arc. 
The  cut-out  and  its  resistance  are  required  so  that  if  the  lamp  is 
turned  out  intentionally,  or  cuts  itself  out  through  the  failure  of 
the  carbons  to  feed,  the  other  lamps  connected  in  series  with  it 
will  not  be  affected.  If  the  resistance  were  not  used,  the  cur- 
rent would  increase  decidedly  when  one  lamp  is  cut  out,  even  if 
there  are  five  in  series.  Cutting  out  the  second  light  would  make 
a  still  further  increase  in  the  current,  and  this  increase  would 
probably  be  sufficient  to  burn  out  the  magnet  coils  of  the  three 
lamps  left  in  the  circuit.  The  steadying  resistance  shown  to  the 
left  of  the  cut-out  resistance  is  for  the  purpose  of  balancing 
the  voltage  not  required  for  the  lamp  proper.  If  five  lamps  are 
connected  in  series  on  a  500  volt  circuit,  the  voltage  correspond- 
ing to  each  lamp  will  be  100,  and  as  the  voltage  of  the  arc  is 
about  75,  there  must  be  an  additional  resistance  able  to  balance 
about  25  volts.  Some  of  this  resistance  is  placed  in  the  voltage 
adjusting  resistance,  but  the  bulk  of  it  is  in  the  top  resistance. 
When  the  lamp  is  switched  into  circuit  by  turning  the  switch  to 
the  "  On  "  position,  as  in  the  diagram,  the  current  from  binding 


HANDBOOK    ON    ENGINEERING. 


143 


post  P  passes  to  the  switch,  thence  to  the  upper  carbon,  through 
the  arc  to  the  lower  carbon,  and  then  through  the  series  magnet 
coil  and  the  steadying  resistance  to  the  N  binding  post.  The 
current  for  the  shunt  magnet  coil  starts  from  the  left  side 


switch  contact,  and  passing  through  the  shunt  coil  connects 
with  the  wire  running  from  the  upper  end  of  the  series  coil 
to  the  righ.  side  of  the  resistance.  The  circle  that  repre- 


144  HANDBOOK   ON   ENGINEERING. 

sents  the  cut-out  contact  is  connected  with  the  right  side  of  the 
cut-out  resistance,  so  that  when  the  cut-out  acts,  post  P  is  con- 
nected directly  with  post  JV  through  the  cut-out  and  steadying 
resistances. 

The  mechanism  of  the  Westingnouse  multiple  series  lamp  is 
shown  at  A,  in  Fig.  121,  a  diagrammatic  representation  of  the 
same  is  given  at  B,  and  the  lamp  complete  is  shown  at  C.  As 
will  be  seen  there  are  two  magnets,  a  series  and  a  shunt,  just  as  in 
the  Fort  Wayne  lamp.  The  voltage  and  current  adjusting  re- 
sistances are  not  used,  but  in  their  stead  a  weight  is  placed  upon 
the  clutch  actuating  lever,  and  the  necessary  adjustment  is  ob- 
tained by  setting  this  weight  in  the  proper  position.  In  each 
lamp  there  is  placed  a  cut-out  resistance,  that  is  equal  to  the  re- 
sistance of  the  arc  when  burning  normally.  This  resistance  is 
shown  at  the  lower  portion  of  the  diagram.  The  way  in  which 
the  cut-out  acts  is  so  clearly  shown  as  to  require  no  explanation. 
The  resistance  to  balance  the  excess  of  voltage  is  located  in  the 
drum  above  the  lamp,  but  in  many  cases  the  drum  is  not  used, 
and  the  resistance  is  placed  in  a  separate  casing  adapted  to  be 
fastened  to  the  wall. 

The  General  Electric  Company  make  a  lamp  for  multiple  series 
operation  that  is  practically  the  same  as  their  110  volt  constant 
potential  lamp.  The  only  difference  between  it  and  the  latter  is 
that  it  is  provided  with  an  adjusting  weight  by  means  of  which 
the  several  lamps  in  a  series  are  made  to  move  the  clutch  lever 
alike  for  the  same  strength  of  current.  This  adjusting  weight  is 
carried  on  a  bell  crank  pivoted  on  the  under  side  of  the  cap  of  the 
lamp,  as  is  clearly  shown  at  J3,  in  Fig.  122.  The  other  end  of 
the  bell  crank  is  connected  with  the  magnet  armature  through  a 
link.  By  properly  setting  the  weight  on  the  lever  in  the  several 
lamps,  all  will  work  the  same,  the  magnet  of  each  one  holding  its 
armature  in  the  same  position  for  the  same  current  strength.  By 


HANDBOOK    ON    ENGINEERING. 


145 


means  of  this  simple  mechanical  device   the  shunt  magnet  is  dis* 
pensed  with,  and  the  mechanism  is  correspondingly  simplified. 

In  most  cases  this  lamp  is  not  provided  with  a  cut-out,  so  that 
if  a  lamp  fails  to  operate  it  will  go  out  and  so  will  the  other  lamps 
in  the  series  with  it.  The  operation  of  the  lamp  is  considered  to 
be  so  reliable  that  unless  it  is  an  unusual  case  no  cut-out  is  provided. 
When  a  cut-out  is  installed  it  is  placed  in  a  separate  casing  and 


A  B  C 

Fig.  122.    General  Electric  Multiple  Series  Arc  Lamp 
for  Power  Circuits  Direct  Current. 

is  suspended  above  the  lamp  as  shown  in  A,  Fig.  122.  This  cut- 
out is  so  arranged  that  if  a  lamp  goes  out  it  can  be  removed  to  be 
readjusted  without  interfering  with  the  operation  of  the  other 
lamps  in  the  series.  The  wiring  diagram  for  this  cut-out  is  shown 
at  0,  and  as  will  be  seen  it  consists  of  the  cut-out  resistance  and 
a  magnet  directly  under  it.  The  coil  of  this  magnet  is  connected 
in  series  with  the  lamp  so  that  it  will  hold  the  switch  under  it 

10 


146  HAr^rfOOK    ON    ENGINEERING. 

open  as  long  as  current  flows  through  the  lamp,  but  it  current 
fails  to  pass  through  the  lamp  the  switch  will  close  and  the  cur- 
rent will  pass  through  the  cut-out  resistance,  and,  as  can  be  seen, 
the  lamp  can  then  be  disconnected  without  opening  the  circuit. 

ENCLOSED  ARC    LAMPS    FOR    CONSTANT    POTENTIAL 
ALTERNATING  CURRENT  CIRCUITS. 

The  only  difference  between  constant  potential  arc  lamps  for 
alternating  and  for  direct  currents  is  that  in  the  latter  a  balan- 
cing or  steading  resistance  is  used  to  balance  the  voltage  not  util- 
ized in  the  lamp,  while  in  the  former  a  choke  coil  is  employed  to 
perform  the  same  office.  A  choke  coil  cannot  be  used  in  the  di- 
rect current  lamps,  because  it  will  not  have  any  choking  effect 
when  traversed  by  a  direct  current.  For  information  on  this 
point  see  the  section  on  alternating  currents. 

A  resistance  coil  placed  in  the  circuit  absorbs  energy  in  pro- 
portion to  the  voltage  it  balances,  so  that  in  a  direct  current  lamp 
on  a  110  volt  circuit,  if  the  resistance  balances  35  volts,  and  the 
arc  75,  then  the  energ}7  made  useful  in  the  lamp  will  be  to  the  en- 
ergy lost  in  the  resistance  as  75  is  to  35.  A  choke  coil  does  not 
absorb  energy  in  proportion  to  the  voltage  it  balances,  or  any- 
thing like  this  amount.  A  choke  coil  sets  up  a  back  pressure, 
but  the  actual  amount  of  energy  it  absorbs  is  only  that  neces- 
sary to  pass  the  current  through  the  wire,  and  this  is  generally 
only  a  small  percentage  of  the  portion  of  the  voltage  balanced. 
Owing  to  this  fact  alternating  current  lamps  on  constant  potential 
circuits  are  far  more  efficient  in  so  far  as  the  use  of  the  electrical 
energy  is  concerned,  than  direct  current  lamps  ;  for  while  the  lat- 
ter lose  25  to  30  per  cent  of  the  energy,  the  former  only  lose  two 
or  three  per  cent.  Direct  current  lamps,  however,  give  more 
light  for  the  same  amount  of  electrical  energy,  so  that  the  practi- 
cal  result  is  about  the  same  for  both  types. 


HANDBOOK    ON    ENGINEERING. 


147 


The  mechanism  of  a  Fort  Wayne  alternating  current  constant 
potential  lamp  is  shown  at  A  in  Fig.  123,  and  a  diagrammatic  rep- 
resentation of  the  same  is  given  at  B.  Comparing  this  latter  il- 
lustration with  the  diagram  of  Fig.  119,  it  will  be  seen  that  they 
look  very  much  alike,  in  fact  the  only  difference  is  that  the 
steadying  resistance  of  the  latter  is  replaced  by  a  reactance, 
choke  coil.  In  other  respects  the  two  lamps  are  the  same.  In 


A 


B 


Fig.  123.    Fort  Wayne  Arc  Lamp  for  Constant  Potential 

Alternating  Current  Circuits. 

the  direct  current  lamp,  means  .are  provided  for  cutting  in  more 
or  less  of  a  voltage  regulating  resistance,  which  as  already  stated 
is  really  a  part  of  the  steadying  resistance ;  in  the  alternating 
current  lamp,  the  reactance  coil  is  made  with  a  number  of  con- 


148 


HANDBOOK    ON    ENGINEERING. 


nections  to  different  parts  of  its  convolutions,  so  that  more  or  less 
of  it  may  be  cut  into  the  circuit. 

In  the  construction  of  the  magnet  cores  of  the  alternating  and 
the  direct  current  lamps  there  is  a  decided  difference.  The  direct 
current  lamps  are  made  with  solid  iron  cores,  but  the  magnets  of 
the  alternating  current  lamps  have  laminated  cores,  made  of  very 
thin  sheet  iron  or  soft  steel.  This  difference  is  necessary  owing 


A  B 

Fig.  124.    Westinghonse  Lamp  for  Constant  Potential 
Alternating  Current  Circuits. 

to  the  fact  that  in  a  solid  core  the  alternating  current  would  in- 
duce an  electric  current  that  would  soon  make  the  metal  very  hot 
and  the  strength  of  the  magnet  w»ould  be  practically  nothing. 

The  mechanism  of  the  Westinghouse  constant  potential  lamp 
for  alternating  currents  is  shown  at  A  in  Fig.  124.  A  diagram 
of  the  same  is  ahown  at  B.  Comparing  Figs.  118  and  124  it 


HANDBOOK    ON   ENGINEERING. 


149 


will  be  seen  that  the  resistance  coil  of  the  former  is  replaced  by  a 
reactance  coil.  The  direct  current  lamp,  Fig.  118,  has  two  mag- 
net coils  to  pull  down  the  clutch  actuating  lever,  while  the  alter- 
nating current  lamp,  Fig.  124,  has  only  one  coil,  but  both  lamps 
operate  in  the  same  way.  By  comparing  the  diagrams  of  the  two 
lamps  their  similarity  is  seen  at  once. 

The  mechanism,  the  external  appearance,  and  the  diagram  of 


Fig.  125.    General  Electric  Lamp  for  Constant  Potential 
Alternating  Current  Circuits. 

connections  of  the  General  Electric  constant  potential  lamp  are 
given  in  Fig.  125.  The  principle  of  operation  of  this  lamp  is  the 
same  as  that  of  the  other  two  explained  in  the  foregoing.  The 
diagram  shows  very  clearly  how  the  magnet  pulls  directly  upon 
the  clutch  connecting  link. 


150 


HANDBOOK    ON    ENGINEERING. 


THE  FORT  WAYNE  HULTIPLE  ALTERNATING  CURRENT 
STREET  ARC    LIGHTING  SYSTEM. 

The  Fort  Wayne  Company  make  an  alternating  current  street 
lighting  system  of  the  constant  potential  type  that  is  intended  for 
small  towns  or  for  places  where  there  are  several  centres  in  which 


Fort  Wayne  System. 

General  Plan  of  Multiple  Alternating  Current 
Street  Arc  Lighting  System. 
Fig.  126. 

numerous  lights  are  used,  these  centres  being  some  distance  from 
each  other  and  from  the  central  station.  The  general  principle 
of  the  system  is  to  generate  an  alternating  current  of  high  voltage 


HANDBOOK    ON   ENGINEERING. 


151 


at  a  central  station,  and  to  convey  this  to  the  centres  of  distribu- 
tion where  it  is  utilized  in  arc  lamps  through  individual  trans- 
formers which  develop  secondary  currents  of  the  voltage  and 
amperage  required  for  the  lamps.  The  system  is  designed  so  as 
to  be  used  for  incandescent  lighting  as  well  as  arc. 


Fig.  127.    Fort  Wayne  Enclosed  Are  Lamp  Used  with 
System  Illustrated  in  Diagram  Fig.  126. 

The  diagram  Fig.  126,  shows  the  general  arrangement  of  the 
system.  The  alternator  and  switchboard  shown  are  supposed  to 
be  located  at  the  central  station,  probably  several  miles  distant. 
The  wires  coming  from  the  alternator  are  connected  with  lower 
terminals  of  the  two  pole  switch  and  also  the  arc  circuit  switch. 
From  the  upper  terminals  of  the  two  pole  switch  the  connections 


152  HANDBOOK    ON    ENGINEERING. 

run  out  to  the  transmission  lines,  the  ammeter  being  connected  in 
one  of  these  connections.  At  the  centres  of  distribution  these 
line  wires  are  connected  with  the  primary  coils  of  step-down 
transformers  that  furnish  current  for  incandescent  lighting. 
From  the  upper  terminal  of  the  arc  circuit  switch  a  connection 
runs  out  to  a  third  transmission  line  which  also  goes  to  the  cen- 
tres of  distribution.  At  these  centres,  the  primary  coils  of  small 
transformers,  each  one  of  sufficient  capacity  to  operate  one  arc 
lamp,  are  connected  with  the  arc  transmission  main,  and  one  of 
the  incandescent  mains,  as  clearly  shown  in  the  diagram.  These 
small  transformers  are  proportioned  so  that  they  give  a  secondary 
current  of  about  6  amperes  and  77  volts,  or  just  sufficient  to  op- 
erate a  lamp.  The  transformers  which  are  shown  directly  above 
the  lamp  in  the  diagram,  are  placed  in  any  convenient  position, 
generally  at  the  top  of  the  arc  light  pole. 

As  the  transformer  furnishes  a  current  of  the  proper  voltage 
for  the  lamp  no  reactance  coil  is  required  in  the  latter,  and  as  a 
consequence  the  construction  is  considerably  simplified,  as  can  be 
seen  from  Fig.  127  which  shows  the  lamp  mechanism  at  A  and 
the  diagram  of  connections  at  B. 

LUMINOUS  OR  FLAMING  ARC  LAHPS. 

Open  arc  lamps  frequently  give  a  poor  light  owing  to  the  fact 
that  the  carbons  are  of  inferior  quality,  and  as  a  result  are  va- 
porized by  the  heat  of  the  arc.  This  vapor  burns  and  produces 
a  reddish  or  purple  flame  that  not  only  changes  the  color  of  the 
light,  but  reduces  its  brilliancy.  By  experimenting  with  carbons 
of  different  composition  it  has  been  found  that  the  flame  pro- 
duced can  be  varied  in  color,  and  at  the  same  time  can  be  intens- 
ified so  that  it  will  give  a  strong  light.  Thus  that  which  was 
originally  an  objectionable  feature  of  arc  lamps  has  been  made 
use  of  in  developing  a  new  type  of  lamp  in  which  the  flaming  ac- 


HANDBOOK    ON   ENGINEERING. 


153 


tion  is  increased,  and  the  brilliancy  of  the  flame  is  depended 
upon  to  give  the  color  of  light  desired,  and  also  the  intensity. 
Lamps  that  operate  on  this  principle  are  called  Flaming  arc 
lamps  and  also  Luminous  arc  lamps.  At  the  present  time  they 
are  used  quite  extensively  in  Europe,  and  are  rapidly  gaining 
headway  in  this  country,  owing  to  the  fact  that  they  give  more 


ABC 
Fig.  128.    Excello  Luminous  Arc  Lamp. 

A. —Diagram  of  Mechanism  and  Circuit  Connections  for  Direct  Current  Lamp. 
C.— Diagram   of  Mechanism   and  Circuit  Connections  for  Alternating  Current 
Lamp. 

light  for  the   same  amount  of  current  energy  and  the  light  is  of  a 
very  fine  color,  being  nearly  white. 

THE  EXCELLO  LUMINOUS  ARC  LAMP. 

In  Fig*  128,  the  Excello  Luminous  Arc   Lamp   is   shown,   the 


154  HANDBOOK    ON    ENGINEERING. 

diagram  A  being  that  of  the  direct  current  lamp,  and  C  that  of 
the  alternating  current  lamp.  As  will  be  seen,  in  both  diagrams, 
the  carbon  rods  are  set  at  an  incline  toward  each  other,  and  are 
held  up  by  chains  that  pass  around  a  drum.  The  weight  of  the 
carbon  rods  furnishes  the  force  required  to  rotate  the  drum,  and 
clock  work  controls  the  velocity  of  rotation  when  the  catch /is 
drawn  out  of  the  way. 

In  the  direct  current  lamp,  diagram  A,  there  is  a  series  mag- 
net at  the  side  of  the  drum,  which  depresses  rod  b  when  the  cur- 
rent is  turned  on,  and  through  the  links  at  the  bottom  separates 
the  carbons.  The  shunt  magnet  n  then  becomes  strong  enough 
to  draw  e  around  and  lift  b  and  cause  the  slider  d  to  bring  the 
carbons  together  to  strike  the  arc.  As  the  carbons  burn  away  e 
rotates  further  owing  to  the  fact  that  the  shunt  magnet  n  becomes 
stronger.  When  e  moves  far  enough /is  pulled  out  of  the  way  and 
then  the  clock  work  begins  to  rotate  and  the  chains  on  the  drum 
unwind  thus  permitting  the  carbons  to  feed  down.  When  the 
carbons  are  fully  consumed,  a  small  detent  on  the  chain  stops  the 
further  feeding  and  then  when  the  arc  becomes  sufficiently  long 
the  current  breaks  and  the  lamp  goes  out. 

The  diagram  C  shows  the  alternating  current  lamp.  In  this 
lamp  there  is  a  small  disc  that  is  rotated  in  one  direction  by  the 
action  of  the  series  magnet  H  and  in  the  opposite  direction  by 
the  shunt  magnet  N.  When  the  current  is  turned  on  the  series 
magnet  H  rotates  the  disc  in  a  direction  that  lifts  and  separates 
the  carbons.  As  the  carbons  separate,  the  force  of  the  shunt 
magnet  increases  and  gradually  counteracts  the  force  of  H  so 
that  when  the  arc  is  of  the  proper  length,  the  disc  stops  turning. 
As  the  carbons  burn  away  the  shunt  magnet  becomes  stronger  and 
then  by  overpowering  H  causes  the  disc  to  rotate  in  the  opposite 
direction  thus  causing  the  carbons  to  feed  down. 

These  lamps  are  made  so   as  to   run   with  currents  of  6.8,   10 


HANDBOOK    ON   ENGINEERING. 


155 


and  12  amperes,  and  are  burned  two  in  series  on  115  volt  circuits, 
or  four  in  series  on  230  volts.  For  the  same  amount  of  electri- 
cal energy  they  give  more  light  than  regular  enclosed  arc  lamps. 
The  carbons  last  about  18  hours.  The  light  is  clear  white,  but 
for  advertising  purposes  it  can  be  made  of  different  colors  by 
changing  the  composition  of  the  carbons.  Just  above  the  arc  is 


A  B 

Fig.  129.    General  Electric  Luminous  Arc  Lamp. 

placed  a  small  porcelain  reflector  i  which  acts  as  a  protector  of  the 
parts  above  the  flame  and  also  as  a  reflector. 

Fig*  J29  shows  a  flaming  arc  lamp  made  by  the  General  Electric 
Company.  At  A  is  seen  the  external  appearance  of  the  lamp 
while  B  shows  the  mechanism.  In  this  lamp  the  lower  carbon  is 


156  HANDBOOK    ON    ENGINEERING. 

a  composition  contained  in  an  iron  tube  and  is  fed  upward  by  the 
magnets  above  the  arc  through  the  side  connection  as. shown  in 
B.  The  main  frame  of  the  lamp  consists  of  a  central  tube  of 
good  size  that  serves  as  a  chimney  to  carry  off  the  fumes  from 
the  arc.  The  lower  carbon  burns  for  about  150  hours.  In  place 
of  an  upper  carbon,  a  copper  disc  is  used  and  this  is  of  such  size 
that  it  remains  comparatively  cool  so  that  its  life  is  about  2000 
hours.  The  arc  remains  in  the  same  position  all  the  time  so  that 
a  reflector  made  of  enameled  iron  can  be  secured  stationary  just 
above  the  arc. 

This  lamp  is  made  for  direct  currents  to  operate  in  series  and 
consumes  a  current  of  four  amperes  at  an  e.  m.  f .  of  about  75 
volts.  Its  light  giving  efficiency  is  said  to  be  very  high. 

GENERAL  DIRECTIONS  FOR  THE  CARE  AND  OPERATION  OF 
ENCLOSED  ARC  LAMPS  OF  ALL  TYPES. 

It  is  not  practicable  to  give  in  this  book  detailed  directions  for 
the  operation  and  care  of  each  and  every  make  of  enclosed  arc 
lamp  on  the  market,  as  there  are  so  many  of  them  that  such  di- 
rections would  fill  a  volume  by  themselves.  In  what  follows  di- 
rections are  given  that  apply  to  all  types  of  lamps,  but  any  one 
desiring  minute  directions  relative  to  any  particular  lamp  can 
easily  obtain  them  by  applying  to  the  manufacturers  who  publish 
instruction  books  that  contain  all  this  information. 

Carbons:  For  alternating,  as  well  as  direct  current  lamps, 
only  the  highest  grade  of  carbons  should  be  used,  as  they  not 
only  give  a  better  and  more  steady  light,  but  they  last  much 
longer. 

For  direct  current  lamps  only  solid  carbons  should  be  used. 

For  alternating  current  lamps  one  of  the  carbons  should  be 
solid  and  the  other  cored. 

No  carbons  should  be  used  that  are  not  perfectly  straight, 
round  and  smooth,  if  they  are  not  smooth  rub  them  with  a  piece 
of  sand  paper  to  take  off  the  blisters  and  lumps. 


HANDBOOK    ON    ENGINEERING.  157 

It  is  necessary  that  the  carbons  be  very  nearly  the  proper  di- 
ameter to  enable  the  lamp  to  feed  properly.  The  manufacturers 
furnish  a  gauge  provided  with  two  holes,  and  all  carbons  that 
pass  through  the  smaller  hole  as  well  as  those  that  will  not  pass 
through  the  larger  hole  are  to  be  rejected  as  too  large  and  too 
small  to  be  used.  The  maximum  variation  from  the  standard  di- 
ameter is  not  quite  one  hundredth  of  an  inch  either  under  or  over 
size. 

In  direct  current  lamps,  if  the  upper  carbon  is  12"  long,  the 
lower  one  should  be  5J"  and  in  almost  every  case  the  stump 
left  in  the  upper  holder  when  the  carbons  have  burned  out  is  used 
for  the  lower  carbon  in  the  next  trimming,  as  it  is  of  ample  length 
for  the  purpose. 

For  alternating  current  lamps  the  upper  carbon  12"  and  the 
lower  one  7".  Most  of  the  carbons  used  are  ^"  diameter,  but 
T7^"  and  |"  are  also  used  in  direct  current  lamps.  Some  lamps 
are  also  made  so  as  to  use  9"  carbons  in  the  upper  holder. 

If  the  lamps  are  in  good  order,  with  tight  fitting  globes,  and 
the  carbons  are  first  class,  they  should  burn  for  about  150  hours 
before  requiring  retrimming,  that  is  for  12"  upper  carbon,  J"  di- 
ameter. This  is  the  life  for  direct  current ;  for  alternating  cur- 
rent lamps  the  life  is  about  100  hours. 

How  to  trim  lamps :  In  trimming  or  renewing  the  carbons  in 
a  lamp  care  should  be  taken  that  the  upper  carbon  is  pushed  up 
as  far  as  it  will  go,  so  as  to  make  a  good  contact  with  the  holder. 
So  as  to  facilitate  this  operation  it  is  best  to  use  carbons  with  a 
tapering  end. 

Be  sure  that  the  carbon  slides  freely  through  the  clutch  and  the 
metal  cap  of  the  enclosing  globe. 

Remove  the  dust  from  around  the  gas  check  and  see  that  the 
mechanism  all  works  freely,  if  this  is  not  done,  the  lamp  will  not 
burn  well,  and  will  probably  lengthen  the  arc  and  thus  shorten 
the  life  of  the  carbons. 


158  HANDBOOK    ON    ENGINEERING. 

Never  put  oil  in  the  dash  pot,  it  is  made  to  work  dry. 

To  secure  a  good  light  the  inner  enclosing  globe  should  be 
cleaned  every  time  new  carbons  are  put  in,  so  as  to  remove  the 
coating  deposited  by  the  gas  from  the  arc.  In  large  stations  it 
is  the  custom,  generally,  to  provide  duplicate  lower  carbon 
holders,  and  these  are  trimmed  and  secured  to  the  globe  and  are 
then  placed  in  baskets  provided  with  partitions  to  receive  them. 
They  are  carried  by  the  trimmers  in  a  wagon  and  then  in  trim- 
ming the  lamps  the  old  globe  with  the  lower  carbon  holder  is  re- 
placed by  the  new  one.  This  saves  the  trouble  of  cleaning  the 
globe  and  inserting  the  lower  carbon  at  the  lamp. 

In  order  that  the  life  of  the  carbons  may  be  long  it  is  necessary 
that  the  enclosing  globe  be  fitted  perfectly  tight,  if  air  can  get  in 
the  carbons  will  soon  burn  out.  Owing  to  this  fact  the  edge  of 
the  globes  should  be  well  examined  every  time  the  lamp  is 
trimmed  to  make  sure  that  there  are  no  pieces  nicked  out,  and 
care  should  be  taken  to  see  that  the  globes  come  down  properly 
to  their  seats,  and  make  a  tight  joint.  Never  try  to  burn  an  en- 
closed arc  lamp  with  the  enclosing  globe  removed.  Keep  all  the 
electrical  contacts  tight. 

Be  sure  that  the  dash  pots  always  work  freely. 

Make  sure  that  the  upper  carbon  does  not  bind. 

Lamps  should  be  suspended  from  a  strong  support. 

The  clutch  should  work  smoothly  and  reliably. 

Use  no  crooked,  rough,  dirty  or  inferior  carbons. 

Always  have  top  carbon  positive.  If  you  do  not  know  whether 
it  is  positive  or  not,  light  the  lamp  for  a  few  minutes,  then  put  it 
out  and  the  top  carbon  will  remain  hot  longer  than  the  lower  one, 
if  it  is  positive. 

Do  not  use  any  inner  globes  that  are  cracked,  nicked  or  do  not 
fit  tightly  against  their  seats. 

Use  no  oil  on  any  part  of  the  lamp  where  it  can  possibly  get  on 
the  carbons,  as  this  will  cause  flickering  and  flaming. 


HANDBOOK   ON   ENGINEERING.  159 

Keep  under  side  of  gas  cap  clean  and  bright  by  wiping  at  each 
trimming.  The  bright  metal  attracts  the  gases  and  prevents 
them  from  depositing  on  the  globe. 

Remove  the  casing  that  encloses  the  mechanism  occasionally 
and  inspect  the  parts  carefully  for  possible  faults. 

Keep  the  space  between  carbon  bushings  in  the  gas  cap  clean 
and  free  from  dust. 

Renew  the  bushings  whenever  they  show  much  wear,  as  increase 
in  the  diameter  of  the  hole  permits  more  air  to  enter  the  globe 
around  the  carbon  and  this  shortens  the  life  of  the  carbons. 

Be  sure  to  wipe  inner  globes  clean  at  each  trimming  so  as  to 
prevent  deposits  from  forming.  Should  deposits  form  that  can- 
not be  wiped  off,  they  can  be  removed  with  a  weak  solution  of 
muriatic  acid. 

Never  run  alternating  current  lamps  on  the  wrong  frequency. 
Many  alternating  lamps  are  made  to  run  on  different  frequencies 
by  slightly  changing  the  connections.  For  information  as  to  how 
to  make  these  changes  see  instruction  books  of  the  makers  of  the 
lamp. 

Installing  lamps :  Lamps  should  not  only  be  installed  in  places 
where  they  will  destribute  light  over  the  greatest  possible  area, 
but  also  where  they  are  easily  accessible  when  it  is  desired  to 
trim  or  inspect  them. 

Outdoor  lamps  should  be  suspended  from  25  to .  30  feet  from 
the  ground,  to  give  the  best  service,  and  in  positions  where  their 
light  will  be  obstructed  as  little  as  possible.  The  distance  be- 
tween lamps  should  not  be  more  that  about  300  feet  to  obtain 
satisfactory  illumination.  The  globes  used  for  outdoor  lighting 
should  be  clear,  for  the  inner  as  well  as  the  outer  globe. 

For  indoor  lighting  the  inner  globe  should  be  ground  glass  or 
opal,  the  outer  one  clear  glass.  For  outdoor  lighting  metal  re- 
flectors are  commonly  used,  but  no  reflector  is  used  with  indoor 
lamps. 


HANDBOOK  ON  ENGINEERING, 


CHAPTER    Xa. 

Incandescent  Wiring  Table. 

Table  on  two  following  pages  is  arranged  to  enable  wiremen  to 
select  the  right  sizes  of  wire  for  service  connections  and  inside 
work.  The  figures  at  the  top  indicate  distance  in  feet  to  center 
of  distribution,  in  reality  half  the  length  of  the  circuit ;  the  four 
columns  at  the  left  showing  the  number  of  16-candle  power  lamps 
at  various  voltages;  the  other,  figures  showing  the  sizes  of  wire, 
Brown  &  Sharpe  gauge,  to  be  used  for  distributing  the  number  of 
lamps  stated  at  the  distances  indicated  and  with  the  loss  of  1 
volt. 

For  example:  To  distribute  30  lamps  of  110  volts  at  a  dis- 
tance of  80  feet  with  a  loss  of  1  volt.  In  colamn  of  110-volt 
lamps  find  the  number  30,  then  follow  the  same  line  of  figures  to 
the  right  until  the  column  headed  80  is  reached,  and  it  appears 
that  No.  6  wire  must  be  used. 

The  same  table  may  be  used  for  other  losses  than  1  volt  by 
dividing  the  given  number  of  lamps  by  the  number  of  volts  to  be 
lost,  then  with  this  product  proceed  as  before  in  the  table. 

For  example :  To  distribute  30  lamps  of  110  volts  at  a  distance 
of  80  feet  with  a  loss  of  2  volts,  divide  30  by  2  which  gives  15, 
then  find  15  in  the  column  headed  110  volts  and  follow  the  same 
line  of  figures  to  the  right  until  column  headed  80  is  reached,  and 
it  is  found  that  No.  8  wire  must  be  used. 

No  wire  smaller  than  No.  14  is  shown  in  the  table  as  the  Na- 
tional Board  of  Fire  Underwriters  prohibits  the  use  of  a  smaller 
size.  Odd  sizes  smaller  than  No.  5  are  not  commercial  and  are 
therefore  omitted. 


HANDBOOK  ON  ENGINEERING. 

Incandescent  Wiring:  Table. 

Sixteen  Candle  Power  Lamps.  Lo«s  One  Volt 

TABLE  No.  1.          Sizes  of  Wire  are  by  B.  &  S.  Gauge. 


161 


52  Volt 
3i 

110  Volt 
34 

220  Volt 
4 

550  Volt 
4 

Distance  in  feet  to  center 
of  Distribution. 

Watt 

Watt 

Watt 

Watt 

Lamps 

Lamps 

Lamps 

Lamps 

1 

20' 

25' 

30' 

35* 

40' 

45' 

1 

2 

3 

9 

14 

14 

14 

14 

14 

14 

2 

4 

7 

18 

14 

14 

14 

14 

14 

14 

3 

6 

11 

28 

14 

14 

14 

14 

14 

14 

4 

8 

15 

37 

14 

14 

14 

14 

14 

14 

5 

Iff 

18 

46 

14 

14 

14 

14 

12 

12 

6 

12 

23 

56 

14 

14 

14 

12 

12 

12 

7 

15 

26 

65 

14 

14 

12 

12 

12 

10 

8 

17 

30 

74 

14 

12 

12 

12 

10 

10 

9 

19 

33 

83 

14 

12 

12 

10 

10 

10 

10 

21 

37 

93 

12 

12 

12 

10 

10 

10 

12 

25 

44 

111 

12 

10 

10 

10 

8 

8 

14 

30 

52 

130 

12 

10 

10 

8 

8 

8 

16 

34 

59 

148 

10 

10 

8 

8 

8 

8 

18 

38 

66 

107 

10 

8 

8 

8 

8 

6 

20 

42 

74 

185 

10 

8 

8 

8 

6 

6 

25 

63 

92 

232 

8 

8 

6 

6 

6 

6 

80 

63 

111 

278 

8 

6 

6 

6 

5 

5 

$5 

74 

130 

324 

6 

6 

6 

5 

5  I 

4 

40 

85 

148 

371 

6 

6 

6 

5 

4 

4 

45 

95 

166 

428 

5 

5 

5 

4 

4 

3 

60 

106 

185 

464 

5 

5 

4 

4 

3 

3 

55 

116 

203 

510 

4 

4 

4 

3 

3 

2 

€0 

127 

222 

557 

4 

4 

4 

3 

2 

2 

65 

138 

240 

603 

3 

3 

3 

3 

2 

2 

70 

148 

260 

650 

3 

3 

3 

2 

2 

1 

75 

159 

277 

696 

2 

2 

2 

2 

1 

1 

80 

170 

296 

742 

2 

2 

2 

2 

1 

1 

90 

191 

333 

835 

1 

1 

1 

1 

1 

0 

100              212 
il 

370 

92$ 

1 

1 

1 

1 

0 

0 

Iff2  HANDBOOK   ON   ENGINEERING 

Incandescent  Wiring,  Table. 

Sixteen  Candle  Power  Lamps,  Loss,  One  Volt. 
TABLE  No.  la.         Sizes  of  Wire  are  by  B.  &  S.  Gauge. 

DISTANCE    IN    FKET    TO    CENTER   OP    DISTRIBUTION. 


60' 

60' 

70' 

80' 

HO' 

100' 

120' 

140' 

IbO' 

180' 

200' 

14 

14 

14 

14 

14 

14 

14 

14 

14 

14 

12 

14 

14 

14 

14 

14 

12 

12 

12 

10 

10 

10 

14 

14 

12 

12 

12 

10 

10 

10 

8 

8 

8 

12 

12 

12 

10 

10 

10 

8 

8 

8 

8 

6 

12 

10 

10 

10 

10 

8 

8 

8 

6 

6 

6 

10 

10 

10 

8 

8 

8 

8 

6 

6 

6 

6 

10 

10 

8 

8 

8 

8 

G 

G 

G 

5 

5> 

10 

8 

8 

8 

8 

G 

G 

6 

5 

5 

4 

10 

8 

8 

8 

6 

G 

6 

5 

5 

4 

4 

8 

8 

8 

G 

G 

G 

5 

5 

4 

4 

a 

8 

8 

6 

G 

6 

5 

5 

4 

3 

3 

2 

8 

C 

6 

G 

5 

5 

4 

3 

3 

2 

2 

6 

C 

6 

5 

5 

4 

3 

3 

2 

2 

1 

0 

G 

5 

5 

4 

4 

a 

2 

2 

1 

1 

6 

5 

5 

4 

4 

3 

2 

2 

1 

1 

0 

5 

5 

4 

3 

3 

2 

1 

1 

0 

0 

OOi 

5 

4 

3 

2 

2 

1 

1 

0 

0 

00 

00 

4 

3 

o 

2 

1 

1 

0 

00 

00 

000 

000 

3 

2 

2 

1 

1 

0 

00 

00 

000 

000 

0000 

3 

2 

1 

1 

0 

0 

00 

000 

000 

0000 

0000 

2 

1 

1 

0 

0 

00 

000 

000 

0000 

0000 

1 

* 

1 

0 

0 

00 

00 

000 

0000 

0000 

\ 

1 

0 

00 

00 

000 

000 

0000 

0000 

I 

0 

0 

00 

00 

000 

0000 

0000 

1 

0 

00 

00 

000 

000 

0000 

0 

0 

00 

OOQ 

000 

0000 

(0000 

!  . 

0 

00 

00 

000 

000 

0000 

0 

00 

000 

000 

0000 

0000 

00 

000 

000 

0000 

0000 

163 


Feet  x  2  x  10,70. 


TABLE  No.  2. 


Feet 
to  end  of 
Circuit. 

Ft.  x2x!0.70. 

Feet 
to  end  of 
Circuit. 

Ft.x2xlO.70. 

Feet 
to  end  of 
Circuit. 

Ft.  x2x  10.70. 

5 

107 

185 

3,969 

365 

7,8.11 

10 

214 

190 

4,066 

370 

7,918 

15 

321 

195 

4,173 

375 

8,025 

20 

428 

200 

4,280 

380 

8,132 

25 

535 

205 

4,387 

385 

8,239 

30 

642 

210 

4,494 

390 

8,346 

35 

749 

215 

4,601     : 

395 

8,453 

40 

856 

220 

4,708 

400 

8,560 

45 

963 

225 

4,815 

405 

8,667 

50 

,070 

230 

4,922 

410 

8,774 

55 

,177 

235* 

5,029 

415 

8,381 

60 

,284 

240 

5,136 

420 

8,988 

65 

,391 

245 

6,243 

425 

9,095 

70. 

.498 

250 

6,350 

430 

9,202 

75 

,605 

255 

5,457 

435 

9,309 

80 

J12 

260 

5,564 

440 

9,416 

85 

,819 

265 

6,671 

44$ 

9,523 

90 

,926 

270 

5,778 

450 

9,630 

95 

2,033 

215 

6,885  . 

455 

9,737 

100 

2,140 

280 

5,992 

460 

9,844 

105 

2,247 

285 

6,099 

465 

9,951' 

110 

2,354 

290 

6,206 

470 

10,058 

115  ' 

2,461 

295 

6,313 

475 

10,165 

120 

2,568 

300 

6,420 

480 

10,272 

125 

2,675 

305 

6,527 

485 

10,379 

130 

§,782 

310 

6,634 

490 

10,486 

135 

2,889 

315 

6,741   i 

495 

10,693 

140 

2,996 

320 

6,848 

600 

10,700 

145 

3,103 

325 

6,955 

510 

10,914. 

150 

3,210 

330 

7,06fc 

520 

11,128. 

155 

3,317 

335. 

7,169 

530 

11,342 

160 

3,424 

340 

7,276 

640 

11,555 

165 

3,531 

345 

7,383 

550 

11.770 

170 

'3,638 

350 

7,490 

560 

11,984 

175 

8,745 

355 

7,«97 

570 

12,198 

180 

3,852 

360 

7,704 

580 

12,412 

HANDBOOK  ON  ENGINEERING. 
Feet  x  2  x  10.70. 


TABLE  No.  2. 


Feet 
to  end  of 
Circuit. 

Ft.  x2x!0.70. 

Feet 
to  end  of 
Circuit. 

Ft.x2xlO.70 

Feet 
to  end  of 
Circuit. 

Ft.  X2X10.7Q 

690 

12,626 

970 

20,753 

1,350 

28,890 

600 

12,840 

980 

20,972 

1,360 

29,104 

610 

13,054 

900 

21,186 

1,370 

29,318 

620 

13,268 

1,000 

21,400 

1,380 

29,535? 

630 

13,482 

1,010 

21,614 

1,390 

29,746 

640 

13,^696 

1,020 

21  j  #28 

1,400 

29,960 

650 

13,910 

1,030 

22,042 

1,410 

30,174 

660 

14,124 

1,040 

22,256 

1,420 

30,388 

670 

14,338 

1,050 

22,470 

1,430 

30,602 

680 

14,552 

1,060 

1;  22,684 

1,440 

30,810 

6'JO 

14,766 

1,070 

22,898 

1,450 

31,030 

700 

14,980 

1,080 

23,112 

1,460 

31,244' 

710 

15,194 

1,090 

23,326 

1,470 

31,458' 

1720 

15,408 

1,100 

23,540 

1,480 

31,672 

730  i 

J5,622 

1,110 

i!  23,764 

1,490 

31,886 

1740 

'15,836 

1,120 

23,968 

1,500 

32,100 

750 

16,050 

1,130 

24,182 

1,510 

32,314 

760  i 

56,264 

1,140 

24,396 

1,520 

32,528 

770  ..; 

16,47® 

1,150 

24,610 

1,530 

82,742 

780 

16,692 

1,160 

24,824 

1,540 

82,956 

790 

16,906 

1,170 

25,038 

1,550 

33,170 

800 

f7,120 

1,180 

25,252 

1,560 

33,384 

810 

17,334 

1,190 

25,466 

1,570 

33,598 

820 

17,548 

1,200 

25,680 

1,580 

33,812 

830- 

17,762 

1,210 

25,894 

1,590 

84,026 

840 

17,976 

1,220 

26,108 

1,600 

34,240 

850 

18,190 

1,230 

26,322 

1,610 

34,454 

860 

18,404 

1,240 

26,536 

1,620 

34,668 

870 

18,618 

1,250 

26,750 

1,630 

34,882 

880 

18,832 

1,260 

26,964 

1,640 

35,096 

890 

19,046 

1,270 

27,178 

1,650 

35,310 

900 

19,260 

1,280 

27,392 

1,660 

35,524 

910 

19,474 

1,290 

27,606 

1,670 

35,738 

920 

19,688 

1,300 

27,820 

1,680 

35,952 

930 

19,902 

1,310 

28,034 

1,690 

36,166 

940 

20,116 

1,320 

28,248 

1,700 

36,380 

950 

20,330 

1,330 

28,462 

1,710 

86,594 

960 

20,544 

1,340 

28,676 

1,720 

36,808 

HANDBOOK  ON  ENGINEERING, 


163 


Feetx  2x10.70. 


No.  2. 


Feet 

Feet 

Feet 

to  end  of 

Ft.x2xlO.70. 

to  end  of 

Ft.x2xlO.70. 

to  end  of 

Ft.x2xlO,70. 

Circuit. 

Circuit. 

Circuit. 

1,730 

37,022 

2,450 

52,430 

4,250 

90,950 

,740 

37,236 

2,500 

53,500 

4,300 

92,020 

,750 

37,450 

2,550 

54,570 

4350 

93090 

,760 

37,664 

2,600 

55,640 

4,400 

94,160 

,770 

37,878 

2,650 

56,710 

4,450 

95,230 

,780 

38,092 

2,700 

67,780 

4,500 

96300 

J90 

38,306 

2,750 

58,850 

4,550 

97,370 

,800 

38,520 

2,800 

59,920 

4,600 

98,440 

,810 

38,734 

2,850 

60,990 

4,650 

99,510 

,820 

38,948 

2,900 

62,060 

4,700 

100,580 

,830 

39,162 

2,950 

63,130 

4,750 

101,650 

,840 

39,376 

3,000 

64,200 

4,800 

102,720 

,850 

39,590 

3,050 

65,270 

4,850 

103,790 

,860 

39,804 

3,100 

66,340 

4,900 

104,860 

,870 

40,018 

3,150 

67,410 

4,950 

105,930 

,880 

40,232 

3,200 

68,480 

6,000 

107,000 

,890 

40,446 

3,250 

69,550 

6,050 

108,070 

,900 

40,660 

3,300 

70,620 

6,100 

109,140 

,910 

40,874 

3,350 

71,690 

5,150 

110,210 

,920 

41,088 

3,400 

72,760 

5,200 

111,280 

,930 

41,302 

3,450 

73,830 

5,250 

112,350 

,940 

41,516 

3,500 

74,900 

6,300 

113,420 

,950 

41,730 

3,550 

75,970 

5,350 

114,400 

1,960 

41,944 

3,600 

77,040 

5,400 

115,560 

1,970 

42,158 

3,650 

78,110 

5,450 

116,63Q 

1,980 

42,372 

3,700 

79,180 

6,500 

117,700 

1,-990 

42,586 

3,750 

80,250 

5,550 

118,770 

2,000 

42,800 

3,800 

81,320 

5,600 

119,840 

2,050 

43,870 

3,850 

82,390 

6,650 

120,910 

2,100 

44,940 

3,900 

83,460 

5,700 

121,980 

2,150 

46,010 

3,950 

84,530 

6  750 

123,050 

2,200 

47,080 

4',000 

85,600 

5,800 

124,120 

2,250 

48,150 

4,050 

86,670 

5,8*0 

125,190 

2,300 

49,220 

4,100 

87,740 

5,900 

126,260 

2,350 

50,290 

4,150 

88,810 

6,950 

127,330 

2,400 

51,360 

4,200 

89,880 

6,000 

128,400 

166 


TAB»-B  No.  2. 


HANDBOOK  OK  ENGINEERING* 

Feet  x2x  10.70. 


Miles. 

Ft.x2xlO.70 

Miles. 

Ft.x2xlO.70 

Miles. 

Ft.x2xlO.70 

ft 

564,960 

4 

451,968 

74 

847,440 

1 

112,992 

4* 

508,464 

8 

903,936 

14 

169,488 

5  i 

664.960 

64 

960.432 

2        j 

225,984 

54 

621,456 

9 

1,016,928 

24 

282,480 

6 

677,952 

94 

1,073,424 

8 

838,976 

6J 

734.448 

10 

1,129,920 

•i 

895,472 

7 

790,944 

(A) 
(B) 
(C) 


Feet  x  2  x  10.7  x  Amperes 

^Volts  lost 
Feetx  2x  10.7  x  Amperes 

Circular  mils. 
Circular  mils  x  volts  lost 


=  Circular  mi}s. 


=  Volts  lost. 


=  Amperes. 


Feetx  2x10. 7 

In  calculating  the  sizes  of  wire  as  shown  in  the  Incandescent 
Wiring  Table  a  formula  (A)  has  been  used  in  wliich  there  is  a 
Constant  10.7,  the  number  of  circular  mils  in  a  copper  wire  which 
would  have  a  resistance  of  one  ohm  for  one  foot  of  length.  One 
ampere  through  one  ohm  resistance  loses  one  volt*  To  determine 
the  size  of  wire  necessary  for  carrying  a  given  current  a  given 
distance  in  feet,  multiply  the  number  of  feet  by  2  to  obtain  the 
actual  length  of  circuit,  multiply  this  product  by  the  constant 
10.7  and  it  will  give  the  circular  mils  necessary  for  one  ohm  re- 
sistance, multiply  this  by  the  amperes  and  it  gives  the  circular 
mils  necessary  for  the  loss  of  one  volt.  Divide  this-  last  result; 
by  the  volts  lost  and  it  gives  the  circular  mils  necessary.  Hence 
the  formula  "A." 

By  simply  transposing  the  terms  we  obtain  formula  "  B,"  which 
can  be  used  to  determine  the  volts  lost  in  a  given  length  of  wire 
Of  certain  size  carrying  a  certain,  number  of  amperes. 


HANDBOOK    ON    ENGINEERING.  167 

Again,  by  another  change  in  the  terms,  we  obtain  formula 
"  C,"  which  shows  the  number  of  amperes  which  a  wire  of  given 
size  and  length  will  carry  at  a  given  number  of  volts  lost. 

Table  No.  2  has  been  arranged  for  the  purpose  of  saving  time 
in  the  use  of  these  formulas.  It  shows  the  result  of  Feet  x  2  x 
10.7  for  various  distances  over  which  it  may  be  desired  to  trans- 
mit current. 

A  few  examples  will  assist  in  showing  the  use  of  the  formulas 
and  tables. 

Suppose  we  wish  to  distribute  300  16  c.  p.  3.5  watt  lamps    of 
110  volts  at  a  distance  of  490  feet  with  a  loss  of  10  per  cent. 
Using  formula  A, 

490  feet  x  2  x  10.7  (find  it  in  table  No.  2)  =  10486. 
300  lamps  of  110  volts  =  152.7  amperes. 
(See  table  No.  3  for  amperes  per  lamp,  and  multiply  by  300) 
10  per  cent  loss  on  110  volt   system  =  12.22  volts.       (See 

table  No.  4.) 
10486  x  152.7  amperes  =  1601212  circ.  mils,  -v-12.22  volts 

lost=  131032  circ.  mils. 

In  our  table  it  shows  the  size  of  wire  for  this  number  of  circ. 
mils,  to  be  00. 

To  check  this  and  determine  exactly  the  volts  lost  in  this  cir- 
cuit by  using  No.  00  wire  use  formula  B,  as  follows : 

10,486  x  152.7amperes=  1601212  —-  133079  circ.  mils.  = 
12.03  volts  lost. 

Suppose  it  is  desired  to  distribute  1,000  lamps  at  a  distance  of 
1950  feet  by  3-wire  system,  viz.,  220  volts,  with  a  loss  of  10  per 
cent. 

Using  formula  A, 

1950  feet  x  2  x  10.7  (see  table)  ==  41730. 
1000  lamps  on  220  volt  system  =291  amperes. 
(See  table  No.    5  for  amperes  per  lamp,  and  multiply  by 
1000.) 


168  HANDBOOK   ON    ENGINEERING. 

10  per  cent  on  220  volt  system  =  24.44   volts   lost.     (See 

table  No.  4.) 
41730    x     291     amperes  =  12143430  -;-  24.44     volts     lost 

=  496867  circ.  mils. 
500000  circ.    mils.,  the  nearest  commercial  size,  should  be 

used. 
Check  this  as  before  by  formula  B. 

41730   x    291    amperes  ==  12 143430  -=-  500000    circ.  mils. 

=  24.29  volts  lost. 

Suppose  we  wish  to  deliver  100  h.  p.  to  a  500  volt  motor,  at 
a  distance  of  4850  feet  with  10  per  cent  loss : 
Again  using  formula  A, 

4850  feet  x  2  x  10.7  =  103790. 

100  h.  p.  at  500  volts  =  160  amperes.     (See  table  No.  3.) 

10  per  cent  loss  on  500  volts    system  =55. 5    volts.     (See 

table  No.  4.) 

103790  x  160  amperes  =  16606400  -f-  55.5    volts  =  299215 
circ.  mils. 

30000  circ.  mils,  cable  should  be  used. 
Check  this  as  before  by  formula  B. 

103790    x    160  amperes  =  16606400  -f-  300000    circ.  mils. 

=  55.35  volts  lost. 

To  ascertain  how  many  amperes  could  be  carried  to  a  distance 
of  4850  feet  with  500  volts  with  ten  per  cent  loss,  use  formula  C  : 
4850  feet  x  2  x  10.7  =  103790. 
10  per  cent  loss  on  500  volts  system  =  55.5  volts. 
300000  circ.  mils,  x  55.5  volts  lost-;-  103790  =  160.42  am- 
peres, which  as  will  appear  by  reference  to  table  No.   3, 
will  permit  the  use  of  100  h.  p.  motor. 


HANDBOOK  ON  ENGINEERING. 


169 


TABLE  No.  3. 


Amperes  per  Motor. 


H.  P. 

Per  Cent 
Efficiency 

Watts. 

VOLTS. 

110 

115 

120 

i 

65 

860 

7.82 

7.48 

7.17 

i 

65 

1148 

10.4 

9.98 

9.57 

2 

66 

2295 

20.8 

20.0 

19.1 

2h 

75 

2487 

22.6 

21.6 

20.7 

H 

75 

3480 

31.6 

30.3 

29.0 

5 

80 

4662 

42.4 

40.5 

38.8 

74 

80 

6994 

63.6 

60.8 

68.3 

10 

85 

8776 

79.8 

76.3 

73.1 

15 

85 

13166 

120. 

114. 

110. 

20 

90 

16578 

151. 

144. 

138. 

25 

90 

20722 

188. 

180. 

173. 

80 

90 

24867 

226. 

216. 

207. 

40 

90 

33155 

301. 

288. 

276. 

50 

90 

41444 

377. 

360. 

345. 

70 

90 

68022 

628. 

605. 

484. 

90 

90 

74600 

678. 

649. 

622. 

100 

93 

80215 

729. 

697. 

668. 

125 

93 

100269 

912. 

872. 

836. 

150 

93 

120323 

1094. 

1046.  - 

1003. 

The  above  table  Js  arranged  to  show  the  amperes  per  motor  at  dif * 
ierent  voltages  lor  several  sizes  of  motors  at  efficiencies  obtained  in 
ordinary  practice. 


170 


HANDBOOK  ON  ENOINEERING. 


TABLE  Ko.8. 


Amperes  per  Motor. 


VOLTS, 


125 

220 

250 

500 

525 

550 

6.88 

8.91 

3.44 

1.72 

1.64 

1.56 

9.18 

5.22 

4.59 

2.30 

2.19 

2.09 

18.4 

10.4 

9.18 

4.59 

4.37 

4.17 

19.9 

11.8 

9.95 

^197 

4.74 

4.52 

27.8 

15.8 

13.9 

v6.96 

6.63 

6.33 

87.3 

21.2 

18.6 

9.32 

8.88 

8.48 

66.0 

31.8 

28.0 

14.0 

13.3 

12.7 

70.2 

39.9 

85.1 

17.6 

16.7 

16,0 

105. 

59.8 

52.6 

26.3 

25.1 

23.9 

188. 

75-4 

66.3 

33.2 

31.6 

SO.l 

166. 

94.2 

82.9 

41.4 

39.5 

37.  7 

199. 

113* 

99.4 

49.7 

47.4 

45.2 

265. 

151. 

1,33. 

66.3 

63.2 

60.  a 

382. 

188. 

166. 

82.9 

79.0 

75.4 

464. 

264. 

232. 

116. 

111. 

106. 

597. 

339. 

298. 

149. 

142. 

136. 

642. 

365. 

321. 

160. 

153. 

146. 

802, 

456. 

401. 

200. 

191. 

182. 

963, 

547, 

481. 

241. 

229. 

219. 

The  above  table  is  arranged  to  show  the  amperes  per   motor   at 
different  voltages  for  Several  01338  of  motors  at  efficiencies  QbtainecMn 


HANDBOOK  ON  ENGINEERING. 


171 


Volts-  Lost  at  Different  Per  Cent  Drop* 

Voltage  at  Lamp  or  Distribution  Point,  Top  Row. 
TABLE  No.  4. 


VOLTS 

52 

75 

ICO 

110 

220 

400 

\% 

.261 

.376 

.502 

.552 

1.10 

2.01 

\% 

.525 

.757 

1.01 

1.11 

2.22 

4.04 

\Vh 

.787 

1.14 

1,52 

1.67 

3.35 

6.09 

2% 

1.06 

1.53 

2.04 

2.24 

4.48 

8.10 

2*% 

1.33 

1.92 

2.56 

2.82 

5.64 

10.25 

3% 

1.61 

2.31 

3.09 

3.40 

6.80 

12.37 

4% 

2.16 

3.12 

4.16 

4.58 

9.16 

16.06 

b% 

2.73 

3.94 

5.26 

5.78 

11.57 

21.05 

f>%' 

3.31 

4.78 

6.38 

7.02 

14.04 

25.53 

1% 

3.91 

5.C4 

7.52 

8.27 

16.55 

30.10 

•*% 

4.52 

6o52 

8.69 

9.56 

19.13 

34.78 

9% 

5.14 

7.41 

9.89 

10.87 

21.75 

39.56 

10% 

5.77 

8.33 

11.11 

12.22 

24.44 

44.44 

12% 

7.09 

10.22 

13.63 

14.99 

29.99 

54.54 

13% 

7.76 

11.10 

14.04 

16.43 

32.87 

59.76 

14% 

8.46 

12.20 

16.27 

17.90 

35.81 

65.1 

15% 

9.17 

13.23 

17.64 

19.41 

38.82 

70.5 

20% 

13. 

18.75 

25. 

27.50 

55. 

100, 

25% 

17.33 

25. 

33.33 

36.66 

73.33 

133. 

The  above  table  shows  the  loss  In  voltage  between  dynamos  and 
distribution  point  at  different  per  cents  and  for  various  voltages. 


172 


HANDBOOK  ON   ENGINEERING. 


Yolts  Lost  at  Different  Per  Cent  Drop. 

Voltage  at  Lamp  or  Distribution  Point.  Top  Row. 
TABLE  No.  4. 


500 

600 

800 

1000 

1200 

2000 

2.51 

3  01 

402 

5  02 

C.03 

10.05 

6  06 

6.66 

8.08 

10.10 

12.12 

20.2 

7.61 

9.13 

12.1 

152 

18.2 

30.4 

10  2 

12.2 

,    16  3 

204 

24.4 

40.8 

12  8 

15  3 

20.5 

25.6 

30.7 

51.2 

15.4 

18.5 

24.7 

30.9 

37.1 

61.8 

20.8 

24.9 

33.3 

41.6 

49  9 

83.3 

26.3 

31.5 

42.1 

52.6 

63.1 

105. 

81.9 

38.2 

51. 

63.8 

76.  5 

127. 

37.6 

45.1 

60.2 

752 

90.3 

150. 

43.4 

62.1 

69.5 

86.9 

104. 

173. 

49.4 

59.3 

79.1 

98.9 

118. 

197. 

555 

66.6 

88  8 

111. 

133. 

222. 

61.7 

71.1 

98  8 

123. 

148. 

247. 

68.1 

81.8 

109. 

136. 

163. 

272. 

74  7 

89.6 

119. 

149. 

179. 

298. 

81.3 

97.6 

130. 

162. 

195. 

325. 

88.2 

105. 

141. 

176. 

211. 

352, 

125. 

150. 

200. 

250. 

300. 

400. 

166. 

200. 

266. 

333. 

400. 

666. 

,By  adding  the  volts  given  in  the  table  to  the  voltage  at  motor  or  lamp 
the  result  shows  the  voltage  necessary  at  dynamo  for  voltage  required 
at  point  of  distribution, 


HANDBOOK  ON  ENGINEERING. 


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174 


HANDBOOK  ON  ENGINEERING. 


APPROXIMATE  WEIGHT  AND  MEASUREMENT  Of  "0.  K."  TRIPLE   5RAIDED 
TABLE  No.  6  WEATHERPROOF   COPPER  WIRE. 


B.  &  S.  Gauge  No. 

Feet  Per  Pound 

Pounds  Per  1000  Ft. 

Pounds  Per  Mile 

0000 

1.30 

767 

4050 

000 

1.59 

629 

3320 

00 

2.02 

495 

2610 

0 

2.45 

407 

2150 

1 

3.22 

310 

1640 

2 

4.00 

250 

1320 

3 

5.03 

199 

1050 

4 

6.10 

164 

865 

5 

7.43 

135 

710 

6 

9.00 

in 

587 

8 

13.54 

74 

390 

10 

18.85 

53 

280 

12 

28.54 

35 

185 

14 

40.61 

25 

130 

16 

60.00 

17 

88 

18 

75.43 

13 

70 

TABLE   OF   MAGNETIZING  FORCE   IN   AMPERE   TURNS   REQUIRED   PER 
INCH  OF   LENGTH   OP    MAGNETIC   CIRCUIT. 


Magnetic    Den- 
sity per  Square 
inch    in 
Gausses. 

MAGNETIZING    FORCE    IN    AMPERE   TURNS 

Air. 

Cast  Iron. 

Steel. 

Wrought  Iron. 

5,000 

1,567 

3.80 

2.85 

1.50 

10,000 

3,134 

5.35 

4.25 

2.40 

15,000 

4,701 

6.80 

5.35 

3.20 

20,000 

6,268 

8.00 

6.30 

3.90 

25,000 

7,835 

10.30 

7.50 

4.60 

30,000 

9,402 

16.20 

8.80 

5.30 

35,000 

10,969 

28.70 

10.20 

5.90 

40,000 

12,536 

49.00 

11.70 

6.50 

45,000 

14,103 

80.00 

13.40 

7.10 

50,000 

15,670 

160.00 

15.40 

8.20 

55,000 

17,237 

240.00 

17.80 

9.50 

60,000 

18,804 

350.00 

20.70 

11.00 

65,000 

20,371 

490.00 

24.10 

13.50 

70,000 

21,938 

650.00 

28.00 

17.00 

75,000 

23,505 



34.00 

21.80 

80,000 

25,072 



42.00 

27.50 

HANDBOOK  ON  ENGINEERING. 


Table  Showing  Difference  Between  Wire  Ganges  in  Decimal  Parts 
TABLE  No.  1  of  an  Inch. 


2 

*l 

*3 

6« 
K 

American  or 
Brown  & 

8harpe. 

Birmingham  or 
Stubs'. 

WnshburnA  Moen 
Manufacturing 
Co.,  Worcester, 
Mass. 

Trenton  Iron  Co., 
Trenton.  N.  J. 

Mew  British. 

1 

la 

52 
3* 

fia 

22 

o« 

No.  of  Wire. 
41 

000000 

.46 

000000 

00000 

.43 

.46 

00000 

0000 

.46 

.454 

.393 

.4 

.4 

0000 

000 

.40964 

.425 

.362 

.36 

.372 

000 

00 

.3648 

.38 

.331 

.33 

.348 

00 

o 

.32495 

.34 

.307 

.305 

.324 

0 

1 

.2893 

.3 

.283 

.285 

.3 

I 

2 

.25763 

.284 

.263 

.265 

.276 

2 

8 

22942 

.259 

.244 

.245 

.252 

3 

.20431 

.238 

.225 

.225 

.232 

4 

5 

.18194 

.22 

.207 

.205 

.212 

5 

6 

.16202 

.203 

.192 

.19 

.192 

6 

7 

.14428 

.18 

.177 

.175 

.176 

1 

8 

.12849 

.165 

.162 

.16 

.16 

8 

9 

.11443 

.148 

.148 

.145 

.144 

9 

10 

.10189 

.134 

.135 

.13 

.128 

10 

11 

.090742 

.12 

.12 

.1175 

.116 

11 

12 

.080808 

.109 

.105 

.105 

.104 

12 

13 

'.071961 

.095 

092 

.0925 

.092 

13 

14 

15 
16 
17 
18 
19 

20 
21 
22 
.23 
24 

25 
26 
27 
28 
29 

30 
31 
•32 
83 
84 

36 

•86 
37 

.064084 

.057068 
.05082 
.045257 
.040303 
.03589 

.031961 
.028462 
.025347 
.022571 
.0201 

.0179 
.01594 
,014195 
.012641 
.011267 

,010025 
.008928 
.00795 
.00708 
.006304 

.005614 
.005 

.004453 

.083 

.072 
.065 
.058 
.049 
.042 

.035 
.032 
.028 
.025 
.022 

.02 
.018 
.016 
.014 
.013 

.012 
.01 
.009 
.008 
•007 

.005 
.004 

.08 

.072 
.063 
.054 
.047 
.041 

,035 
.032 
.028 
.025 
.023 

.02 
.018 
.017 
.016 
.015 

.014 
,0135 
.013 
.011 
.01 

.0095 
009 
.0085 

.08 

.07 
.061 
.0525 
.045 
.039 

.034 
.03 
.27 
.024 
.0215 

.019 
.018 
.017 
.016 
.015 

.014 
.013 
.012 
.011 
.01- 

.009 
.008 
.00125 

.08 

.072 
.064 
.056 
,048 
.04 

.036 
.032 
.028 
.024 
.022 

.02 
.018 
.0164 
.0148 
.0136 

.0124 
.0116 
.0108 
.01 

.0092 

.0084 
.0076 
.0068 

083 

,072 
.065 
.058 
.049 
.04 

.035 
0315 
.0295 
.027 
.025 

.023 
.0205 
.01875 
.0165 
.0155 

.01375 
.01225 

.01125 
.01025 
.0095 

,009 
.0075  t 
.0965 

14 

15 
16 
17 
18 
19 

20 
21 

22 
23 
24 

25 
26 
27 
28 
29 
30 
31 
32 
33 
34 
35 
36 
37 

38 

.003965 

,XX)8 

.0065 

.006 

.00575 

38 

89 
40 

.003531 
.003144 

•  ; 

.0075 
.007 

.00575 
.005   j 

.0052 
.0048 

.005 
.0045 

39 
46 

170 


HANDBOOK  ON  ENGINEERING. 


Weather- 
proof in- 
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HANDBOOK  ON  ENGINEERING.  177 


THE  STEAM  ENGINE. 

CHAPTER  XI. 
THE  SELECTION  OF  AN  ENGINE. 

There  are  so  many  conflicting  statements  in  regard  to  the 
merits  and  demerits  of  the  several  engines  placed  in  the  market 
that  one  is  often  confused  in  judgment,  and  scarcely  knows  how 
to  proceed  in  the  matter  of  selection. 

It  is  easy  to  advise  that  "  When  you  are  ready  to  buy,  select 
the  best  engine,  for  in  the  long  run  the  best  is  the  cheapest." 
No  one  would  pretend  to  deny  this  as  a  general  rule,  yet  there  are 
circumstances  which  so  materially  modify  this  rule  that  it  would 
seem  to  a  casual  observer  to  be  entirely  set  aside.  There  are 
localities  in  which  the  price  of  fuel  is  so  low  that  it  scarcely  war- 
rants the  doubling  of  the  price  on  an  engine  to  save  it ;  and  in 
such  localities  the  owners  usually  want  an  engine  of  the  very 
simplest  construction ;  hence,  they  almost  invariably  select  an 
ordinary  slide  valve  engine  with  a  throttling  governor.  This 
selection  is  made  for  several  reasons,  among  which  are  low  first 
cost,  simple  in  detail,  remoteness  from  the  manufacturer  or  from 
repair  shops. 

For  small  powers  in  which  it  is  desirable  that  the  investment 
be  as  low  as  consistent  with  commercial  success,  the  engine 
selected  should  be  fitted  with  a  common  slide  valve ;  this  will  in 
general  apply  to  all  engines  having  cylinders  eight  inches  or  less 
in  diameter. 

If  upon  a  thorough  canvass  of  the  situation,  it  then  be  thought 
advisable  to  employ  an  automatic  cut-off  engine,  the  next  ques- 
tion would  probably  be  whether  it  shall  be  fitted  with  a  positive 
or  some  one  of  the  various  "drop"  movements  now  in  the 
market. 

12 


178  HANDBOOK  ON    ENGINEERING. 

For  the  smaller  sizes,  say  8  to  24  inches  diameter  of  cylinder 
it  will  perhaps  be  found  more  desirable  to  use  an  automatic  slide 
cut-off,  of  which  there  are  now  several  varieties  offered  through 
the  trade.  This  style  of  engine  has  the  advantage  of  being  low- 
priced,  efficient  and  economical. 

Small  engines  are  usually  required  to  run  at  pretty  high 
speed  ;  there  is  a  very  decided  advantage  in  this  on  the  score  of 
economy,  as  a  small  engine  running  at  a  high  speed  will  be  quite 
as  efficient  as  a  large  engine  running  at  a  slow  speed,  with  the 
further  advantage  that  the  former  will  not  cost  in  original  outlay 
more  than  about  two-thirds  of  the  latter,  while  the  cost  of  operat- 
ing will  be  no  greater  per  indicated  horse-power. 

The  slide  valve  is  still  used  to  the  almost  total  exclusion  of  all 
other  kinds  in  locomotives.  It  is  doubtful  whether  a  better  valve 
for  that  particular  use  can  be  devised.  It  is  simple,  efficient',  and 
readily  obeys  the  action  of  the  link  when  controlled  or  adjusted 
by  the  engineer.  For  portable  engines  and  the  smaller  stationary 
engines  it  leaves  little  to  be  desired  in  point  of  simplicity. 

One  objection  to  a  slide  valve  is  that  it  cannot  readily  be  made 
to  cut  off  steam  at,  say,  half -stroke  or  less,  without  interfering 
with  the  exhaust.  In  ordinary  practice  f  to  f  seems  to  be  where 
most  slide  valves  cut  off  as  a  minimum,  perhaps  |  would  repre- 
sent nearer  the  actual  average  conditions. 

It  can  easily  be  shown  that  this  is  very  wasteful  of  steam,  and 
consequently  not  economical  in  fuel ;  but  as  there  are  cases  in 
which  the  loss  in  fuel  is  fully  gained  by  other  advantages,  the 
ordinary  slide  valve  will,  in  all  probability,  continue  to  be 
used. 

High  speed  engines* — The  general  tendency  seems  now  to  be 
in  the  direction  of  a  horizontal  engine  with  a  stroke  of  medium 
length  having  a  rapid  piston  speed  and  a  rapid  rotation  of  crank 
shaft,  rather  than  a  longer  stroke  with  a  less  rate  of  revolution. 
This  rapid  movement  of  piston  and  crank  shaft  permits  the  use  of 


HANDBOOK     ON     ENGINEERING.  179 

small   fly-wheels  and  driving  pulleys,  and  thus  very  materially 
reduces  the  cost  of  an  engine  for  a  given  power. 

To  illustrate  this,  it  may  be  said  that  a  16  x  48  inch  engine 
using  steam  at  80  Ibs.  pressure  and  cutting  off  J  stroke,  running 
at  the  rate  of  60  revolutions  per  minute,  may  be  replaced  by 
an  engine  having  a  13  x  24  inch  cylinder,  running  at  the  rate  of 
200  revs,  per  minute,  the  pressure  of  steam  and  point  of  cut- 
ting off  remaining  the  same,  both  engines  being  non-condensing 
and  representing  the  best  examples  of  their  kind.  The  differ- 
ence between  60  and  200  revolutions  per  minute  in  millwright 
work  is  very  great,  but  there  is  a  constantly  growing  demand  for 
an  engine  which  shall  meet  such  a  requirement  whenever  it 
shall  present  itself  ;  by  this  it  is  not  to  be  understood  an  engine 
which  shall  be  used  at  either  speed  indiscriminately,  but  rather  a 
type  of  engine  which  shall  be  economical  in  fuel,  and  shall  be  of 
a  kind  by  which  the  rate  of  revolution  may  be  such  as  to  suit  the 
millwright's  work  without  loss  of  economy  in  working,  and  with- 
out excessive  outlay  for  the  engine  itself  in  proportion  to  power 
developed. 

Slow  speed  engines  are  designed  and  built  from  a  standpoint 
entirely  different  from  that  of  high  speed  engines  ;  in  the  former 
case  the  reciprocating  parts  are  made  as  light  as  possible,  con- 
sistent with  safety.  The  fly-wheel  is  large  in  diameter  and  made 
with  a  very  heavy  rim,  especially  is  this  the  case  with  auto- 
matic cut-off  engines  of  long  stroke  and  slow  revolution  of  crank 
shaft. 

In  High  speed  engines  the  reciprocating  parts  are  often  of 
great  weight,  in  order  to  insure  the  utmost  smoothness  of  running. 
The  piston  and  cross-head  are  made  of  unusual  weight  that  at  the 
bginning  of  the  stroke  they  may  require  a  large  part  of  the  steam 
pressure  to  set  them  in  motion  ;  this  absorbing  of  power  at  the 
beginning  of  the  stroke  is  for  the  purpose  of  temporarily  storing 
it  up  in  the  reciprocating  parts  that  it  may  be  given  off  at  the 


180  HANDBOOK    ON     ENGINEERING. 

later  portions  of  the  stroke,  by  imparting  their  momentum  to  the 
crank ;  thus  at  the  beginning  of  the  stroke,  these  reciprocating 
parts  act  as  a  temporary  resistance,  but  once  in  motion  they  tend 
by  their  inertia  to  equalize  the  pressure  on  the  crank  pin,  and  so 
produce  not  only  smooth  running,  but  a  very  uniform  motion. 

Results  to  be  obtained  in  practice* — The  best  automatic  non- 
condensing  engines  furnish  an  indicated  horse-power  for  about 
three  pounds  of  good  coal,  depending  somewhat  upon  the  fitness 
of  the  engine  for  the  work  and  the  quality  of  the  coal.  With  a 
condenser  attached,  a  consumption  as  low  as  two  pounds  has  been 
reported,  but  this  is  an  exceptional  result,  2J  pounds  may  be 
quoted  as  good  practice.  The  larger  the  engine  the  better  the 
showing,  as  compared  with  smaller  engines. 

For  ordinary  slide  valve  engines,  the  coal  burned  per  indicated 
horse-power  will  vary  from  9  to  12  Ibs.,  for  the  sake  of  illustra- 
tion, we  will  say  10  Ibs.,  and  that  the  engine  is  of  such  size  as 
would  require  for  a  year's  run  $3,000  worth  of  coal;  now  an 
ordinary  adjustable  cut-off  engine  with  throttling  governor,  ought 
to  save  at  least  half  that  amount  of  coal,  or  say  $1,500  per  year  ; 
if  the  best  automatic  engine  were  employed  using  2  J  Ibs.  of  coal 
per  horse-power,  a  further  saving  of  $750  per  year  could  be 
effected,  or  between  the  two  extremes  $2,250  per  year  in  saving 
of  coal,  without  interfering  in  anyway  with  the  power,  with  the 
exception  perhaps,  that  the  automatic  engine  will  furnish  a  better 
power  than  the  former  engine.  It  is  easy  to  see  that  it  is  true 
economy  to  buy  the  best  engine  and  pay  the  extra  cost  of  con- 
struction, if  the  saving  of  fuel  is  an  element  entering  into  the 
question  of  selection. 

The  cost  of  an  engine  for  any  particular  service  is  always  to 
be  taken  into  consideration,  for  it  is  possible  to  contract  for  a 
certain  saving  of  coal  at  too  high  a  price,  not  simply  when  paid 
out  as  the  original  purchase  money,  but  with  this  economy  of 
fuel,  the  purchaser  may  have  many  vexatious  and  damaging 


HANDBOOK    ON   ENGINEERING.  181 

delays  caused  by  the  breaking  of  the  automatic  mechanism  of  the 
engine.  All  such  delays,  which  would  not  have  occurred  to  an 
ordinary  or  simpler  engine,  are  to  be  charged  against  any  saving 
credited  to  the  engine,  which  failed  in  producing  a  regular  and 
constant  power.  Take  a  flouring  mill  for  example,  producing  400 
barrels  per  day  ;  it  is  easy  to  see  how  a  single  day's  stoppage 
would  interfere  with  the  trade  and  shipment  by  the  proprietors, 
yet  it  would  require  a  very  small  break  in  an  engine  that  would 
require  less  than  a  day  for  repairs. 

This  does  not  argue  against  high  grade  engines,  but  the  pur- 
chaser should  be  certain  that  the  engine  when  once  on  its  founda- 
tions shall  be  as  free  from  dangers  of  this  kind  as  any  other 
engine  of  similar  economy. 

There  are  engines,  which,  from  their  peculiar  construction 
appear  to  be  very  complex,  and  this  objection  is  often  urged 
against  them,  while  the  fact  is  the  complexity  is  apparent  rather 
than  real.  Take  the  Corliss  engine,  for  example  ;  it  is  doubtful 
whether  there  is  another  automatic  cut-off  engine  in  successful 
use  in  this  or  any  other  country  which  has  cost  less  for  repairs 
during  the  last  ten  or  twenty  years.  It  is  true  it  contains  a  great 
many  separate  pieces  in  the  valve  mechanism,  but  the  pieces 
themselves  are  simple,  durable,  easily  accessible  and  always  in 
sight.  These  several  parts  are  not  liable  to  excessive  wear,  but 
such  as  there  is  can  be  readily  adjusted. 

The  engines  to  be  preferred  are  those  in  which  the  valve 
adjusting  mechanism  is  outside  of  the  steam  chest  and  which  is  in 
plain  sight  at  all  times  when  the  engine  is  in  motion. 

Location  of  engine* — This  will  depend  upon  circumstances, 
but  it  is  far  from  true  economy  to  place  an  engine  in  a  dark  cellar, 
or  in  some  inconvenient  place  above  ground.  The  engine  as  the 
prime  mover,  should  have  all  the  care  and  attention  which  may  be 
needed  to  insure  regular  and  efficient  working. 

Machinery  in  the  dark  is  almost  sure  to  be  neglected.      If  the 


182  HANDBOOK    ON    ENGINEERING. 

design  of  the  building,  or  the  nature  of  the  business,  is  such  that 
the  engine  must  be  located  underground,  there  should  be  some 
provision  for  letting  in  the  daylight ;  the  extra  expense  incurred 
will  soon  be  saved  by  the  order,  cleanliness  and  fewer  repairs 
required. 

The  engine  should  always  be  close  to,  but  not  in  the  boiler 
room.  Many  a  high-priced  engine  has  had  its  days  of  usefulness 
shortened  by  the  abrasive  action  of  fine  ashes  and  coal  dust 
coming  in  contact  with  the  wearing  surface.  There  should  always 
be  a  wall  or  tight  partition  between  the  engine  and  fire  room. 

The  foundations  for  an  engine  should  be  large  and  deep. 
Too  many  manufacturers  in  marking  dimensions  of  foundation 
drawings  for  engines,  make  them  altogether  too  shallow.  The 
stability  of  an  engine  depends  more  on  the  depth  than  on  the 
breadth  of  the  foundations.  Stone  should  be  used  for  founda- 
tions rather  than  brick,  but  if  the  latter  must  be  used  they  should 
be  hard  burned  and  laid  in  a  good  cement  rather  than  a  lime 
mortar.  If  the  bottom  of  the  pit  dug  for  the  engine  foundation 
be  wet,  or  the  soil  uncertain  in  its  stability,  it  is  a  good  plan  to 
make  a  solid  concrete  block  about  a  foot  and  a  half  thick,  on 
which  the  foundation  may  be  continued  to  the  top.  If  such  a 
concrete  block  be  made  with  the  right  kind  of  cement  it  will  be 
almost  as  hard  and  solid  as  a  whole  stone. 

The  most  economical  engine  is  the  one  in  which  high  pressure 
steam  can  be  used  during  such  portion  of  the  stroke  as  may  be 
necessary,  then  qickly  cut  off  by  a  valve,  which  shall  not  inter- 
fere with  the  exhaust  at  the  opposite  end  of  the  cylinder,  and 
allow  the  steam  to  expand  in  the  cylinder  to  a  pressure,  which 
shall  not  fall  below  that  necessary  to  overcome  the  back  pressure 
on  the  piston.  In  general,  the  most  successful  cut-off  engines 
use  the  boiler  pressure  for  a  distance  of  one-fifth  to  three-eighths 
of  the  stroke  from  the  beginning;  at  this  point  the  steam  is  cut 
off  and  allowed  to  expand  throughout  the  balance  of  the  stroke. 


HANDBOOK    ON  ENGINEERING 


183 


The  gain  by  expansion  consists  in  the  admission  of  steam  at  a 
pressure  much  above  the  average  required  to  do  the  work,  and 
allowing  it  to  follow  but  a  small  portion  of  the  stroke,  then  ex- 
panding to  a  lower  than  the  average  pressure  at  the  end  of  the 
stroke.  The  mean  effective  pressure  on  the  piston  is  that  by 
which  the  power  of  the  engine  is  measured,  hence,  it  follows  that 
the  higher  economy  is  to  be  reached,  other  things[being  equal, where 
the  mean  effective  pressure  on  the  piston  is  highest  when  com- 
pared with  the  terminal  pressure, or  the  pressure  at  the  end  of  the 
stroke.  In  order  to  get  this,  a  high  initial  pressure  is  used  ;  the 
steam  follows  as  short  a  distance  as  possible  to  keep  the  motion 
regular  under  a  load,  and  then  expanding  down  to  as  near  tho 
atmospheric  pressure  as  possible. 

The  following  table  exhibits  at  a  glance  the  performance  of  a 
non-condensing  engine  cutting  off  at  different  portions  of  the 
stroke.  The  initial  pressure  of  steam  being  in  each  case  eighty 
pounds  per  square  inch. 

CUT-OFF    IN    PARTS  OF  THE    STROKE. 


1 
10 

2 

10 

3 
10 

4 

To 

5 

To 

Mean  effective  pressure  . 

18 

35 

48 

.57 

65 

Terminal  pressure  .     .     . 

11 

20 

30 

39 

48 

Pounds  water  per  h'r  per 
H.  P  

27 

24 

25 

27 

28 

Fractions  are  omitted  in  the  above  table  and  the  nearest  whole 
number  given. 

Governor- — Any  automatic  device  by  which  the  speed  of  an 
engine  is  controlled  may  properly  be  called  a  governor.  There 


184  HANDBOOK    ON    ENGINEERING. 

are  now  two  distinct  methods  by  which  the  steam  supplied  to  an 
engine  is  thus  brought  under  control.  The  first  is  usually  applied 
to  side  valve  engines  having  a  fixed  cut-off,  and  consists  in  the 
adjustment  of  a  valve  by  which  the  pressure  of  steam  in  the 
cylinder  is  increased  or  diminished  in  order  to  maintain  a  con- 
stant rate  of  revolution  with  a  variable  load.  The  second  device 
consists  in  a  mechanism  by  which  the  whole  boiler  pressure  is 
admitted  to  the  cylinder,  which  is  allowed  to  follow  the  piston  to 
such  portion  of  the  stroke  as  will  maintain  a  regular  rate  of  revo- 
lution ;  the  steam  is  then  suddenly  cut  off  at  each  half  revolution 
of  the  engine,  thus  furnishing  a  greater  or  less  volume  of  steam  at 
a  constant  pressure.  Neither  of  these  two  varieties  of  governors 
will  act  until  a  change  in  the  rate  of  revolution  of  the  engine 
occurs,  and  this  change  will  either  admit  more  or  less  steam  as  it 
is  slower  or  faster  than  that  for  which  the  governor  is  adjusted. 
The  commonest  form  of  a  governor  consists  of  a  vertical  shaft  to 
which  are  hinged  two  arms  containing  at  their  lower  ends  a  ball 
of  cast  iron ;  as  the  shaft  revolves  the  balls  are  carried  outward 
by  the  action  of  what  is  commonly  called  centrifugal  force ;  the 
greater  the  rate  of  revolution  the  farther  will  the  balls  be  carried 
outward ;  advantage  is  taken  of  this  property  to  regulate  the  ad- 
mission of  steam  to  the  engine.  The  action  of  the  balls  and  that 
of  the  valve  include  two  distinct  principles  and  should  be  consid- 
ered separately ;  an  excellent  valve  may  be  manipulated  by  an 
indifferent  governor  and  so  produce  unsatisfactory  results  ;  on  the 
other  hand,  the  governor  mechanism  may  be  satisfactory  in  its 
operation,  but  being  connected  with  a  valve  not  properly  balanced , 
is  likely  to  cause  a  variable  rate  of  revolution  in  the  engine. 

Fly- wheel* — The  object  in  attaching  a  fly-wheel  to  an  engine 
is  to  act  as  a  moderator  of  speed.  The  action  of  the  steam  in  the 
cylinder  is  variable  throughout  the  stroke,  against  which  the  rev- 
olution of  a  heavy  wheel  acts  as  a  constant  resistance  and  limits 
the  variations  in  speed  by  absorbing  the  surplus  power  of  the  first 


HANDBOOK  ON  ENGINEERING.  185 

portion  of  the  stroke,  and  giving  it  out  during  the  latter  portion. 
The  fly-wheel  is  simply  a  reservoir  of  power,  it  neither  creates  nor 
destroys  it,  and  the  only  reason  why  it  is  attached  to  an  engine  is 
to  simply  regulate  the  speed  between  certain  permitted  variations, 
which  are  necessary  to  cause  the  governor  to  act,  and  to  equalize 
the  rate  of  revolution  for  all  portions  of  the  stroke,  thus  con  vert- 
ing a  variable  reciprocating  motion  into  a  constant  rotary  one.  It 
is  considered  good  practice  to  make  the  diameter  of  the  fly-wheel 
four  times  the  length  of  the  stroke  for  ordinary  engines,  in  which 
the  stroke  is  equal  to  twice  the  diameter  of  the  cylinder.  This 
may  be  taken  as  a  fair  proportion  in  engine  building,  and  furnishes 
a  wheel  sufficiently  large  to  equalize  the  strain  and  reduce  any 
variation  in  speed  to  within  very  narrow  limits,  if  the  engine  is 
supplied  with  a  proper  governor.  The  greater  the  number  of 
revolutions  at  which  the  engine  runs,  the  smaller  in  diameter  may 
be  the  fly-wheel,  and  it  may  also  be  largely  reduced  in  weight  for 
engines  developing  the  same  power. 

Horse-power-  —  By  this  term  is  meant  33,000  pounds  raised 
one  foot  high  in  one  minute.  The  horse-power  of  an  engine  may 
be  found  by  multiplying  the  area  of  the  p.iston  in  square  inches 
by  the  mean  effective  pressure:  this  will  give  the  total 
pressure  on  the  piston ;  multiply  this  total  pressure  by  the 
length  of  the  stroke  of  the  piston  in  feet ;  this  will  give  the 
work  done  in  one  stroke  of  the  piston  ;  multiply  this  product  by 
the  number  of  strokes  the  piston  makes  per  minute,  which  will 
give  the  total  work  done  by  the  steam  in  one  minute  ;  to  get  the 
horse-power,  divide  this  last  product  by  33,000.  From  this 
deduct,  say,  20  per  cent,  for  various  losses,  such  as  friction,  con- 
densation, leakage,  etc. 

CARE  AND  MANAGEMENT  OF  A  STEAfl  ENGINE 

It  is  to  be  supposed  to  begin  with  that  the  engine  is  correctly 
designed  and  well  made,  and  that,  after  a  suitable  selection  of  an 


186  HANDBOOK  ON  ENGINEERING. 

engine  for  the  work  to  be  done,  nothing  now  remains  except 
proper  care  and  management. 

Lubrication*  —  The  first  and  all-important  thing  in  regard  to 
keeping  an  engine  in  good  working  order  is  to  see  that  it  is 
properly  lubricated.  This  does  not  imply,  neither  is  it  intended 
to  encourage,  the  use  of  oil  to  excess  ;  all  that  is  needed  is  simply 
a  film  of  oil  between  the  wearing  surfaces.  It  is  marvelous  hew 
small  a  quantity  of  oil  is  required  when  of  good  quality  and  con- 
tinuously applied.  There  are  several  self-feeding  lubricators  in 
the  market  which  have  been  tested  for  years  and  area  pronounced 
success;  these  include  crank-pin  oilers,  in  which  the  oscillatory 
motion  of  the  oil  makes  a  very  efficient  self -feeding  device,  the 
flow  being  regulated  by  means  of  an  adjustable  opening  to  the 
crank-pin,  or  in  the  adjustment  of  a  valve  by  which  its  lift  is  reg- 
ulated by  each  throw  of  the  crank ;  and  in  others  by  a  continual 
flow  through  a  suitable  tube  containing  a  wick  or  other  porous 
substance.  For  stationary  engines,  it  is  desirable  that  the  main 
body  of  the  oiler  be  made  of  glass  that  the  flow  of  oil  may  be 
closely  watched  and  adjusted  accordingly.  For  the  reciprocating 
and  rotary  parts  of  the  engine,  a  modification  of  the  above  men- 
tioned oilers  may  be  used.  They  are  of  various  patterns  and 
devices  and  many  of  them  very  good.  It  is  also  a  good  plan  to 
have  some  device  by  which  the  cross-head  at  each  end  of  each 
stroke  will  take  up  and  carry  with  it  a  certain  amount  of  oil ;  for 
the  lower  half  of  the  slide  this  is  not  difficult  to  arrange  ;  for  the 
upper  side  an  automatic  feeder  placed  in  the  middle  of  the  slides 
will  provide  ample  lubrication. 

For  oiling  the  main  bearing  there  should  be  two  separate 
devices,  one  an  automatic  glass  oiler;  and  in  addition,  a  large 
tallow  cup  attached  to  the  cap  of  the  bearing.  This  cup  should 
be  filled  with  tallow  mixed  with  powdered  plumbago ;  the  open- 
ings from  the  bottom  of  the  cup  to  the  shaft  should  be  not  less 
than  quarter  inch  for  small  engines,  and  three-eighths  to  half -inch 


HANDBOOK    ON    ENGINEERING.  187 

for  larger  ones ;  so  long  as  the  main  bearing  runs  cool  the  tallow 
will  remain  in  the  cup  unmelted  ;  but  if  heating  begins,  the  tallow 
will  melt  and  run  down  on  the  surface  of  the  revolving  shaft,  and 
thus  provide  an  efficient  remedy  when  needed.  For  oiling  the 
valves  and  piston,  a  self -feeding  lubricator  should  be  attached  to 
the  steam  pipe ;  this  by  a  continuous  flow  of  oil  will  be  found  not 
only  satisfactory  in  its  practical  working,  but  economical  in  the 
use  of  oil. 

In  selecting  an  oil  for  an  engine,  it  is  in  general  better  to  use  a 
mineral  rather  than  animal  oil,  especially  for  use  in  the  valve 
chest  and  cylinder.  The  objection  to  an  animal  oil,  and  espe- 
cially to  tallow  or  suet,  is  that  it  decomposes  by  the  action  of  heat, 
often  coating  the  surface  of  the  steam  chest,  the  piston  ends  and 
the  cylinder  heads  with  a  deposit  of  hard  fatty  matter ;  or  forms 
into  small  balls  not  unlike  shoemakers'  wax.  There  is  no  such 
decomposition  and  formation  in  connection  with  mineral  oils, 
which  may  now  be  had  of  uniform  quality  and  consistency,  and 
at  much  lower  prices  than  animal  oils. 

The  slide  valve  should  be  kept  properly  set  and  should  be 
examined  occasionally  to  see  that  the  face  and  seat  are  in  good 
condition.  So  long  as  this  is  the  case,  the  valve  mechanism  and 
the  valve  itself  must  be  let  alone  nnd  not  tampered  with, 

The  piston  packing1  will  need  looking  after  occasionally  to 
see  that  it  does  not  gum  up  and  stick  fast,  which  it  is  very  likely 
to  do  when  the  cylinder  is  lubricated  with  tallow  or  animal  oil. 

The  rings  should  fit  the  cylinder  snugly  and  should  be  under 
as  little  tension  as  possible  and  insure  perfect  contact.  If  the 
rings  are  set  out  too  tight  they  are  liable  to  scratch  or  cut  the 
cylinder ;  if  too  loose,  the  steam  will  blow  through  from  one  end 
of  the  cylinder,  past  the  piston  and  into  the  other.  In  adjusting 
the  springs  in  the  piston,  care  must  be  exercised  that  the  adjust- 
ments are  such  as  will  keep  the  piston  rod  exactly  central,  to 
prevent  springing  the  rod,  or  causing  excessive  wear  on  the  stuf- 


188  HANDBOOK    ON    ENGINEERING. 

fing-box.  There  are  several  packings,  which  do  not  require  this 
adjustment,  the  rings  being  narrow,  and  either  expanding  by 
their  own  tension  or  by  means  of  springs  underneath.  The  only 
thing  to  be  done  with  such  a  packing  is  to  keep  it  clean,  and 
when  lubricated  with  a  mineral  oil  this  is  not  a  difficult  matter. 
If  it  groans,  take  rings  out  and  file  sharp  edges  off. 

The  stuffing-boxes  whether  for  the  piston  or  valve-stem  need 
to  be  looked  after  carefully,  and  to  prevent  leaking,  will  require 
tightening  from  time  to  time.  There  are  several  kinds  of  ready- 
made  packings  in  the  market,  containing  rubber,  canvas,  hemp, 
soapstone,  asbestos  and  other  substances  which  form  the  basis  of 
a  good  durable  packing.  These  can  be  had  in  sizes  suitable  for 
all  ordinary  purposes,  and  their  use  is  recommended.  In  the 
absence  of  any  of  these,  a  packing  made  of  clean  manilla  or  hemp 
fiber  will  serve  a  useful  purpose.  Formerly  it  was  the  only  sub- 
stance used,  but  is  being  gradually  superseded  by  the  other  kinds 
mentioned  above.  In  packing  the  small  and  delicate  parts,  such 
as  a  governor  stem,  a  good  packing  is  made  by  pleating  together 
three  or  more  strands  of  cotton  candle-wick.  This  is  soft,  pliable, 
free  from  anything  like  grit,  and  will  not  get  hard  until  soaked 
with  grease  and  baked  into  a  brittle  fiberless  substance  not  easily 
described. 

Crank-pins*  —  There  are  few  things  more  troublesome  to  an 
engineer  than  a  hot  crank-pin,  and  it  is  sometimes  very  difficult 
to  get  at  the  real  reason  why  it  heats.  Among  the  principal  rea- 
sons for  heating  are:  the  main  shaft  is  not  "  square "  with  the 
engine,  or,  that  the  pin  is  not  properly  fitted  to  the  crank ;  or, 
perhaps,  it  is  too  small  in  diameter  —  defects  which  are  to  be 
remedied  as  soon  as  practicable.  Heating  is  often  caused  by  the 
boxes  being  keyed  too  tightly,  or  by  insufficient  lubrication. 
There  are  now  several  good  self -feeding  lubricators  in  the  market 
which  will  supply  the  oil  to  a  crank-pin  continuously  ;  these  are 
recommended  rather  than  the  old  style  of  oil  cup,  which  was 


HANDBOOK    ON    ENGINEERING.  189 

not  only  uncertain,  but  doubtful  in  its  action.  Many  trouble- 
some crank-pins  have  been  cured  of  heating  by  this  simple  matter 
of  constant  lubrication.  When  the  crank-pin  is  rather  small  for 
the  engine  and  the  load  variable,  there  is  a  possibility  of  having 
a  hot  pin  at  any  time  ;  it  is  advisable  to  have  ready  some  simple 
and  effective  expedient  to  be  applied  when  it  does  occur ;  for  this 
there  is  perhaps  nothing  better  and  safer  than  a  mixture  of  good 
lard  oil  and  sulphur. 

Connecting  tod  brasses* — In  quick  running  engines  the 
brasses  should  be  fitted  metal  to  metal ;  or  if  this  is  not  desir- 
able, several  strips  of  tin  or  sheet  brass  should  be  inserted  be- 
tween them  and  keyed  up  tight.  This  gives  a  rigidity  to  a 
joint  which  is  difficult  to  secure  when  the  brasses  have  a  certain 
amount  of  play  in  the  strap.  It  is  a  common  practice  to  bore  the 
brasses  slightly  larger  than  the  pin,  so  that  when  fitted  to  it  the 
hole  shall  be  slightly  oval,  and  thus  permit  a  freer  lubrica- 
tion than  is  secured  by  a  close  fit  around  the  whole  circum- 
ference. 

Knocking*  —  There  are  several  causes  which,  combined  or 
singly,  tend  to  produce  knocking  in  steam  engines.  In  most 
cases  the  difficulty  will  be  found  to  be  in  the  connecting  rod 
brasses  ;  but  whether  in  the  crank-pin  end  or  at  the  cross-head  is 
not  easily  determined  in  all  cases.  A  very  slight  motion  will 
often  produce  a  very  disagreeable  noise ;  the  remedy  is,  in  most 
cases,  very  simple,  and  consists  in  simply  tightening  the  brasses 
by  means  of  the  key  or  other  device  that  may  have  been  pro- 
vided for  their  adjustment.  In  adjusting  a  key  it  is  the  common 
practice  to  drive  it  down  as  far  as  it  will  go,  marking  with  a 
knife  blade  the  upper  edge  of  the  strap,  then  drive  the  key  back 
until  it  is  loose ;  after  which  drive  it  down  again,  until  the 
line  scratched  on  the  key  is  within  J  or  J  inch  of  the  top  of  the 
strap.  The  size  of  the  strap  joint  and  the  judgment  of  the  per- 
son in  charge  must  decide  the  best  distance.  This  may  be  done 


190  HANDBOOK   ON   ENGINEERING. 

at  both  ends  of  the  connecting  rod.  On  starting  the  engine,  the 
cross-head  and  crank-pin  mast  be  carefully  watched,  and  upon 
the  slightest  indication  of  heating,  the  engine  should  be  stopped 
and  the  key  driven  back  a  little  farther.  A  slight  warmth  is  not 
particularly  objectionable,  and  will,  as  a  general  thing,  correct 
itself  after  a  short  run.  Knocking  is  sometimes  occasioned  by 
a  misfit,  either  in  the  piston,  or  crosss-head  and  the  piston-rod. 
These  connections  should  be  carefully  examined,  and  under  no 
circumstances  should  lost  motion  be  permitted  at  either  end 
of  the  piston  rod. 

If  the  means  of  securing  are  such  that  the  person  in  charge  can 
properly  fasten  the  piston  to  the  rod,  he  should  see  that  it  is  kept 
tight ;  if  not,  then  it  should  be  sent  to  the  repair  shop  at  once,  as 
there  is  no  telling  when  an  accident  is  likely  to  overtake  an  engine 
with  a  loose  piston. 

The  connection  between  the  piston-rod  and  cross-head  is  usu- 
ally fitted  with  a  key  and  furnishes  a  ready  means  of  tightening 
the  joint,  if  proper  allowance  has  been  made  for  the  draft  of  the 
key.  In  case  there  has  not,  the  piston-rod  and  cross-head  should 
be  filed  out  so  that  the  draft  of  the  key  will  insure  a  good  tight 
joint  when  driven  down. 

The  main  bearing  should  be  examined  and  if  there  should  be 
too  much  lateral  movement  of  the  shaft,  the  side  boxes  might 
then  be  adjusted  until  the  shaft  turns  freely,  but  has  no  motion 
other  than  a  rotary  one.  The  cap  to  the  main  bearing  should  also 
be  carefully  examined,  as  it  may  need  screwing  down  and  thus 
prevent  an  upward  movement  of  the  shaft  at  each  stroke ;  this 
applies  more  particularly  to  quick  running  engines. 

Engines  which  have  been  in  use  for  some  time  are  likely  to  have 
a  knock  caused  by  the  piston  striking  the  head.  This  is  brought 
about  by  having  a  very  small  clearance  in  the  cylinder  and  in  not 
providing,  by  suitable  liners,  for  the  wear  of  the  connecting  rod 
brasses.  In  case  of  this  kind,  liners  should  be  inserted  behind 


HANDBOOK  ON  ENGINEERING.  191 

the  brasses  in  the  connecting  rod,    or  new  brasses  put  in,  which 
will  restore  the  piston  to  its  original  position. 

Knocking  may  be  caused  by  defects  in  the  construction  of  the 
engine  ;  such,  for  example,  as  not  being  in  line,  the  crank-pin  not 
at  right  angles  to  the  crank,  the  shaft  may  be  out  of  line,  etc. 

Whenever  the  cause  is  one  in  which  it  can  be  shown  that  it  is 
a  constructive  defect,  there  is  but  one  remedy,  and  that  is  the  re- 
placing of  that  part,  or  the  assembling  of  the  whole  until 
perfect  truth  is  had  in  alignment  of  all  the  parts.  This  will 
require  the  services  of  an  experienced  engineer  but  all  improperly 
fitting  pieces  should  be  replaced  by  new  ones  as  a  safeguard 
against  accident,  which  is  likely  sooner  or  later  to  overtake  badly 
fitting  pieces. 

If  the  boiler  is  furnishing  wet  steam,  or  priming,  so  as  to  force 
water  into  the  steam  pipe,  it  will  collect  in  the  cylinder  and  will 
not  only  cause  knocking,  but  on  account  of  its  being  practically 
incompressible  there  is  danger  of  knocking  out  a  cylinder  head, 
bending  the  piston-rod,  or  doing  other  damage  to  the  engine. 
The  cylinder  cocks  should  be  opened  to  drain  any  collected  water 
away  from  the  cylinder. 

Repairs* — Whenever  it  is  necessary  to  make  repairs  the  work 
should  be  done  at  once  ;  oftentimes  a  single  day's  delay  will  in- 
crease the  extent  and  cost  fourfold.  If  an  engine  is  properly 
designed  and  built,  the  repairs  required  ought  to  b.e  very  trivial 
for  the  first  few  years  it  is  run,  if  it  has  had  proper  care.  It  may 
be  said  in  reply  to  this  "true,  but  accidents  will  happen  in  spite 
of  every  care  and  precaution."  That  accidents  do  occur  is  true 
enough ;  that  they  occur  in  spite  of  every  care  and  precaution  is 
not  true.  In  almost  every  case,  accidents  may  be  traced  directly 
back  to  either  a  want  of  care,  negligence,  or  to  a  mistake. 

Fitting  slide-valves* — The  practice  of  fitting  a  slide-valve  to 
its  seat  by  grinding  both  together  with  oil  and  emery,  is  wrong 
and  should  never  be  resorted  to.  The  proper  way  to  fit  the  sur- 


192  HANDBOOK    ON   ENGINEERING. 

faces  is  by  scraping ;  this  insures  a  more  accurate  bearing  to 
begin  with,  and  will  also  be  entirely  free  from  the  fine  grains 
of  emery  which  find  their  way  and  become  imbedded  in  the 
pores  of  the  casting,  and  are  thus  liable  to  cut  the  valve  face  and 
destroy  its  accuracy.  The  scraping  of  the  valve  and  seat  has  a 
beneficial  effect  by  causing  the  removal  of  the  fine  particles  of 
iron,  which  are  loosened  by  the  action  of  the  cutting  tool  in  the 
planing  machine,  and  which  ought  to  be  fully  removed  before  the 
engine  leaves  the  manufacturers'  hands.  Aside  from  this,  it  is 
doubtful  whether  the  scraping  amounts  to  anything  practically, 
for  the  reason  that  the  cylinder  and  valve  are  fitted  cold, and  their 
relative  positions  are  distorted  by  the  action  of  the  heat  of  the 
steam,  once  the  engine  is  in  use.  The  scraping,  which  simply 
renders  the  valve  face  and  seat  smooth  and  hard,  is  all  that  is 
sufficient  to  begin  with,  and  may  be  re-scraped  after  the  valve 
has  been  in  use  a  few  days,  should  it  be  found  necessary, 
which  will  not  often  be  the  case  in  small  and  ordinary  sized 
engines. 

Eccentric  straps  are  likely  to  need  repairs  as  soon  as  any- 
thing about  an  engine.  They  should  be  carefully  watched  at 
all  times.  If  they  are  likely  to  run  hot,  it  is  also  probable 
there  is  more  or  less  abrasion  or  cutting  going  on,  and  if 
prompt  measures  are  not  taken  to  arrest  it,  they  are  likely  to 
cut  fast  to  the  eccentric,  and  a  breakage  is  sure  to  occur. 

When  the  straps  begin  to  heat,  the  bolts  should  be  slackened 
a  little,  and  at  night,  or  perhaps  at  noon,  the  straps  should  be 
taken  off  and  all  cuttings  carefully  removed  with  a  scraper 
(not  with  a  file)  ;  the  rough  surfaces  on  the  eccentric  should 
be  removed  in  the  same  manner. 

The  straps  should  be  run  loose  for  a  few  days,  gradually 
tightening  as  a  good  wearing  surface  is  obtained. 

The  main  bearing,  if  neglected,  is  a  very  troublesome  journal 
to  keep  in  order.  The  repairs  generally  needed  are  those  which 


HANDBOOK  ON  ENGINEERING.  193 

attend  overheating  and  cutting.  The  shaft,  whenever  possible, 
should  be  lifted  out  of  the  bearing,  and  both  the  shaft,  bottom  of 
main  bearing  and  side  boxes,  carefully  scraped  and  made  perfectly 
smooth.  It  sometimes  occurs  that  small  beads  of  metal  project 
above  the  surface  of  the  shaft  which  are  often  so  hard  that  neither 
a  scraper  nor  file  will  remove  them  ;  chipping  is  then  resorted  to 
and  the  fitting  completed  with  a  file  and  fine  emery  cloth. 

Heating*  of  journals.  —  A  very  common  cause  for  the  heating 
of  journals  having  brasses  and  boxes  composed  of  two  halves,  is 
that  both  halves  alter  their  shape  from  causes  attending  their 
wear.  Thus,  most  engineers  will  have  noticed  that,  although 
there  is  no  wear  between  the  sides  of  a  brass  and  the  jaws  of  a 
box,  yet  in  time  the  brass  becomes  a  loose  fit  in  the  box.  Now, 
since  the  sides  of  the  brass  have,  when  fitted,  no  movement  in  the 
box,  it  is  evident  that  this  cannot  have  proceeded  from  wear  be- 
tween those  surfaces,  and  it  remains  t)  find  what  causes  this 
looseness.  Most  engineers  will  also  have  observed  that  though 
the  bottom  or  bedding  surfaces  of  a  brass  and  of  the.  box  may 
have  been  carefully  filed  to  fit  each  other  when  new,  yet  if  in  the 
course  of  time  the  brasses  be  taken  out  and  examined,  and  more 
especially  the  bottom  brass  that  receives  the  weight,  the  file  marks 
will  become  effaced  on  all  parts  where  the  surfaces  have  bedded 
together  well,  the  surface  having  a  dull  bronze  and  condensed 
appearance.  This  is  caused  by  the  vibrations  under  pressure  hav- 
ing condensed  the  metal.  Now,  this  condensation  of  the  metal 
moves  or  stretches  it,  and  causes  the  sides  of  the  brass  to  move 
away  from  the  sides  of  the  box,  and,  consequently,  to  close  upon 
the  journal,  creating  excessive  friction  that  may  often,  and  very 
often  does,  cause  heating.  It  is  for  this  reason  that  on  such 
brasses  the  sides  of  the  brass  boxes  are  by  a  majority  of  engi- 
neers, eased  away  at  and  near  the  joint,  and  it  follows  from  this 
cause  the  same  easing  away  is  a  remedy. 

Governor*  —  It  not  infrequently   occurs  that  after  an  ordinary 


194  HANDBOOK  ON  ENGINEERING. 

throttling  engine  has  been  used  a  few  years,  the  speed  becomes 
variable  to  such  a  degree  that  it  interferes  with  the  proper  run- 
ning of  the  machinery.  This  occurrence  can  generally  be  traced 
directly  to  the  governor.  When  it  does  occur,  the  governor 
should  be  taken  apart  and  thoroughly  examined ;  if  the  needed 
repairs  are  such  as  can  be  easily  made  in  an  ordinary  repair  shop, 
they  should  be  made  at  once ;  if  not,  a  new  governor  should  be 
purchased.  The  price  of  governors  is  now  so  low  that  it  is  better 
and  more  economical  to  buy  a  new  one  than  loose  the  time  and 
pay  the  bills  for  repairing  an  old  one. 

AUTOMATIC  ENGINES. 

In  the  care  and  management  of  this  class  of  engines,  it  is  diffi- 
cult to  say  jnst  what  particular  attention  they  need,  owing  to  the 
variety  of  styles  and  the  peculiarities  of  each.  As  a  rule,  how- 
ever, they  require  first,  to  be  kept  well  oiled  ;  second,  to  be  kept 
clean  ;  third,  to  be  kept  well  packed ;  and  fourth,  to  be  left  alone 
nights  and  Sundays.  There  is  little  doubt  that  there  has  been 
more  direct  loss  rasulting  from  a  ceaseless  tinkering  with  an 
engine  than  results  from  legitimate  wear  and  tear  to  which  the 
engine  is  subjected.  It  is  not  to  be  inferred  from  the  preceding 
remark  that  builders  of  this  class  of  engines  are  infallible ;  it 
might  be  difficult  to  prove  any  such  assertion  in  case  it  was  made ; 
but  it  may  be  said  with  truth,  that  the  engines  of  this  class  now 
.in  the  market  are  carefully  designed,  well  proportioned,  of  good 
materials  and  workmanship,  and  as  examples  of  mechanism  are 
entitled  to  take  very  high  rank.  Engineers  know  of  several 
engines  of  this  class  which  have  not  cost  their  owners  for  repairs 
so  much  as  five  dollars  in  five  years'  constant  use.  It  is  essential 
to  the  economical  working  of  these  engines  that  the  cut-off 
mechanism  be  in  good  order  and  properly  adjusted.  Whenever 
the  valves  need  resetting,  the  final  adjustment  should  be  made 


HANDBOOK    ON    ENGINEERING.  195 

with  a  load  on  the  engine  and  with  the  indicator  attached  to  the 
cylinder,  the  valves  being  set  by  the  card  rather  than  by  the  eye. 
No  general  rule  can  be  given  for  setting  the  valves,  as  the  prac- 
tice varies  with  the  size  and  speed  of  the  engine  ;  nor  is  any  rule 
needed,  for  the  indicator  will  furnish  all  the  data  required.  The 
adjustments  may  then  be  made  so  as  to  secure  prompt  admission, 
sharp  cut-off,  prompt  release,  and  the  proper  compression. 

TO  FIND  THE  DEAD  CENTERS. 

When  setting  the  valve  of  an  engine  by  measuring  the  lead,  as 
is  the  usual  method,  it  is  necessary  that  the  crank  be  accurately 
placed  on  the  dead  centers  at  each  end  of  the  stroke.  Sometimes 
an  engineer,  when  adjusting  the  valves  of  his  engine,  will  attempt 
to  place  the  crank  on  the  dead  center  by  watching  for  the  point 
at  which  the  travel  of  the  cross-head  stops,  or  by  the  appearance 
of  the  connecting-rod  as  related  to  the  crank.  These  methods  are 
totally  unreliable  for  obtaining  accurate  results,  especially  the 
first  one  mentioned.  The  travel  of  the  cross-head  and  the  piston 
near  the  point  of  reversal  of  motion  is  very  slow  when  compared 
with  the  valve.  The  velocity  of  travel  of  the  valve  is  at  nearly 
its  maximum  amount  when  the  crank  is  on  the  dead  center,  and  a 
slight  error  in  finding  the  dead  center  point  makes  a  very  appre- 
ciable error  in  the  position  of  the  valve,  with  a  subsequent  error 
in  its  proper  setting. 

There  are  several  methods  for  finding  the  dead  center.  The 
method  that  can  be  recommended  and  the  one  that  should  always 
be  used  when  the  dead  center  of  an  engine  is  to  be  fonnd  is  that 
familiarly  known  as  "  tramming."  The  dead  centers  when  found 
by  this  method,  are  geometrically  accurate,  no  matter  if  the  engine 
is  out  of  level  or  if  the  shaft  is  above  or  below  the  axis  of  the 
cylinder.  Some  simple  tools  are  required  which  are  generally 
available,  with  the  exception  of  the  trams,  which  may  be  readily 


196 


HANDBOOK    ON    ENGINEERING. 


made  for  the  purpose.  Two  trams  are  required,  one  of  which 
should  be  6"  or  7"  long  and  the  other  about  24"  or  30",  as  the 
condition  may  require.  The  smaller  tram  may  be  made  of  i 
steel  wire  with  the  points  turned  over  at  right  angles  to  the  body, 
so  as  to  project  about  1".  The  points  should  be  sharpened  so 
that  a  hair  line  may  be  drawn  by  them.  The  larger  tram  should 
be  made  from  rod  of  at  least  f "  diameter  and  the  points  made  in 
the  same  way  as  for  the  smaller  tram.  Oftentimes,  the  long  tram 


Fig.  130.    Finding  the  dead  center. 

is  made  with  one  leg  longer  than  the  other,  on  account  of  being 
handier  to  reach  some  stationary  part,  but  this  is  a  minor  point, 
which  has  nothing  to  do  with  the  principle  to  be  described.  The 
other  tools  required  are  a  light  hammer,  a  prick-punch  a  pair  of 
10"  or  12"  wing  dividers  and  a  hermaphrodite  caliper,  or  a  scrib- 
ing block.  A  piece  of  chalk  will  also  be  found  convenient  to 
facilitate  scribing  lines  on  the  metal  parts  with  the  trams  or 
dividers.  Fig.  130  shows  the  use  of  the  trams. 

Having  the  necessary  tools,  we  are  ready  to  begin  operations, — 
and  may  start  at  either  end  of  the  stroke,  as  circumstances  may 
favor.  The  fly-wheel  is  turned  so  that  the  crank  stands  at 
about  the  angle  shown  in  the  accompanying  illustration,  which 


HANDBOOK    ON    ENGINEERING.  197 

may,  however,  be  approximated  as  the  operator  may  desire.  The 
effort  made,  being  to  give  sweep  enough  to  the  cross-head  to 
allow  accurate  measurements  and  still  not  have  such  an  excessive 
arc  on  the  fly-wheel  as  to  make  its  bisection  difficult. 

A  prick  mark  is  made  on  the  guides,  or  some  convenient  sta- 
tionary point,  as  at  .B,  and  an  arc  struck  on  the  cross-head  with 
the  small  tram.  At  the  same  time,  an  arc  is  scribed  on  the  rim 
of  the  fly-wheel  at  6r,  using  some  convenient  point  for  the  lower 
point  of  the  tram  as  at  7T,  The  fly-wheel  is  now  turned  until 
the  crank  passes  the  center  and  the  cross-head  travels  back  until 
the  scribed  line  will  coincide  exactly  with  the  point  of  the  tram 
when  held  in  the  same  position  as  in  the  first  case.  When  this 
point  has  been  reached,  the  wheel  is  stopped  and  a  second  arc  is 
scribed  on  the  fly-wheel  rim  at  F  with  the  tram  J.  The  herma- 
phrodite caliper,  or  the  scribing  block,  is  now  used  to  scribe  a 
concentric  line  D  E  on  the  fly-wheel  rim  and  the  arc  C  F  is 
bisected  with  the  dividers.  When  the  center  H  has  been  accu- 
ately  located,  it  should  be  carefully  prick-marked.  The  scribing 
of  the  concentric  line  D  E  is  a  refinement  that  is  not  strictly 
necessary  if  care  be  taken  to  locate  the  points  of  the  dividers  at 
the  same  distance  from  the  outer  periphery  of  the  wheel  in  each 
instance  when  finding  the  center  H.  The  marks  left  by  the  lathe 
tool  will  sometimes  be  plain  enough  for  a  guide.  When  the  center 
H  has  been  found,  the  fly-wheel  is  turned  so  that  the  point  of  the 
tram  will  fall  into  the  prick-mark  H  when  its  lower  end  is  in  the 
stationary  point  K.  When  this  condition  is  effected,  the  crank 
is  exactly  on  the  dead  center  and  the  position  of  the  valve  may 
be  taken  with  confidence  that  its  location  at  the  dead  center  point 
is  accurately  found.  The  same  procedure  is  followed  to  place  the 
crank  on  the  dead  center  at  the  opposite  end  of  the  stroke. 

The  cut  on  page  198  is  an  elevation  of  Tandem  Compound 
Engine,  showing  engine  erected  on  brick  foundation.  It  also 
shows  a  line  through  cylinders ;  also  a  line  over  the  shaft. 


198 


HANDBOOK    ON   ENGINEERING. 


HANDBOOK  ON  ENGINEERING.  199 

These  lines  are  used  in  the  erection  of  a  new  engine,  or  to  line 
up  an  old  one,  or  with  an  engine  that  is  out  of  line.  The  cut  also 
shows  how  the  foundation  is  made ;  also  how  the  anchor  bolt 
is  fastened. 

The  cut  on  page  200  shows  how  to  pipe  a  Twin  Tandem 
Compound  Condensing  Engine.  The  plan  shows  two  receivers, 
iieaters,  relief  valves,  gate  valves,  etc.,  and  is  so  arranged 
that  either  side  can  be  run  independently  of  the  other.  It 
also  shows  how  to  line  a  pair  of  these  engines  by  following 
the  lines  and  noting  the  distance  between  each  line.  An  engineer 
would  have  no  trouble  in  lining  up  a  pair  of  these  engines. 

HOW  TO  LINE  AN  ENGINE. 

The  method  followed  when  lining  different  types  of  engines, 
such  as  vertical,  horizontal,  portable  etc.  is  as  follows: — 

The  method  followed  in  lining  any  piston  engine  is  essentially 
the  same  in  all  cases,  as  far  as  determining  when  adjustments  are 
needed.  The  method  of  making  the  adjustments  after  the  char- 
acter and  amount  of  them  is  determined,  depends  entirely  on  the 
construction  of  the  engine,  and  will  necessarily  have  to  be  deter- 
mined in  each  individual  case,  Lining  an  engine  consists  of  ad- 
justing the  guides  so  they  shall  be  parallel  to  the  bore  of  the 
cylinder,  and  in  such  a  position  that  the  center  of  the  piston 
socket  of  the  cross-head  shall  coincide  with  the  axis  of  the  cylin- 
der. Under  these  conditions  only,  can  the  piston  and  cross-head 
travel  through  the  stroke  freely,  and  without  distorting  any  of  the 
parts.  After  this  adjustment  has  been  made,  the  truth  of  the 
right-angle  position  of  the  shaft  must  be  determined  as  being 
"out  of  square;"  this  will  make  an  engine  run  badly,  and  is 
often  the  unsuspected  cause  of  much  trouble  to  engineers.  We 
will  assume  that  we  have  an  engine  with  four-bar  or  locomotive 
guides,  and  that  the  connecting  rod,  cross-head,  back  cylinder 


200 


HANDBOOK   ON   ENGINEERING. 


HANDBOOK    ON  ENGINEERING. 


201 


head  and  piston  have  been  removed.  If  the  engine  is  of  the 
horizontal  type  the  first  step  will  properly  be  to  ascertain  if  the 
engine  is  level  on  the  foundation,  and  if  not,  proceed  to  make  it 
so.  After  having  leveled  the  engine,  stretch  a  smooth  linen 
line,  as  shown  in  Fig.  133,  through  the  bore  of  the  cylinder  and 
the  stuffing-box,  to  a  point  beyond  the  shaft,  where  it  should  be 
attached  to  an  iron  rod  driven  into  the  floor.  The  other  end  is 
fastened  to  a  cross-bar  bolted  across  the  face  of  the  cylinder  to 


Fig.  183.    Lining  up  an  engine. 

two  of  the  studs,  as  shown  in  Fig.  133,  or  the  bar  may  preferably 
be  somewhat  longer  than  one-half  of  the  diameter  of  the  cylinder, 
and  with  a  saw  cut  for  a  short  distance  lengthwise  at  the  inner 
end.  In  this  case,  it  is  held  by  only  one  of  the  cylinder  studs 
and  can  be  somewhat  more  easily  adjusted.  The  line  or  cord  is 
adjusted  to  approximately  the  proper  position,  and  is  drawn  taut 
and  fastened  through  the  cross-bar  by  being  tied  to  a  short  stick 
that  is  too  long  to  pass  through  the  hole.  In  this  position  it  is 
held  by  the  friction,  and  can  be  readily  adjusted  to  the  required 
position.  An  assistant  is  required  to  move  the  line  in  the  direc- 
tions indicated,  as  the  work  proceeds,  and  then  we  are  ready  to 
center  it  in  the  cylinder.  The  only  tool  required  for  this  purpose 
is  a  light  pine  stick  of  slightly  less  length  than  the  radius  of  the 


202  HANDBOOK    ON    ENGINEERING. 

bore,  and  it  should  have  an  ordinary  pin  pushed  into  the  head  for 
a  ' 'feeler."  Now  adjust  the  line  in  the  cylinder  so  that  the  head 
of  the  pin  will  just  tick  the  line  from  four  points  of  the  counter- 
bore,  which  is  always  the  part  of  the  cylinder  to  work  from,  as  it 
is  not  affected  by  the  wear.  The  line  should  then  be  adjusted 
to  the  center  of  the  other  end  of  the  cylinder,  but  not  from  the 
stuffing-box,  as  this  is  likely  to  be  out  of  center  somewhat. 
Make  the  adjustment  at  this  end  from  the  counterbore,  if  pos- 
sible, the  same  as  in  the  first  instance,  and  then  it  will  be  neces- 
sary to  try  the  position  of  the  line  in  the  back  end  of  the  cylinder 
as  the  changes  made  at  the  other  end  will  affect  it  slightly.  After 
the  line  is  truly  centered,  we  are  ready  to  adjust  the  guides. 
With  some  types  of  cross-heads,  it  is  possible  to  use  the  cross- 
head  for  determining  the  proper  location  of  the  guides,  but  with 
the  ordinary  form, such  as  shown  in  Fig.  133,  this  cannot  be  done 
but  we  will  need  a  tool  similar  to  that  shown  in  sketch,  which 
consists  simply  of  a  piece  of  flat  iron  long  enough  to  reach  across 
the  guides,  and  having  a  hole  drilled  and  tapped  in  the  center  for 
the  thumb-screw.  This  thumb-screw  is  adjusted  so  that  its  point 
is  the  same  distance  from  the  lower  side  of  the  bar,  as  the  lower 
face  of  the  wings  of  the  cross-head  are  from  the  center  of  the 
piston  socket.  To  find  this  distance,  lay  a  straight  edge  across 
the  end  of  the  cross-head  and  draw  the  line  A  B,  and  then,  hav- 
ing found  the  center  of  the  hole,  the  measurement  may  be  accur- 
ately taken.  The  lower  guides  are  now  adjusted  by  the  tool,  so 
that  the  point  of  the  screw  will  tick  the  line  throughout  the 
length,  and  then  the  top  guides  are  put  in  position  with  the  cross- 
head  in  place  and  adjusted  for  a  proper  working  fit. 

Before  removing  the  line  from  the  cylinder,  however,  the  shaft 
should  be  tested  for  the  truth  of  its  right-angle  position,  which 
may  be  done  by  calipering  between  the  crank  disc  and  the  line  at 
the  points  H  and  J.  If  the  distances  are  equal,  the  shaft  is 
square  with  the  bore  of  the  cylinder,  providing,  of  course,  that 


HANDBOOK   ON   ENGINEERING.  203 

the  disc  is  faced  true  with  the  shaft.  If  there  is  any  doubt  as  to 
its  accuracy,  turn  the  shaft  as  nearly  half  way  around  as  the 
crank-pin  will  admit  without  disturbing  the  line.  Then  caliper 
the  distance  of  a  point  on  the  disc  that  will  not  be  far  removed 
from  the  first  position,  thus  reducing  the  chance  for  error.  If 
the  shaft  shows  4  '  out  '  '  move  the  outward  bearing  until  the  meas- 
urements show  equal  in  both  positions.  The  horizontal  truth  of 
the  shaft  can  be  found  by  laying  a  level  on  it  and  if  "  out," 
raise  or  lower  the  out-board  bearing  until  the  level  shows  fair. 
Work  of  this  kind  requires  skill  and  patience  and  belongs  prop- 
erly to  the  sphere  of  the  chief  engineer.  It  requires  a  delicacy  of 
touch  and  an  appreciation  of  what  is  meant  by  close  measurement 
that  can  come  only  through  experience.  In  centering  the  line, 
one  should  be  able  to  detect  when  it  is  as  little  as  T^TF  of  an  inch 
out  of  center.  A  piece  of  ordinary  tissue  paper  is  about  .00125 
inch  thick.  A  man  should  be  able,  therefore,  to  adjust  a  line  so 
accurately  that  if  the  "  feeler,"  with  one  or  more  pieces  of  the 
paper  under  it,  just  clips  the  line,  it  will  miss  the  line  when  one 
thickness  is  removed.  While  it  may  not  always  be  necessary  to 
work  as  closely  as  this,  a  person  cannot  expect  to  line  up  engines 
successfully  until  he  has  a  full  knowledge  of  what  this  degree  of 
accuracy  means. 

Engine  Formulas. 

Diam.  cyl.  for  given  H.P.  =  -,/  __  33000  XH.P.        ^ 

v  Piston  speed  XM.E.P.  ' 


Stroke  in  feet  =  P^ton  speed  in  feet  per  min. 

Revs.  X  2 

Piston  speed  in  feet  per  min. 
Keys,  per  min.  =  Length  of  stroke  in  feet  X  2 

83000  XH.P.  _ 
Piston  speed  =  Areft  Qf  p.gton  in  gq  inches  x  M  E  p> 

33000  XH.P. 
Area  of  piston  in  sq.  ins.  =  M.E.P.X  piston  speed 

33000  X  H.  P. 
M.E.P.  required  =  Area  of  ristOnX  Piston  speed 


204 


HANDBOOK    ON    ENGINEERING. 


HANDBOOK    ON    ENGINEERING.  205 


CHAPTER   XIa. 

DIRECTIONS  FOR   SETTING   UP    ADJUSTING   AND    RUNNING 
THE  CORLISS  STEAM  ENGINE. 

Location  of  foundation* — The  foundation  must  be  at  right 
angles  with  main  line  shaft.  If  main  line  shaft  is  not  already  in 
position,  then  foundation  must  be  set  by  two  points,  located  and 
connected  with  a  line  parallel  with  the  buildings,  and  at  right 
angles  to  an  imaginary  line  through  center  of  cylinder. 

Foundation  plans  should  show  all  center  lines.  If  a  templet 
is  furnished  to  locate  the  foundation  accurately  for  the  mason,  the 
center  line  of  engine  cylinder  and  guides  and  right  angle  for 
crank  center  are  drawn  thereon. 

Cap  Stones*  —  Examine  carefully  the  lap  faces  of  cap  stpnes 
and,  if  necessary,  have  them  trimmed  off  by  cutter  or  mason,  so 
that  each  is  true  and  level,  and  in  exactly  the  plane  shown  in 
foundation  plan. 

Cylinders  and  frame*  —  Put  engine  cylinder  and  frame  in 
position  and  bolt  them  together. 

Lining;  off  crank  shaft  and  out-end  bearing.  —  Stretch  a 
line  at  right  angles  to  main  center  line,  through  main  bearing  to 
represent  center  line  of  crank  shaft.  See  that  this  line  is  exactly 
in  the  center  and  level.  By  this  line  place  out-end  bearing  square 
and  true.  Put  crank  shaft  in  its  bearings  after  bottom  box  has 
been  placed  in  main  bearings.  Insert  quarter  boxes  and  adjust- 
ing wedges  into  main  bearing  and  put  cap  on. 

To  ascertain  that  shaft  is  at  exact  right  angles  to  main  center 
line,  turn  engine  shaft  until  the  crank  pin  comes  nearly  to  the 


206  HANDBOOK   ON   ENGINEERING. 

main  center  line,  then  with  a  pair  of  calipers,  or  rule,  measure  from 
shoulder  of  crank-pin  to  line,  and  after  noting  this  distance,  turn 
the  crank  back  towards  opposite  center  until  pin  is  in  same 
relative  position  to  line,  and  measure  again.  If  both  measurements 
do  not  correspond,  out-end  bearing  must  be  moved  either  way  as 
required,  until  measurements  show  equal.  Then  take  up  slack 
around  shaft  in  main  bearing,  being  careful  not  to  force  the 
adjusting  wedge  too  tight. 

Fly-wheels*  —  The  fly-wheel  is  next  placed  on  shaft  and  firmly 
keyed  in  position. 

Placing1  valve  gear*  —  Steam  and  exhaust  valve  covers  or  bon- 
nets on  valve  gear  side  are  next  bolted  to  place,  taking  care  that 
no  dirt  or  foreign  substance  gets  between  the  surface  underneath 
the  covers. 

Valve  stems  are  inserted  from  opposite  or  front  of  cylinder  and 
the  valves  put  in  after  them,  the  T  head  of  valve  stem  entering 
slot  in  valve.  Couple  up  all  valve  gear  parts,  i.  e.,  disc  plate 
valve-steam  cranks,  valve-connecting  rods,  dash-pots  and  dash-pot 
rods,  vajye-rod  rocker,  eccentric  and  straps  on  crank-shaft,  first 
and  second  eccentric  rods.  The  dash-pots  should  be  thoroughly 
cleaned  and  oiled  before  putting  in  place. 

ADJUSTMENT  OF  CORLISS  VALVE  GEAR  WITH  SINGLE  AND 
DOUBLE  ECCENTRICS. 

A  brief  description  of  the  essential  parts  of  the  Corliss  engine 
valve  gear  will  assist  in  obtaining  a  clear  conception  of  the 
subject. 

When  a  single  eccentric  drives  both  steam  and  exhaust  valves 
the  range  of  cut-off  is  limited  to  about  half  the  piston  stroke. 
This  Tvill  become  obvious  by  considering  the  following  necessary 
conditions ;  — 


HANDBOOK    OF   ENGINEERING 


207 


After  the  eccentric  has  reached  the  extreme  of  its  throw  as 
shown  in  Fig.  135  in  either  direction  all  valve  gear  motions  are 
reversed. 


Fig.  135.    Showing  eccentric  in  extreme  position. 

The  steam  valve  must  be  released  before  the  eccentric  motion 
is  reversed,  for  if  the  hook  does  not  strike  the  knock-off  cam 
during  its  forward  motion,  it  cannot  strike  it  during  its  return 
motion. 

The  maximum  exhaust  opening,  or  the  middle  of  the  exhaust 
period,  must  occur  when  the  eccentric  is  at  the  extreme  of  its 
throw  as  in  Fig.  135. 

Now,  in  order  to  release  the  expanded  steam  in  the  cylinder 
before  the  commencement  of  the  return  stroke  and  to  secure  the 
exhaust  closure  a  little  before  the  end  of  the  return  stroke,  the 
middle  of  the  exhaust  period  or  the  extreme  of  the  eccentric 
throw  must  evidently  occur  before  the  middle  of  the  return 
stroke,  and,  therefore,  the  extreme  throw  of  the  eccentric  in  the 
opposite  direction  must  occur  before  the  middle  of  the  forward 
stroke,  and  the  valve  must  be  released  before  this  point  is  reached 
if  released  at  all. 

It  will  be  understood  from  the  foregoing  that  late  release  and 
late  exhaust  closures  are  conditions  imposed  by  the  single 
eccentric  valve  gear,  and  these  conditions  agree  very  well  with 
moderate  rotative  speed  ;  but  at  higher  speed  earlier  release  and 


208  HANDBOOK    ON    ENGINEERING. 

more  compression  may  be  required.  This  may  be  effected  by 
moving  the  eccentric  forward  on  the  shaft,  but  the  reversing  of 
the  steam  valve  motion  would  then  occur  at  an  earlier  stage  of 
the  forward  stroke  and  the  range  of  cut-off  would  be  correspond- 
ingly shortened.  Earlier  exhaust  closure  could  be  had  by  giving 
the  exhaust  valve  more  lap,  but  this  would  involve  a  later  release 
of  the  expanded  steam  at  the  end  of  the  stroke.  On  the  other 
hand,  shortening  the  exhaust  lap  would  give  earlier  release  but 
insufficient  or  no  compression. 

In  Figs*  136  and  137  similar  capital  letters  of  reference  indicate 
the  same  parts  of  the  mechanism. 

Fig.  136  shows  all  the  essential  parts  of  the  valve  gear.  The 
steam  valves  work  in  the  chambers  S  8  and  the  exhaust  valves 
work  in  the  chambers  E  E.  The  double-armed  levers  D  D 
work  loosely  on  the  hubs  of  the  steam  bonnets ;  they  are  con- 
nected to  the  wrist-plate  B  by  thr  rods  K  K,  the  levers  M  M  are 
keyed  to  the  valve  stems  J  J,  and  are  also  connected  by  the  rods 
0  0  to  the  dash-pots  P  P.  The  double-armed  levers  D  carry  at 
their  outer  ends  what  are  called  steam  hooks  FF,  these  being  pro- 
vided with  hardened  steel  catch  plates,  which  engage  with  arms 
M  M,  making  the  arm  M  and  the  hook  F  work  in  unison  until 
steam  is  to  be  cut  off.  At  this  point  another  set  of  levers  or  cams 
G  6r,  which  are  connected  by  the  cam  rods  II H,  to  the  governor? 
come  into  play,  causing  the  catch  plates  on  the  hooks  F  to  release 
the  arms  M  M,  the  outer  ends  of  which  are  then  pulled  downwards 
by  the  dash-pot  plunger,  causing  the  steam  valves  to  rotate  on 
their  axis  and  thus  cut  off  steam.  These  are  the  essential  fea- 
tures of  the  Corliss  gear. 

The  exhaust  valve  arms  N  are  connected  to  the  wrist-plate  by 
the  rods  L  Z/,  and  it  is  seen  that  all  the  valves  receive  their 
motion  from  the  wrist- plate  B;  the  latter  receives  its  motion 
from  the  hook-rod  A;  this  rod  is  generally  attached  to 
a  rocker  arm  not  shown;  to  this  arm  the  eccentric  rod  is 


HANDBOOK   ON   ENGINEERING. 


210 


HANDBOOK    ON    ENGINEERING, 


also  attached.  The  rocker  arm  is  usually  placed  about  mid- 
way between  the  wrist-plate  and  eccentric,  and  in  the  center 
of  its  travel  stands  in  a  vertical  position. 

The  setting  of  the  valves  is  not  a  difficult  matter,  when,  on 
the  wrist-plate,  its  support,  valves  and  cylinder,  the  customary 
marks  have  been  placed  for  finding  the  relative  positions  of 
wrist-plate  and  valves. 


0  c 


•-  H 

>t 


' 


Q- 


f*l-               t  Af 

j^  ft. ^ 


Fig.  187.    Diagram  of  Corliss  gear  and  valves. 

Now,  referring  to  Fig.  137,  when  the  back  bonnets  of  the  valve 
chambers  have  been  taken  off,  there  will  generally  be  found  a  mark 
or  line,  r,  on  the  end  of  each  steam  valve  s  s,  coinciding  with  the 
working  or  opening  edge  of  each  valve  ;  another  line,  £,  will  be 
found  on  each  face  of  the  steam  valve  chamber  coinciding  with 
the  working  edge  of  the  steam  port.  The  exhaust  valves  and 
their  chambers  are  marked  in  a  similar  way,  i.  e.,  the  line  u  on 
the  end  of  each  exhaust  valve  coincides  with  the  working  edge  of 
the  valve,  and  the  line  #,  on  the  face  of  ^ach  exhaust  valve 


HANDBOOK   ON   ENGINEERING.  211 

chamber,  coincides  with  the  working  edge  of  the  exhaust  port. 
On  the  hub  of  the  wrist-plate  will  be  found  three  lines  n,  c,  w, 
placed  in  such  a  way  that  when  the  line  c  coincides  with  the 
line  b  on  wrist -plate,  the  wrist  plate  will  stand  exactly  in  the 
center  of  its  motion,  and  when  the  line  b  coincides  with  either 
of  the  lines  TI,  ft,  the  wrist -plate  will  be  at  one  of  the  extreme 
ends  v  or  w  of  its  travel. 

In  setting  the  valves,  the  first  step  will  be  to  set  the  wrist- 
plate  in  its  central  position,  so  that  the  lines  b  and  c  will  coin- 
cide, and  fasten  the  wrist-plate  in  this  position  by  placing  a 
piece  of  paper  between  it  and  the  washer  R  on  its  supporting 
pin.  Now  set  the  steam  valves  so  that  they  will  have  a  slight 
amount  of  lap,  that  is  to  say,  the  lines  r,  r,  must  have  moved  a 
little  beyond  the  lines  £,  t.  The  amount  of  this  lap  depends 
much  on  individual  preference  and  experience ;  it  ranges  from 
^  to  J  for  small  engines,  and  from  J  to  |  inch  for  compara- 
tively large  engines.  This  lap  is  obtained  by  lengthening  or 
shortening  the  rods  K K\>y  means  of  the  adjusting  nuts. 

Now  place  the  exhaust  valves  e,  e,  by  lengthening  or  shorten- 
ing the  rods  L  L  by  means  of  the  adjusting  nuts,  in  a  position 
so  that  the  working  edges  will  just  open  the  exhaust  ports,  or, 
in  other  words,  place  the  lines  u  and  x  in  line  with  each  other 
as  indicated  in  illustration. 

The  next  step  will  be  to  adjust  the  rocker  arm.  .  Set  this  arm 
in  a  vertical  position  by  means  of  a  plumb  line,  and  connect  the 
eccentric  rod  to  it ;  then  turn  the  eccentric  around  on  the  shaft, 
and  see  that  the  extreme  points  of  travel  are  at  equal  distances 
from  the  plumb  line.  To  secure  this  a  little  adjustment  in  the 
stub  end  of  the  eccentric  rod  may  be  necessary.  Now  connect  the 
hook  rod  A  to  the  wrist-plate.  The  paper  between  the  wrist- 
plate  and  the  washer  on  the  supporting  pin  should  now  be  taken 
out,  so  that  the  wrist-plate,which  is  connected  to  the  valves, can 
be  swung  on  its  pin.  Now  turn  the  eccentric  around  on  the  shaft 


212  HANDBOOK    ON    ENGINEERING. 

in  order  to  determine  the  extreme  points  of  travel  of  the  wrist- 
plate.  If  all  parts  have  been  correctly  adjusted,  the  line  b  will 
coincide  with  the  lines  w-,  n,  at  the  extreme  points  of  travel ;  if 
this  is  not  the  case,  the  hook  rod  will  have  to  be  adjusted  at  its 
stub  end  so  as  to  obtain  the  desired  equalized  motion  of  the 
wrist-plate. 

The  next  step  will  be  to  set  the  valves  correctly  with  reference 
to  the  position  of  the  crank ;  to  do  this  the  length  of  the  rods  K, 
K,  L,  and  L  must  not  be  changed,  but  the  following  mode  of 
procedure  should  be  followed :  Place  the  crank  on  one  of  its  dead 
centers  (see  page  195)  and  turn  the  eccentric  loosely  on  the  shaft 
in  the  direction  in  which  the  engine  is  to  run,  until  the  steam 
valve  nearest  to  the  piston  shows  an  opening  or  lead  of  -J^-  to  -fa 
inch.  After  the  proper  lead  has  been  given  to  this  valve,  secure 
the  eccentric,  and  turn  the  shaft  with  eccentric  in  the  same  direc- 
tion in  which  the  engine  is  to  run  until  the  crank  is  on  the  oppo- 
site dead  center,  and  notice  if  the  opening  or  lead  at  this  end  of 
the  cylinder  is  the  same  as  on  the  other  steam  valve ;  if  not, 
shorten  or  lengthen  slightly,  as  may  appear  necessary,  the  con- 
nection between  the  wrist-plate  and  eccentric.  Of  course  much 
adjustment  in  the  length  of  these  connections  is  not  admissible 
without  resetting  the  valves  with  reference  to  the  wrist-plate.  The 
compression  on  an  engine  is  a  very  important  factor,  upon  which 
cool  and  quiet  running  depends.  With  exhaust  valves  line  and 
line  about  5  per  cent  compression  is  secured,  which  is  equal  to  If 
for  36"  stroke  and  2"  for  42"  stroke.  In  case  more  compression 
is  desired,  the  exhaust  valves  must  be  given  a  little  lap. 

To  set  the  exhaust  valves  for  a  given  compression,  say,  2 
inches,  first  measure  off  2  inches  from  the  ends  of  the  cross- head 
travel  as  shown  in  Fig.  138  (not  from  the  ends  of  the  guide). 
Then  turn  the  crank  in  the  direction  it  is  to  run  until  the  end  of 
the  crosshead  reaches  the  line  on  the  guide.  Adjust  the  exhaust 
valve  corresponding  to  this  end  of  the  stroke  so  that  it  just  closes 


HANDBOOK    ON   ENGINEERING. 


213 


the  port.  Turn  the  crank  over  the  center  and  back  on  the  return 
stroke  until  the  opposite  end  of  the  cross-head  reaches  the  line  on 
the  opposite  end  (to  the  first  mark)  of  the  guide.  Then  adjust 
the  exhaust  valve  corresponding  to  this  end  of  the  stroke  so  that 
it  just  closes  the  port.  Both  exhaust  valves  will  then  close  the 
ports  when  the  piston  reaches  a  point  2  inches  from  the  working 
end  of  the  guide  and  the  engine  will  then  have  exactly  2  inches 


Fig.  138.    Laying  out  compression  marks  on  guide. 

compression.  If  this  is  found  to  be  too  much  or  too  little,  as 
determined  by  the  running  qualities  of  the  engine,  it  may  be 
varied  either  way  by  adjusting  the  length  of  the  rods  L  and  L, 
being  careful  to  turn  each  nut  exactly  the  same  amount. 

The  only  thing  which  remains  now  to  be  done  is  to  adjust  the 
cam  rods  H,  H,  to  produce  an  equal  cut-off  at  each  end  of  the 
cylinder.  On  the  column  of  most  Corliss  engine  governors  will 
be  found  a  stop  device,  sometimes  in  the  form  of  a  loose  pin, 
some  form  of  cam  motion  or  movable  collar.  This  device  is  for 
the  purpose  of  preventing  the  governor  from  reaching  its  lowest 
position,  for  when  it  reaches  the  latter  position  the  valves  should 
not  hook  on.  Should  the  governor  belt  break  or  become  ineffect- 


214  HANDBOOK   ON    ENGINEERING. 

ive,  the  governor  will  stop  and  reach  its  lowest  position  on  the 
column,  thereby  bringing  the  safety  cam  Y  in  underneath  the 
inner  member  of  the  hook  F  which  prevents  the  latter  from 
engaging  arm  Jf,  and  as  the  valves  cannot  hook  on  when  it  is  in 
this  position  the  admission  of  steam  to  the  cylinder  is  entirely 
shut  off  and  the  engine  will  come  to  a  standstill. 

It  will  be  apparent  that  the  stop  on  the  governor  column  should 
be  removed  or  otherwise  rendered  inoperative  as  soon  as  the 
engine  has  attained  full  speed,  and  should  again  be  placed  in 
active  position  when  stopping  the  engine  in  the  usual  way.  As 
the  stop  just  mentioned  determines  the  lowest  position  of  the 
governor  at  which  the  valves  should  hook  up,  it  should  be  kept 
in  place  while  the  foregoing  adjustments  are  being  made. 

Next,  unhook  the  reach  rod  from  the  wrist-plate  and  by  means 
of  the  starting  bar  move  the  wrist-plate  over  until  the  lines  b  and 
n  are  nearly  opposite  each  other.  The  head  end  valve  should 
now  have  opened  the  port  to  nearly  the  limit,  which  may  be 
ascertained  by  the  marks  on  the  ends  of  the  valve.  Now,  adjust 
the  governor  rod  H  so  that  the  projection  or  cam  on  the  disk  G 
operated  by  the  governor  will  come  in  contact  with  the  inner 
member  of  the  steam  hook  F,  so  that  the  valve  will  be  tripped  or 
released  when  the  marks  b  and  n  are  exactly  in  line.  As  all 
governors  do  not  move  an  equal  amount  to  produce  a  given 
change  in  the  point  of  cut-off,  it  will  be  safer  to  hook  the  reach 
rod  on  the  wrist-plate  and  have  the  engine  turned  in  the  direction 
in  which  it  is  to  run,  until  the  head  end  valve  is  released,  than  to 
adjust  the  cut-off  with  the  use  of  the  starting  bar  only.  To 
prove  the  correctness  of  the  cut-off  adjustment,  raise  the  gover- 
nor balls  to  a  position  where  they  probably  would  be  when  at 
work  and  block  them  there ;  then,  with  the  connections  made 
between  the  eccentric  and  the  wrist-plate,  turn  the  engine  shaft 
slowly  in  the  direction  in  which  it  is  to  run,  and  when  the 
valve  is  released,  measure  upon  the  slide  the  distance  which 


HANDBOOK   ON   ENGINEERING. 


215 


the  crosshead  has  moved  from  its  extreme  position.  Continue  to 
turn  the  shaft  in  the  same  direction,  and,  when  the  other  valve  is 
released,  measure  the  distance  through  which  the  crosshead  has 
moved  from  its  extreme  position,  and  if  the  cut-off  is  equalized, 
these  two  distances  will  be  equal  to  each  other.  If  they  are  not, 
adjust  the  length  of  the  cam  rods  until  the  points  of  cut-off  are 
equal  distances  from  the  beginning  of  the  stroke.  Replace  the 
back  bonnets  and  see  that  all  connections  have  been  properly 
made,  which  will  complete  the  setting  of  the  valves. 


Fig.  139.    Diagram  of  doable  eccentric  gear. 


ADJUSTMENT  WITH  TWO  ECCENTRICS. 

In  order  to  obtain  a  greater  range  of  cut-off  in  Corliss  engines 
a  separate  steam  and  exhaust  eccentric  is  used.  With  two  eccen- 
trics the  admission  and  exhaust  valves  can  be  adjusted  independ- 
ently, and  steam  may  be  cut  off  anywhere,  nearly  to  the  end  of 
the  stroke. 

The  work  of  setting  the  valves  of  a  Corliss  engine  having  two 


216 


HANDBOOK   ON   ENGINEERING. 


HANDBOOK   ON   ENGINEERING.  217 

eccentrics  is  not  particularly  complicated  as  many  engineers  seem 
to  think.  After  inspecting  the  type  of  releasing  gear  employed 
and  knowing  in  which  direction  the  engine  is  to  run,  finding  the 
direction  in  which  to  turn  the  eccentric  becomes  a  very  simple 
matter.  When  setting  the  steam  valves  we  have  one  eccentric  to 
turn  as  in  the  case  of  the  single  eccentric  engine,  and  when  set- 
ting the  exhaust  valves  another  eccentric  must  be  turned,  but  this 
does  not  add  complication  to  the  work,  although  it  requires  a 
little  more  time.  The  work  of  centralizing  the  positions  of  the 
various  parts,  equalizing  the  movements  and  setting  and  adjust- 
ing the  valve  gear  is  practically  the  same  as  with  the  single  eccen- 
tric engine.  Set  the  wrist-plate  central  as  shown  in  Fig.  139,  and 
adjust  the  valve  rods ;  but  in  this  case  the  steam  valves  are  set 
with  negative  lap,  which  is  usually  a  little  less  than  half  the 
port  opening.  The  first  step  is  to  set  the  exhaust  eccentric 
(as  it  is  generally  placed  next  to  the  bearing).  To  do  this 
turn  the  engine  until  the  piston  is  in  the  position  shown 
in  Fig.  140,  so  as  to  obtain  a  compression  of  about  5 
per  cent  of  the  stroke.  Then  turn  the  exhaust  eccentric 
loosely  on  the  shaft  in  the  direction  the  engine  is  to  run,  until  the 
exhaust  valves  are  line  and  line.  Then  secure  the  eccentric  and 
turn  the  engine  on  the  other  end  in  the  same  position  to  prove 
the  correctness  of  the  other  exhaust  valve. 

The  next  step  is  to  set  the  steam  eccentric ;  place  the  crank 
on  either  one  of  its  dead  centers,  then  turn  the  steam  eccentric 
loosely  on  the  shaft  until  the  steam  valve  on  the  same  end  the 
piston  is,  has  the  required  opening  or  lead,  which  varies  from  -fa" 

to  Ty. 

These  directions  apply  to  engines  in  which  the  reach  rod  from 
the  eccentric  is  connected  to  the  wrist-plate  above  the  center 
pin  R,  Fig.  No.  136.  When  the  reach  rod  is  connected  to  wrist- 
plate  below  the  pin  jR,  the  eccentric  should  be  turned  the  opposite 
direction  to  that  in  which  the  engine  is  to  run. 


218 


HANDBOOK  ON  ENGINEERING. 


HANDBOOK    ON    ENGINEERING. 


219 


The  arrangement  of  the  steam  rods  in  Fig.  136  is  in  every  re- 
spect satisfactory  in  connection  with  a  single  eccentric  valve  gear, 
for  in  that  case  a  slow  initial  valve  motion  is  imperative,  and  it  is 
obtained  by  the  lateral  movement  of  the  radius  rod.  But  with 
two  eccentrics  quicker  initial  motion  is  feasible  and  desirable,  and 
it  is  obtained  by  reversing  the  valve  motion  as  in  Fig.  139.  Sepa- 
rate eccentrics  require  separate  wrist-plates,  which  are  usually 
placed  on  the  same  pin. 


Fig.  142.    Diagram  showing  steam  distribution. 

Figs*  141  and  142  show  how  the  eccentrics  may  be  placed  on  the 
shaft.  The  steam  eccentric  is  at  point  4,  Fig.  141,  the  exhaust 
eccentric  is  at  point  1,  Fig.  142,  and  the  crank  is  at  its  dead  center 
at  C.  Individual  eccentric  circles  are  shown  for  the  sake  of  clear- 
ness. An  imaginary  motion  of  the  eccentric  will  point  out  the 
various  events.  Referring  to  Fig.  141,  near  point  2,  at  the  end  of 


220 


HANDBOOK   ON   ENGINEERING. 


the  throw,  the  hook  connects  with  the  steam  valve ;  at  point  3 
the  steam  edges  are  at  the  point  of  separating  and  the  eccen- 
tric motion  2-3  determines  the  initial  valve  motion.  When  the 
eccentric  is  at  point  4  the  crank  is  at  its  dead  center  as 
shown.  At  point  5  the  steam  wrist-plate  is  in  its  central  position 
and  in  that  position  the  valve  does  not  cover  the  port,  as  with 
the  single  eccentric  gear,  but  the  port  is  open  to  a  certain  extent, 
determined  by  the  eccentric  motion  3-5.  Point  7  marks  the  end 


Fig.  148.    Diagram  showing  steam  distribution. 

of  the  throw,  and  the  corresponding  position  of  the  crank  is  at  C1 
at  about  three-quarters  of  the  piston  stroke,  and  the  limit  of  cut- 
off is  a  little  later.  If  the  hook  does  not  strike  the  knock- 
off  cam  the  valve  will  remain  open  until  closed  by  the  return 
stroke  of  the  eccentric  at  point  9,  near  the  middle  of  the 
return  piston  stroke.  The  exhaust  action  is  discernible,  Fig.  141. 


HANDBOOK   ON   ENGINEERING. 


221 


It  is  similar  to  the  single  eccentric  action,  but  with  this  differ- 
ence, that  the  release  at  point  5  occurs  at  about  95  per  cent  of 
the  stroke,  and  the  exhaust  is  also  cut  off  at  about  95  per  cent 
of  the  return  stroke  at  point  8. 

The  motion  of  the  exhaust  valve  after  it  has  closed  the  port  is 
determined  by  the  eccentric  motion  8-2-5,  and  full  period  of 
exhaust  opening  is  obtained  by  the  eccentric  motion  5-7-8.  In 
case  the  exhaust  valve  motion  is  designed  and  set  with  lap,  Fig. 
143  shows  the  effect  lap  has  on  the  exhaust  valves.  The  lap  when 
wrist-plate  is  central  is  determined  by  motion  A-B.  It  will  be 


Fig.  144.    Relative  position  of  valves  and  crank  pin. 

noticed  that  the  compression  begins  at  A  at  about  90  per  cent  of 
the  stroke,  and  the  release  at  E  occurs  at  98  per  cent  of  the 
return  stroke  and  the  exhaust  opening  E,  (7,  A,  is  shortened. 
Where  lap  is  used  on  the  exhaust  valve  it  has  the  effect  of  making 
earlier  compression  and  later  release.  A  valve  gear  designed  to 
be  operated  by  a  single  eccentric  cannot  very  well  be  made  to  cut 
off  much  later  than  at  half  stroke,  even  when  a  separate  exhaust 
eccentric  is  added.  For  the  slow  initial  valve  motion  requires  at 
least  half  the  throw  of  the  eccentric,  and  the  other  half  is  not 
sufficient  for  a  late  cut-off,  and  it  will  readily  be  seen  from  an  in- 
spection of  Figs.  137  and  139,  that  a  quicker  initial  valve  motion  in 


222  HANDBOOK    ON    ENGINEERING. 

. 

Fig.  137  would  involve  radical  changes  in  the  valve  gear.  However, 
the  range  of  cut-off  may  be  extended  by  moving  the  eccentric 
back,  sacrificing  the  lead,  and  to  this  there  is  no  objections  when 
it  does  not  involve  later  release.  The  advantage  gained  by  a 
second  eccentric  would  consist  in  more  compression  and  earlier 
release.  After  setting  the  valves  and  making  the  final  adjustment, 
if  it  is  convenient  an  indicator  should  be  applied  to  the  engine 
when  at  work  to  verify  the  adjustment  of  the  valves  for  the  best 
possible  conditions  for  economical  operation. 

Fig.  143  indicates  position  of  eccentric  at  f  cut-off,  which  can 
be  extended  some  by  giving  the  steam  valves  a  little  more  nega- 
tive lap,  but  as  this  shortens  the  amount  of  lap  when  closed,  it 
may  cause  leakage  in  the  steam  valves. 
' 

COMPOUND  ENGINE. 

The  compound  engine  is  practically  two  single  engines  con- 
nected together  and  so  arranged  that  the  exhaust  steam  from 
one  engine  passes  into  and  becomes  the  c '  live  "  steam  for  the 
other,  in  other  words  the  first,  or  high  pressure  cylinder  receives 
its  supply  of  steam  from  the  boiler  and  the  second  or  low 
pressure  cylinder  receives  its  supply  from  the  high  pressure 
cylinder.  The  object  of  the  compound  engine  is  to  enable  the 
steam  to  expand  to  the  lowest  possible  pressure  with  the  least 
loss  by  condensation.  When  steam  expands  its  temperature 
decreases,  so  that  by  the  time  the  piston  reaches  the  end  of  the 
stroke  the  temperature  of  the  steam  and  consequently  the  tem- 
perature of  the  cylinder  walls  is  considerably  below  the  temper- 
ature of  the  incoming  steam.  The  fresh  steam  of  high  tempera- 
ture coming  from  the  boiler  comes  in  contact  with  the  walls  of 
the  cylinder  which  have  been  cooled  to  the  temperature  of  the 
exhaust  steam,  and  the  result  is  a  considerable  portion  of  the 
fresh  steam  is  condensed,  the  latent  heat  serving  to  reheat  the 


HANDBOOK   ON   ENGINEERING. 


223 


224  HANDBOOK    ON    ENGINEERING. 

cylinder  walls.  It  will  be  understood  that  were  it  possible  to 
keep  the  cylinder  at  a  higher  temperature,  less  steam  would  be 
condensed  in  warming  it  at  each  stroke  and  consequently  more 
steam  would  be  available  for  useful  work.  In  the  compound 
engine  the  steam  is  expanded  partly  in  one  cylinder  and  partly 
in  the  other  so  that  the  difference  between  the  temperatures  of  the 
incoming  and  exhaust  steam  in  each  cylinder  is  greatly  reduced. 
By  this  means  steam  may  be  expanded  from  a  given  initial  pres- 
sure to  a  given  final  pressure  with  a  loss  of  nearly  twenty-five 
per  cent  less  than  would  be  incurred  were  the  same  expansion  to 
take  place  in  a  single  cylinder.  It  is  due  principally  to  avoiding 
the  loss  by  cylinder  condensation  that  the  compound  engine, 
considered  as  a  type  of  engine,  can  perform  nearly  twenty-five 
per  cent  more  work  with  the  same  weight  of  steam  than  can  be 
obtained  when  the  steam  is  expanded  in  one  cylinder  only. 

In  order  to  utilize  the  low  pressure  steam  escaping  from  the 
high  pressure  cylinder  it  is  necessary  to  provide  a  larger  area 
of  piston  so  that  the  low  pressure  steam  acting  on  a  large  sur- 
face will  do  as  much  work  as  the  high  pressure  steam  acting  on  a 
smaller  area.  It  is  for  this  reason  that  the  low  pressure  cylinder 
of  compound  engines  is  always  made  larger  than  the  high  pressure 
cylinder.  The  required  size  of  low  pressure  cylinder  for  a  given 
size  of  high  pressure,  depends  upon  the  number  of  times  the 
steam  is  to  be  expanded,  the  initial  steam  pressure  and  the  nature 
of  the  work  the  engine  is  intended  for.  For  steady  loads  the 
difference  in  the  size  of  the  two  cylinders  may  be  greater  than 
where  the  load  is  constantly  changing  between  wide  limits  as 
nearly  always  occurs  in  street  railway  service. 

Compound  engines,  as  this  term  is  generally  employed,  are 
built  of  two  types,  the  tandem  compound,  Fig.  145,  and  the  cross 
compound,  Fig.  146.  In  the  tandem  compound  the  work  of  both 
pistons  is  transmitted  to  the  crank  through  one  piston  rod,  cross- 
head  and  connecting  rod,  while  in  the  cross  compound  there  are 


HANDBOOK   ON    ENGINEERING. 


225 


226  HANDBOOK    ON   ENGINEERING. 

two  complete  engines  placed  side  by  side,  the  cranks  of  which 
are  generally  set  90  degrees  apart.  It  will  be  seen  that  in  the 
tandem  compound  engine  it  makes  but  little  difference  from  the 
mechanical  standpoint  whether  the  work  is  divided  evenly  between 
the  two  c}7linders  or  not  because  both  pistons  move  in  unison 
and  drive  the  same  crank.  In  the  cross  compound  engine  it  is 
necessary,  in  order  to  secure  a  uniform  turning  effort  at  the 
shaft,  to  have  the  work  divided  as  nearly  equally  between  the 
two  cylinders  as  the  conditions  will  permit.  In  the  tandem  com- 
pound engine  the  principal  consideration  is  the  proper  working 
of  the  steam,  and  the  sizes  of  the  cylinders  are  determined  by 
the  number  of  expansions  to  be  effected  in  both  cylinders,  or 
the  total  number  of  expansions,  as  it  is  called,  and  the  initial 
pressure.  As  the  equal  division  of  the  work  between  the  two 
cylinders  in  compound  engines  is  essential,  the  ratio  of  the  cylin- 
ders is  generally  for  noncondensing  2i  to  1  for  100  Ibs.,  2J  to  1 
for  125  Ibs.,  and  3  to  1  for  150  Ibs.  initial  pressure,  and  for  con- 
densing 3  to  1  for  100  Ibs.,  3J  to  1  for  125  Ibs.,  and  4  to  1  for 
150  Ibs.,  initial  pressure. 

The  number  of  expansions  required  in  a  compound  engine  is 
represented  by  the  quotient  of  the  absolute  initial  pressure  divided 
by  the  absolute  terminal  pressure.  If  steam  is  to  be  used  at  105 
pounds  gauge  pressure  and  is  to  be  expanded  down  to  10  pounds 

105  +  15 
absolute  in  the  low  pressure  cylinder,  there  will  be r^ =  12 


HANDBOOK   ON   ENGINEERING.  227 

3.2,  equals  ratio  of  cylinders.  Care  should  be  taken  in  non- 
condensing  engines  so  that  the  ratio  of  the  low  pressure  cylinder 
is  not  too  large,  as  in  such  cases  the  steam  in  low  pressure  cylin- 
der would  expand  to  less  than  the  atmospheric  pressure,  and 
thus  make  loops  on  indicator  card  which  would  incur  a  serious 
loss. 

The  calculation  of  the  diameters  of  cylinders  for  a  compound 
condensing  engine  when  the  data  are  given,  follows.  Take  an 
engine  that  is  to  develop  500  horse  power  with  an  initial  pressure 
of  105  pounds  gauge,  or  120  pounds  absolute,  the  steam  to  be 
expanded  to  a  terminal  pressure  of  6  pounds  absolute.  The  total 
expansion  of  steam  in  both  cylinders  is  120  -r-  6  =20. 

Expansion  in  each  cylinder  =  ^/ 20  =4.47. 

Point  of  cut-off  in  each  cylinder,  per  cent  of  stroke  = = 

22.3  per  cent,  1  +  hyp.  log.  of  expansion  in  each  cylinder  =  1  + 
hyp.  log.  4.47  =  2.497. 

Terminal  and  back  pressure  in  high  pressure  cylinder,  and  the 

120 
initial  pressure  in  the  low  =  j^:  =  26.8  pounds. 

Mean  effective  pressure  in  h.  p.  cyl.  =26.8  X2.497 —  26.8 
=  40.11  pounds. 

Mean  effective  pressure  in  1.  p.  cyl.  (assuming  3  Ibs.  back 
press.)  =  6  X  2.497  —  3  =  11.98  pounds. 

If  half  the  work  is  to  be  done  in  each  cylinder,  which  is  de- 
sirable in  cross  compound  engines,  each  cylinder  must  do  250 
horse  power  of  work.  Assuming  the  piston  speed  to  be  600  feet 
per  minute,  the  area  of  the  low  pressure  cylinder  is 

33000  XH.P. 33,000  X  250 

Piston  speed  X  effective  press.  ==  600  X  H-98  =      L47* 7  SqU8 
inches  =38  ins.  diameter. 

33,000  X  250 
Area  of  high  pressure  cylinder  by  same  rule  is :  — I 

OUU  /\  4U.XJ. 

=  342.3  square  inches  =  21  inches  diameter. 


228 


HANDBOOK   ON   ENGINEERING. 


Ratio  of  cyl.  = 


40.11 
11.98 


=  3.3  to  one. 


The  clearance  and  the  areas  of  the  piston  rods  have  not  been 
taken  account  of  by  separate  processes  in  the  foregoing  calcu- 
lations. These  should  always  be  included  when  making  calcu- 
lations involving  the  pressure  and  expansion  of  steam  in  engine 
cylinders.  The  method  of  finding  the  number  of  expansions 
taking  place  in  a  compound  engine  may  be  readily  understood 
by  referring  to  the  diagram,  Fig.  147.  The  shaded  area  in  the 


Fig.  147.    Relative   volume  of   high  and  low  pressure  cylinders. 

smaller  cylinder  represents  the  initial  volume  of  steam  in  the 
high  pressure  cylinder,  that  is  to  say,  this  represents  the  volume 
of  steam  taken  from  the  boiler  for  one  stroke,  or  during  one-half 
revolution.  The  point  of  cut-off  is  at  one-third  stroke  and  the 
area  of  the  low  pressure  cylinder  is  three  times  that  of  the  high 
pressure  cylinder.  It  will  be  seen  that  when  the  low  pressure 
piston  moves  to  one-third  stroke  the  volume  of  the  cylinder  F 
behind  the  piston  is  equal  to  the  volume  of  the  entire  high  pres- 
sure cylinder.  This  shows  that  the  capacity  or  contents  of  the  low 
pressure  cylinder  is  three  times  that  of  the  high  so  that  for  every 


HANDBOOK   ON   ENGINEERING. 


229 


volume  of  steam  and  therefore  for  every  expansion  taking  place  in 
the  high  pressure  cylinder  there  will  be  three  volumes,  and  three 
expansions  taking  place  in  the  low  pressure  cylinder.  This 
shows  why  the  total  number  of  expansions  in  a  compound  engine 
is  the  number  in  the  high  pressure  cylinder  multiplied  by  the 
number  in  the  low  pressure  cylinder.  In  the  diagram,  Fig.  147, 
when  the  small  piston  reaches  the  end  of  the  stroke  the  steam 
will  have  expanded  three  times,  that  is,  it  will  occupy  three  times 
the  space  it  did  at  the  point  of  cut-off.  Now  when  the  large 
piston  reaches  the  end  of  the  stroke  each  of  the  three  volumes  a, 
a  and  a,  Fig.  148,  will  have  been  expanded  three  more  times  and 
the  total  will  be  3  X  3  =  9  expansions,  that  is,  the  original  volume 
a,  Fig.  147,  will  then  occupy  nine  times  the  space  it  did  when 


0 


Fig.  148.    Showing  number  of  expansions  in  both  cylinders. 

first  let  into  the  high  pressure  cylinder.  To  find  the  number  of 
expansions  in  a  compound  engine  multiply  the  number  of  expan- 
sions in  the  high  pressure  cylinder  by  the  number  in  the  low,  or 
multiply  the  number  of  expansions  in  the  high  pressure  cylinder 
by  the  ratio  of  cylinder  areas ;  the  product  will  be  the  number 
required. 

Again  referring  to  Fig.  148,  it  will  be  seen  that  the  low  pressure 
cylinder  must  receive  a  high-pressure  cylinderf  ul  of  steam  at  each 


230  HANDBOOK    ON   ENGINEERING. 

stroke  otherwise  the  pressure  in  the  receiver  and  the  back  pressure 
on  the  high  pressure  piston  will  rise  too  high  and  a  loss  of  power 
will  result,  or  if  the  pressure  be  too  low  in  the  larger  cylinder  the 
small  piston  will  drive  the  larger  one  which  will  again  result  in 
loss  of  power.  It  has  been  shown  that  the  volume  of  both 
cylinders  vary  in  proportion  to  the  areas,  that  is,  if  the  areas  are 
as  1  to  3  then  when  both  pistons  have  reached,  say,  one-third 
stroke  the  volume  of  one  will  be  3  times  the  volume  of  the  other, 
and  when  the  larger  piston  in  this  case  travels  one-third  of  the 
stroke-  the  capacity  of  the  low  pressure  cylinder  behind  the  piston 
will  then  be  equal  to  the  whole  of  the  smaller  cylinder  and  will  be 
capable  of  containing  all  the  steam  used  during  a  full  stroke  of 
the  smaller  piston,  or  a  high-pressure  cylinderful  of  steam.  This 
steam  then  expands  during  the  remaining  two-thirds  of  the  stroke. 
Now  it  will  be  readily  understood  that  if  a  cut-off  valve  were  pro- 


~  Vacuum 

Figs*  149  and  150.    Diagram  from  h.  p.  and  1.  p.  cylinders. 

vided  on  the  low  pressure  cylinder  and  is  set  to  cut  off  at  less  than 
one-third  stroke  (with  a  ratio  of  cylinder  areas  1  to  3)  the  low 
pressure  cylinder  will  not  take  a  high  pressure  cylinderful  of 
steam  when  steam  is  cut  off,  and  the  pressure  in  the  receiver  must 
necessarily  rise.  Reducing  the  volume  of  steam  entering  the  low 
pressure  cylinder  apparently  tends  to  lessen  the  work  done  by  the 
larger  piston  and  consequently  more  work  must  apparently  be 


HANDBOOK   ON   ENGINEERING.  231 

done  by  the  high  pressure  piston.  This  in  turn  causes  a  later 
cut-off  in  the  small  cylinder  as  shown  in  Fig.  149,  dotted  lines, 
which  serves  to  neutralize  the  effect  of  the  higher  back  pressure 
so  that  while  the  cut-off  has  been  made  later,  the  mean  effective 
pressure  remains  practically  the  same.  The  higher  back  pressure 
on  the  small  piston  means  a  higher  initial  pressure  in  the  low 
pressure  cylinder,  see  Fig.  150  dotted  lines,  which  causes  more 
power  to  be  developed  in  the  latter  cylinder.  Thus  it  is  seen 
that,  within  certain  limits,  shortening  the  cut-off  in  the  low  pres- 
sure cylinder  puts  more  of  the  load  upon  the  low  pressure  piston. 

On  the  other  hand  when  the  low  pressure  piston  is  doing  more 
work  than  the  high  pressure,  the  cut-off  in  the  low  pressure 
cylinder  maybe  lengthened.  This  permits  the  low  pressure 
cylinder  taking  more  steam  and  consequently  the  receiver  pressure 
and  the  back  pressure  on  the  high  pressure  piston  are  reduced 
and  the  work  done  by  the  high  pressure  piston  is  thus  increased. 
By  manipulating  the  cut-off  on  the  low  pressure  cylinder  the  load 
on  the  two  pistons  may  be  equalized  or  very  nearly  so  except 
when  the  engine  is  considerably  underloaded  or  overloaded.  The 
range  of  maximum  economy  is  not  as  great  with  the  compound  as 
with  the  simple  engine,  that  is  to  say,  the  loads  :$aay  be  varied 
more  widely  from  the  point  where  the  best  economy  is  obtained, 
in  the  simple  engine  than  in  the  compound  which  is  due  to  the 
large  difference  in  cylinder  areas  in  the  latter  engine.  At  very 
early  cut-off  both  the  high  pressure  and  the  low  pressure  cylinders 
work  the  steam  very  similarly  to  the  simple  engine  and  as  the  loss 
by  cylinder  condensation  increases  with  an  increase  in  the  range 
of  temperatures  it  follows  that  an  underloaded  compound  engine 
is  but  little  if  any  more  economical  than  a  simple  engine  working 
with  a  similar  initial  point  of  cut-off. 

In  compound  automatic  cut-off  engines  the  point  of  cut-off  will 
be  nominally  the  same  in  both  cylinders,  we  say  nominally  (in 
name  only)  because  the  initial  pressure  and  the  extent  of  the 


232  HANDBOOK   ON   ENGINEERING. 

vacuum  have  some  influence  upon  the  receiver  pressure  and  the 
mean  effective  pressure  in  the  low  pressure  cylinder.  In  most 
compound  engines  in  which  the  cut-off  mechanism  of  both  cylin- 
ders are  operated  by  a  single  governor,  provision  is  made  for 
adjusting  the  cut-off  of  the  low  pressure  cylinder  relative  to  that 
in  the  high,  so  that  while  the  nominal  cut-off  may  be,  say,  one- 
fourth  stroke,  the  actual  points  of  cut-off  maybe  one-fourth  in  the 
high  pressure  and  T5^  in  the  low  pressure  cylinder,  the  governor, 
however,  varying  both  points  of  cut-off  as  the  load  changes. 

HORSE  POWER  OF  COMPOUND  ENGINE. 

Little  can  be  done  in  finding  the  horse  power  of  compound  en- 
gines without  the  indicator  because  of  the  uncertainty  of  the  points 
of  cut-off  and  consequently  of  the  back  pressure  and  mean  effec- 
tive pressures.  The  mean  effective  pressure  in  each  cylinder  may 
be  computed  by  using  assumed  data,  by  the  same  rules  given 
for  simple  engines,  but  it  will  readily  be  understood  that  assumed 
data  furnishes  assumed  results  only.  Knowing  the  mean  effective 
pressure  areas  and  speed  of  the  pistons  the  horse  power  of  a 
compound  engine  is  found  as  follows:  Multiply  the  area  of 
the  high  pressure  piston  by  its  mean  effective  pressure  and 
divide  by  the  area  of  the  low  pressure  piston,  then  add  this  quotient 
to  the  mean  effective  pressure  in  the  low  pressure  cylinder.* 
Call  this  answer  1.  Multiply  the  area  of  the  low  pressure 
piston  by  the  piston  speed  in  feet  per  minute  and  by  answer  1, 
and  divide  the  last  product  by  .33, 000;  the  quotient  will  be 
the  indicated  horse  power. 

CONDENSING  ENGINES. 

It  has  been  explained  that  the  atmosphere  exerts  a  pressure 
of  about  15  Ibs.  per  square  inch  on  all  surfaces  with  which  it 


*  This  quantity  is  to  be  taken  as  the  M.  E.  P.  when  finding  steam  con- 
sumption of  compound  engine. 


HANDBOOK    ON    ENGINEERING.  233 

is  in  contact.  The  atmosphere  is  in  contact  with  one  side  of 
an  engine  piston  when  the  exhaust  is  open,  and,  consequently, 
the  steam  in  pushing  the  piston  forward,  has  to  overcome  this 
atmospheric  pressure  of  15  Ibs.  per  square  inch.  The  useful 
pressure  of  steam  is,  therefore,  whatever  pressure  there  is 
above  the  pressure  of  the  atmosphere,  and  this  is  the  pressure 
that  the  steam  gauge  shows.  When  the  gauge  says  60  Ibs.  we 
really  have  75  Ibs.,  but  15  Ibs.  of  it  does  not  count,  because  it 
is  balanced  by  the  atmospheric  pressure  on  the  other  side  of 
the  piston.  If  we  had  sixty-pound  steam  pressing  on  the  pis- 
ton and  could  get  rid  of  the  atmospheric  pressure  on  the  side 
of  the  piston,  the  steam  would  exert  a  force  of  75  Ibs.  per  square 
inch,  a  very  respectable  gain,  indeed.  We  might  remove  the  air 
pressure  by  pumping  it  out,  but  the  amount  of  power  required  in 
doing  the  pumping  would  be  equal  precisely  to  all  gain  hoped  for, 
plus  the  friction  of  the  pump;  therefore,  there  would  be  an 
actual  loss  in  the  operation.  But  there  is  another  way  of  remov- 
ing the  air  pressure.  It  has  been  explained  that  a  cubic  inch  of 
water  vaporizes  and  expands  into  a  cubic  foot  of  steam  at -atmos- 
pheric pressure.  If,  after  getting  this  cubic  foot  of  steam,  we 
take  the  heat  out  of  it,  we  again  turn  it  into  the  cubic  inch  of 
water.  Assume  the  engine  cylinder  to  hold  just  a  cubic  foot  of 
steam,  and  assume  that  the  stroke  is  complete  and  ready  for  the 
exhaust  valve  to  open  and  permit  this  foot  of  steam  to  escape, 
and  assume  that  this  cubic  foot  of  steam  has  expanded 
down  to  atmospheric  pressure,  that  is,  15  Ibs.,  absolute  pressure. 
Now,  instead  of  opening  the  cylinder  to  the  atmosphere,  we  dose 
the  cylinder  with  cold  water.  The  heat  leaves  the  steam  and 
goes  into  the  water  and  the  steam  turns  to  water,  leaving  in  the 
cylinder  the  condensed  steam  in  the  form  of  a  cubic  inch  of 
water.  The  steam  formerly  filled  the  cylinder,  and  now  it  fills 
but  a  cubic  inch  of  it,  consequently,  we  have  produced  in  the 
cylinder  a  vacuum,  which  has  the  effect  of  adding  about  15  Ibs. 


234  HANDBOOK    ON    ENGINEERING. 

per  square  inch,  to  the  force  of  the  steam  on  the  other  side  of  the 
piston,  by  virtue  of  removing  that  much  resistance  to  its  forward 
motion.  The  heat,which  was  in  the  steam, has  gone  into  the  con- 
densing water,  except  the  trifle  that  remains  in  the  cubic  inch  of 
condensed  steam.  We  must  get  this  condensed  steam  out  of  the 
cylinder,  and  it  will  be  an  advantage  to  pump  it  back  into  the 
boiler,  for  it  is  pure  and  it  is  hot. 

This  is  the  general  principle  of  the  condensing  engine.  It 
gives  us  the  grand  advantage  of  a  heavy  increase  in  the  useful 
pressure  acting  to  push  the  piston  forward  ;  it  gives  us  pure 
water  for  use  in  the  boiler,  and  it  saves  in  the  feed- water  the 
heat  that  would  otherwise  go  out  of  the  exhaust  pipe.  But  it  is 
not  practicable  to  condense  the  steam  in  the  cylinder  by  dosing 
the  cylinder  with  cold  water.  In  practice,  the  steam  is  allowed 
to  go  into  a  separate  condensing  vessel,  called  the  condenser. 
The  condenser  is  precisely  the  opposite  of  the  boiler.  The  boiler 
is  the  machine  for  putting  heat  into  the  steam  to  vaporize  it,  and 
the  condenser  is  the  machine  for  taking  heat  out  of  the  steam  and 
turning  it  into  water  again.  In  the  condensing  engine,  one  of 
these  machines  is  pushing  on  the  piston  and  the  other  machine  is 
pulling  on  the  piston.  The  gain  by  condensing  is  so  great  that 
it  is  a  profitable  piece  of  business  to  apply  a  condenser  to  any 
large  non-condensing  engine.  The  condenser  requires  a  pump  to 
withdraw  the  water  of  condensation,  and  this  pump  must  be  in 
reality  an  air-pump.  In  practice,  they  employ  an  air-pump  and 
condenser  combined  in  one  structure,  separate  from  the  engine, 
and  driven  either  by  rod  connection  from  the  engine,  or  by  a  belt 
from  the  engine,  or  by  an  independent  steam  device.  The  arrange- 
ment will  depend  much  upon  the  situation.  The  belt-driven  pump 
permits  of  the  condenser  being  set  in  any  convenient  position 
independent  of  the  engine. 


HANDBOOK    ON    ENGINEERING.  235 


CONDENSERS. 

When  steam  expands  in  the  cylinder  of  a  steam  engine,  its 
pressure  gradually  reduces  and  ultimately  becomes  so  small  that 
it  cannot  profitably  be  used  for  driving  the  piston.  At  this  stage, 
a  time  has  arrived  when  the  attenuated  vapor  should  be  disposed 
of  by  some  method,  so  as  not  to  exert  any  back  pressure  or 
resistance  to  the  return  of  the  piston.  If  there  were  no  atmos- 
pheric pressure,  exhausting  into  the  open  air  would  effect  the 
desired  object.  But,  as  there  is  in  reality  a  pressure  of  about 
14.7  pounds  per  square  inch,  due  to  the  weight  of  the  super- 
incumbent atmosphere,  it  follows  that  steam  in  a  non-condensing 
engine  cannot  economically  be  expanded  below  this  pressure,  and 
must  eventually  be  exhausted  against  the  atmosphere,  which 
exerts  a  back  pressure  to  that  extent. 

It  is  evident  that  if  this  back  pressure  be  removed,  the  engine 
will  not  only  be  aided  by  the  exhausting  side  of  the.  piston  being 
relieved  of  a  resistance  of  14.7  pounds  per  square  inch,  but 
moreover,  as  the  exhaust  or  release  of  the  steam  from  the  engine 
cylinder  will  be  against  no  pressure,  the  steam  can  be  expanded 
in  the  cylinder  quite,  or  nearly,  to  absolute  0  of  pressure,  and 
thus  its  full  expansive  power  can  be  obtained. 

Contact,  in  a  closed  vessel,  with  a  spray  of  cold  water,  or  with 
one  side  of  a  series  of  tubes,  on  the  other  side  of  which  cold 
water  is  circulating,  deprives  the  steam  of  nearly  all  its  latent 
heat,  and  condenses  it.  In  either  case  the  act  of  condensation  is 


236  HANDBOOK    ON    ENGINEERING. 

almost  instantaneous.  A  change  of  state  occurs  and  the  vapor 
steam  is  reduced  to  water.  As  this  water  of  condensation  only 
occupies  about  one  sixteen-hundredths  of  the  space  filled  by 
the  steam  from  which  it  is  formed,  it  follows  that  the  remainder 
of  the  space  is  void  or  vacant,  and  no  pressure  exists.  Now,  the 
expanded  steam  from  the  engine  is  conducted  into  this  empty  or 
vacuous  space,  and,  as  it  meets  with  no  resistance,  the  very  limit 
of  its  usefulness  is  reached. 

The  vessel  in  which  this  condensation  of  steam  takes  place  is 
the  condensing  chamber.  The  cold  water  that  produces  the  con- 
densation is  the  injection  water ;  and  the  heated  water,  on  leaving 
the  condenser,  is  the  discharge  water.  To  make  the  action  of  the 
condensing  apparatus  continuous,  the  flow  of  the  injection  water 
and  the  removal  of  the  discharge  water,  including  the  water  from 
the  liquefaction  of  the  steam,  must  likewise  be  continuous. 

The  vacuum  in  the  condenser  is  not  quite  perfect,  because  the 
cold  injection  water  is  heated  by  the  steam  and  emits  a  vapor  of 
a  tension  due  to  the  temperature.  When  the  temperature  is  110 
degrees  Fahr. ,  the  tension  or  pressure  of  the  vapor  will  be 
represented  by  about  4"  of  mercury ;  that  is,  when  the  mercury  in 
the  ordinary  barometer  stands  at  30",  a  barometer  with  the  space 
above  the  mercury  communicating  with  the  condenser,  will  stand 
at  about  26".  The  imperfection  of  vacuum  is  not  wholly  traceable 
to  the  vapor  in  the  condenser,  but  also  to  the  presence  of  air,  a 
small  quantity  of  which  enters  with  the  injection  water  and  with 
the  steam ;  the  larger  part,  however,  comes  through  air  leaks  and 
faultly  connections  and  badly  packed  stuffing  boxes.  The  air 
would  gradualty  accumulate  until  it  destroyed  the  vacuum,  if 
provision  were  not  made  to  constantly  withdraw  it,  together  with 
the  heated  water  by  means  of  a  pump. 

The  amount  of  water  required  to  thoroughly  condense  the 
steam  from  an  engine  is  dependent  upon  two  conditions :  the  total 
beat  and  volume  of  the  steam,  and  the  temperature  of  the  injection 


HANDBOOK   ON    ENGINEERING. 


237 


water.  The  former  represents  the  work  to  be  done,  and  the  latter 
the  value  of  the  water  by  whose  cooling  agency  the  work  of  con- 
densation of  the  steam  is  to  be  accomplished.  Generally  stated, 
with  26"  vacuum,  the  injection  water  at  ordinary  temperature,  not 
exceeding  70°  Fahr.,  from  20  to  30  times  the  quantity  of  water 
evaporated  in  the  boilers  will  be  required  for  the  complete 
liquefaction  of  the  exhaust  steam.  The  efficiency  of  the  injection 
water  decreases  very  rapidly  as  its  temperature  increases,  and  at 
80°  and  90°  Fahr. ,  very  much  larger  quantities  are  to  be  employed. 
Under  the  conditions  of  common  temperature  of  water  and  a 
vacuum  of  26"  of  mercury,  the  injection  water  necessary  per 
H.  P.  developed  by  the  engine,  will  be  from  1J  gallons  per  minute 
when  the  steam  admission  is  for  one-fourth  of  the  stroke,  up  to 
two  gallons  per  minute,  when  the  steam  is  carried  three-fourths  of 
the  stroke  of  the  engine. 

WEIGHT  OF   WATER   REQUIRED   TO    CONDENSE   1  POUND  OF 

STEAM. 


Temp,  of 
Hot  Well. 

Back  Press, 
in  Cylinder. 
Lbs. 

Temperature  of  Injection  Water,  Degs.  F. 

40 

50 

60 

70 

80 

90 

100 

.94 

17.8 

21.4 

26.8 

35.7 

53.5 

107. 

110 

1.27 

15.1 

17.7 

21.2 

26.5 

35.3 

53. 

120 

1.68 

13.1 

15. 

17.5 

21. 

26.3 

35. 

130 

2.21 

11.6 

13. 

14.9 

17.3 

20.8 

26. 

140 

2.88 

10.3 

11.4 

12.9 

14.7 

17,2 

20.6 

For  other  temperatures  use  the  following  formulas:  — 

JET  CONDENSER.  SURFACE  CONDENSER. 

Weight  of  water  per  Weight  of  water  per 


Ib.  steam  condensed  = 


1170 


Ib.  steam  condensed  = 


H  +  32  —  Ti 


_  ,  .  ti  _  ^ 

In  which  T  =  temperature  of  hot  well,  t  =  temperature  of  the  injec- 
tion water,  TI  =  temp.  of  condensed  steam,  ti  =  temp  of  circulating 
water  leaving,  and  t2,  the  temp,  of  the  circulating  water  entering  the 
condenser,  H  =  total  heat  in  steam  above  32°  F. 


238 


HANDBOOK    ON    ENGINEERING. 


CHANGING  FROM  NONCONDENSING  TO  CONDENSING. 

When  it  becomes  necessary  or  desirable  to  change  a  simple 
noncondensing  engine  to  a  simple  condensing  engine,  or  to  change 
a  compound  noncondensing  to  a  compound  condensing  engine, 
a  slight  change  in  the  adjustment  of  the  exhaust  valves  of  the 
simple  engine  and  of  the  exhaust  valves  on  the  low  pressure  cyl- 
inder of  the  compound  will  in  nearly  all  cases  be  found  necessary 
in  order  to  preserve  the  running  qualities  of  the  engine.  The 
cause  for  this  change  may  be  explained  as  follows :  In  the  first 
place  it  should  be  borne  in  mind  that  the  pressure  of  steam  varies 
inversely  (oppositely)  as  the  volume,  and  that  when  considering 
the  volume  and  pressure  of  steam,  all  pressures  are  taken  or 
measured  above  a  perfect  vacuum  or  above  zero,  in  other  words, 
only  absolute  pressures  are  to  be  considered.  If  10  cubic  feet  of 
steam  at  zero  gauge  pressure,  or  at  atmospheric  pressure,  which 
is  15  pounds  absolute,  be  compressed  into  a  space  containing  5 


2/a,cutttn  Line.. 


Fig.  151.    Showing  point  of  exhaust  closure  non-condensing. 

cubic  feet,  the  pressure  of  the  steam  will  be  raised  to  30  pounds 
absolute,  or  30  —  15  =  15  pounds  by  the  gauge.  Thus  reducing 
toe  volume  one-half  serves  to  double  the  pressure.  It  will  be 


HANDBOOK    ON    ENGINEERING.  239 

understood  that  this  rule  works  both  ways,  namely,  if  the  volume 
be  doubled  the  pressure  will  be  reduced  one-half.  Applying  this 
principle  to  an  engine,  suppose  the  pressure  during  the  return 
stroke  in  Figure  151  is  18  pounds  absolute,  and  that  the  exhaust 
valve  closes  when  the  piston  reaches  the  point  A.  The  volume  of 
steam  entrapped  in  the  cylinder  at  this  point  in  the  stroke  is  taken 
as  the  original  volume.  When  the  piston  moves  to  the  point  B, 
the  volume  will  have  been  reduced  one-half,  and  consequently  the 
pressure  will  have  been  doubled  and  will  have  risen  to  36  pounds. 
When  the  piston  reaches  the  point  (7,  the  volume  will  be  but  one- 
fourth  of  the  original  volume,  and  consequently  the  pressure  will 
be  four  times  the  pressure  of  the  original  volume,  or  18x4  =  72 
pounds  absolute,  or  72  —  15—57  pounds  by  the  gauge.  As  the 
space  x  represents  the  clearance,  the  steam  cannot  be  further 
compressed  so  that  the  pressure  of  compression  in  this  case  is  72 
pounds  absolute,  or  57  pounds  gauge  pressure.  Suppose  that 
the  engine  runs  perfectly  smooth  and  noiselessly  with  that  amount 
of  compression.  If  the  compression  be  increased  or  decreased 
the  engine  will  be  apt  to  pound  and  possibly  to  run  warm.  Now 
suppose  the  engine  be  changed  to  condensing  and  that  the  back 
pressure  be  reduced  to  4  pounds  absolute.  If  the  adjustment  of 
the  exhaust  valves  be  not  changed  compression  will  begin  at  the 
same  point  in  the  return  stroke.  Referring  to  Figure  152,  it  will 
be  seen  by  the  full  lines  that  the  pressure  of  the  original  volume 
is  now  4  pounds  absolute.  When  the  piston  reaches  the  point 
the  volume  will  be  one-half  of  the  original  volume  and  conse- 
quently the  pressure  will  be  doubled,  and  will  now  be  8  pounds 
absolute.  When  the  piston  reaches  the  point  (7,  the  volume  of 
steam  will  be  reduced  to  one-fourth  the  original  volume,  and  the 
pressure  will  be  four  times  the  pressure  of  the  original  volume,  or 
16  pounds  absolute,  which  is  1  pound  by  the  gauge.  It  will  thus 
be  seen  that  if  the  engine  requires  57  pounds  compression  in 
order  to  run  smoothly  it  cannot  be  expected  to  run  smoothly  with 


240 


HANDBOOK    ON  "ENGINEERING. 


only  1  pound  compression  by  the  gauge.  In  order  to  obtain  the 
same  pressure  at  the  end  of  compression  with  steam  of  lower  pres- 
sure the  exhaust  valve  must  close  the  port  earlier  in  the  return 
stroke.  With  the  Corliss  engine  this  may  be  accomplished  by 
adjusting  the  radial  rods  connecting  the  exhaust  valves  with  the 
wrist  plate  and  in  slide  valve  engines  by  adding  exhaust  or  inside 
lap  to  the  valve.  To  find  the  number  of  times  the  volume  of  the 
clearance  x  must  be  increased  in  order  to  lower  the  pressure  from 
72  pounds  to  4  pounds  absolute,  divide  the  pressure  of  compres- 


C  3    A  l/a*,u,K,tn  Line 

Fig.  152.    Showing  point  of  exhaust  closure  condensing. 

sion  by  the  back  pressure  thus  72  -~  4  =  18  times.  Now,  by 
simply  reversing  this  rule  it  will  be  seen  that,  in  order  that  steam  of 
4  pounds  may  be  compressed  to  a  pressure  of  72  pounds  the  volume 
must  be  reduced  to  fa  of  the  original  volume,  therefore  the  origi- 
nal volume  a  must  be  equal  to  18  times  the  volume  of  the  clearance 
space  x  as  shown  by  the  dotted  lines  in  Figure  152.  Now,  when 
the  exhaust  valve  closes  at  a,  Figure  152,  the  pressure  is  4 
pounds ;  at  b  the  volume  is  but  one-half,  and  the  pressure  8 
pounds  ;  at  c  the  volume  is  one-fourth  and  the  pressure  16  pounds  ; 
at  d  the  volume  is  -j^  °f  the  original  volume  a,  and  the  pressure 
is  18x4  =^72  pounds,  which  is  the  pressure  required  for  smooth 


HANDBOOK    ON    ENGINEERING.  241 

running.  It  will  thus  be  seen  that  the  same  pressures  are  required 
whether  running  noncondensing  or  condensing,  and  that  in  order 
to  get  the  same  pressure  of  compression  when  running  condens- 
ing as  when  running  noncondensing,  the  exhaust  valve  must  close 
earlier  in  the  return  stroke. 

It  will  also  be  understood  that  when  changing  from  condens- 
ing to  noncondensing  the  order  of  things  must  be  reversed,  viz., 
the  exhaust  valve  must  close  the  port  later  in  the  return  stroke 
because  the  higher  the  back  pressure,  the  greater  will  be  the 
pressure  of  compression.  This  explains  why  a  condensing  engine 
pounds  and  heats  when  the  vacuum  becomes  impaired  or  is  lost 
altogether.  In  this  case  the  back  pressure  rises  from  that 
obtained  when  running  condensing  to  the  pressure  obtained  non- 
condensing  and  consequently  the  compression  is  much  too  high 
for  smooth  running.  On  the  other  hand  when  changing  from 
noncondensing  to  condensing  the  back  pressure  is  so  low  that 
scarcely  any  compression  can  be  obtained,  and  if  the  engine 
requires  considerable  compression  it  is  apt  to  pound  and  heat 
when  the  change  is  made  provided  the  exhaust  valves  are  not 
readjusted. 

It  frequently  happens  that  the  change  from  noncondensing  to 
condensing  is  made  at  the  end  of  the  week,  and  in  this  case  it  is 
desirable  to  adjust  the  valves  on  Sunday  to  their  approximate 
position  by  means  of  the  marks  on  the  valves,  so  as  to  avoid,  as 
far  as  possible,  any  trouble  when  starting  up  on  Monday  morn- 
ing. Under  these  circumstances  it  is  desirable  to  estimate  the 
extent  of  the  change  necessary  in  the  adjustment  of  the  valves. 
Multiply  the  length  of  the  stroke  in  inches  by  the  percentage  of 
clearance  and  by  one-fourth  the  absolute  pressure  of  compression 
when  running  noncondensing ;  this  product  is  the  approximate 
point  of  exhaust  closure  when  running  condensing.  Then 
lay  off  this  distance,  beginning  at  the  ends  of  the  guides. 
When  the  crosshead  is  within  this  distance  of  the  end  of 

16 


242  HANDBOOK    ON    ENGINEERING. 

the  return  stroke,  the  exhaust  valve  should  have  just 
closed  the  port.  For  illustration,  suppose  an  18x42  Corliss 
engine  is  to  be  changed  from  noncondensing  to  condensing.  The 
clearance  is  3  per  cent  and  the  pressure  of  compression  is  44 
pounds  absolute.  The  clearance  is  equal  to  42x.03  =  1.26  inches 
of  the  stroke,  and  one-fourth  of  the  pressure  of  compression 
when  running  noncondensing  is  44  -v-  4  =  11  pounds,  so  that  the 
distance  to  be  laid  off  on  the  guides  is  1.26x11  =  13.86  or  13| 
inches,  that  is,  when  the  back  pressure  is  reduced  to  4  pounds 
absolute  by  the  condenser,  the  exhaust  valve  should  close  when 
the  piston  reaches  a  point  13 £  inches  from  the  ends  of  the  return 
stroke  in  order  to  obtain  approximately  the  same  compression  as 
when  running  noncondensing. 

It  will  be  understood  that  this  is  merely  a  method  of  approxi- 
mating the  pressure  and  should  not  be  relied  upon  except  for 
making  temporary  adjustments. 

The  only  reliable  method  of  setting  the  exhaust  valves  when 
making  changes  of  this  kind  is  by  means  of  the  indicator  be- 
cause the  pressures  vary  from  several  causes  the  effect  of  which 
cannot  be  calculated  with  a  sufficient  degree  of  accuracy  for  this 
purpose.  This  is  true  of  both  the  simple  and  compound  engines, 
the  same  method  being  used  with  the  low  pressure  cylinder  of  the 
compound  as  with  the  simple  or  single  cylinder  engine. 

TYPES  OF  CONDENSER. 

Condensers  may  be  divided  into  three  general  types  or  classes 
known  as  the  surface,  the  jet  and  the  siphon  condensers.  The 
latter  type  is  sometimes  referred  to  as  the  barometric  condenser. 
The  surface  and  jet  condensers  require  an  air  pump  and  these  two 
types  are  either  direct  driven  or  independent.  The  direct  driven 
condenser  is  now  little  used  for  stationary  work,  being  confined 
almost  entirely  to  marine  engines,  and  even  there  the  independent 


HANDBOOK   ON    ENGINEERING.  243 

condenser  is  being  very  extensively  used.  The  direct  connected 
condenser  is  driven  either  by  a  belt  or  a  direct  connection  to  the 
crosshead  of  the  main  engine.  The  working  vacuum  is  not  obtain- 
able in  the  direct  connected  condenser  until  after  the  engine  is  started 
and  has  made  several  revolutions.  The  disadvantage  of  the  direct 
connected  condenser  is  that  the  speed  is  always  proportional  to 
the  speed  of  the  engine  so  that  the  vacuum  can  only  be  regulated 
by  changing  the  supply  of  injection  or  circulating  water  as  the 
case  may  be.  The  independent  condensers  are  driven  by  a  steam 
cylinder  forming  a  part  of  the  condenser  apparatus  so  that  the 
vacuum  can  be  maintained  by  regulating  the  supply  of  condensing 
water,  and  also  by  changing  the  speed  of  the  air  pump  irrespec- 
tive of  the  speed  of  the  engine.  The  greater  flexibility  of  the 
independent  condenser  enables  it  to  maintain  the  working  vacuum 
under  widely  changing  loads  and  speeds.  The  cost  of  operating 
the  latter  type  of  condenser  is  greater  than  of  the  direct  driven 
types  because  the  power  required  for  direct  driving  is  obtained  at 
the  same  cost  per  horsepower  as  that  delivered  by  the  engine, 
while  the  cost  of  operating  the  independent  condenser  is  practi- 
cally the  same  as  that  of  an  ordinary  steam  pump.  This  apparent 
loss  can  be  largely  avoided  by  utilizing  the  exhaust  steam  from 
the  condenser  for  heating  the  feed  water. 

The  following  illustrations  represent  the  three  principal  con- 
structions of  condenser  to  be  found  in  the  average  stationary 
practice. 

A  sectional  view  of  the  surface  condenser  with  air  and  circu- 
lating pumps  attached  is  shown  in  Fig.  153.  It  consists  of  a 
shell,  usually  of  cast  iron,  containing  a  large  number  of  small 
brass  or  copper  tubes  through  which  the  condensing,  or  circulat- 
ing water  as  it  is  called,  is  pumped  by  the  circulating  pump. 
The  water  enters  the  chamber  at  one  end  of  the  condensing 
chamber  and  flows  through  one  bank  of  tubes  into  a  chamber  at 
the  opposite  end  and  thence  back  again  and  out  at  the  top  into 


244 


HANDBOOK    ON    ENGINEERING. 


the  discharge  pipe.  The  steam  enters  the  condensing  chamber 
at  the  top  where  the  current  is  divided  by  a  baffle  plate,  which 
sends  the  steam  in  both  directions  and  distributes  it  more  evenly 
over  the  cool  tubes,  the  steam  being  condensed  by  coming  in 
contact  with  the  tubes,  the  temperature  of  which  is  the  same  as 
that  of  the  circulating  water  flowing  through  them.  The  con- 
densed steam  collects  in  the  bottom  of  the  condensing  chamber 
and  flows  into  the  suction  pipe  of  the  air  pump,  which  also  removes 
the  air  and  aids  in  maintaining  the  vacuum.  The  steam  cylinder 


Fig.  158.    Diagram  of  Surface  Condenser. 

is  placed   between   the   air  and  circulating  pumps,  the  pistons 
being  connected  to  the  same  piston  rod. 

Surface  condensers  embody  two  constructions  or  arrangements 
of  tubes.  In  one  the  tubes  are  connected  to  tube  plates,  the 
arrangement  being  similar  in  every  way  to  the  return  tubular 
boiler.  The  other  construction  is  known  as  the  double  tube  con- 
denser in  which  two  sets  of  tubes  are  employed,  one  within  the 
other  as  shown  in  Fig.  153.  The  circulating  water  flows  through 


HANDBOOK    ON    ENGINEERING.  245 

the  inner  tubes  and  returns  through  the  outer  or  larger  ones. 
This  construction  has  the  advantage  in  that  the  outer  tubes  are 
kept  at  practically  the  same  temperature  throughout  their  length, 
thus  increasing  the  efficiency  of  the  tube  surface.  Water  will 
absorb  heat  more  rapidly  when  flowing  at  a  high  velocity  than  at 
a  low  velocity,  consequently  the  double  tube  condenser  can  be 
made  smaller  for  a  given  capacity  than  the  single  tube  type.  The 
air  pump  discharges  into  the  hot  well,  and  as  the  circulating 
water  does  not  come  in  contact  with  the  steam,  either  before  or 
after  it  is  condensed,  the  water  in  the  hot  well  is  always  pure,  or 
nearly  so,  and  suitable  for  use  in  the  boilers.  When  the  surface 
condenser  is  employed  the  steam  passes  from  the  low  pressure 
cylinder  into  the  hot  well  and  consequently  some  provision  should 
be  made  for  removing  the  oil  from  the  exhaust  steam.  Greasy 
condenser  tubes  are  not  as  efficient  as  clean  ones  and  for  this 
reason  it  is  advisable  to  place  the  oil  extractor  between  the  low 
pressure  cylinder  and  the  condenser.  Any  oil  that  may  pass 
through  the  extractor  and  into  the  hot  well  may  be  avoided  by 
taking  the  supply  to  the  boiler  feed  pump  at  a  point  below  the 
surface  of  the  water  in  the  hot  well. 

The  surface  condenser  is  particularly  valuable  where  the  water 
is  unfit  for  use  in  the  boilers  and  for  this  reason  it  is  used  more 
largely  for  marine  than  for  stationary  work. 

The  surface  condenser  furnishes  the  more  reliable  means  of 
measuring  the  steam  consumption  of  engines  and  pumps  because 
the  discharge  of  the  air  pump  in  a  given  time  represents  exactly 
the  quantity  of  water  required  by  the  engine  in  the  same  length 
of  time. 

Fig.  154  is  a  sectional  view  of  the  independent  jet  condenser. 
The  external  appearance,  and  sometimes  the  minor  details  of  con- 
struction, will  vary  slightly  in  this  style  of  condenser  but  it  is 
fortunate  for  engineers  that  the  principles  involved  and  the 
practical  operation  of  jet  condensers  are  precisely  the  same  in  all. 


246 


HANDBOOK    ON    ENGINEERING. 


The  steam  and  water  cylinders  and  valves  of  the  jet  condenser 
are  identical  to  similar  parts  of  the  ordinary  direct  acting  pump, 
in  fact,  the  jet  condenser  is  a  direct  acting  pump  with  a  simple 
condensing  chamber  connected  to  the  pump  suction.  The  con- 
densing chamber  resembles  an  air  chamber  in  form,  except  that  it 


Fig.  154.    Independent  Jet   Condenser. 

is  larger,  and  it  is  provided  with  an  inlet  for  the  exhaust  steam 
and  an  outlet  for  the  injection  or  condensing  water.  The  inlet 
for  the  water  is  carried  down  to  the  spherical  part  of  the  condens- 
ing chamber  and  terminates  in  a  cone-shaped  spraying  device, 
which  throws  the  water  out  in  an  umbrella-shaped  film  against 
the  sides  of  the  chamber.  The  exhaust  steam  enters  above  the 


HANDBOOK    ON    ENGINEERING.  247 

, 

spray  and  cannot  reach  the  pump  below  without  passing  into  the 
spray  of  cold  water,  which  condenses  it.  The  mixture  of  con- 
densed steam  and  injection  water  is  then  drawn  into  the  pump 
and  is  finally  discharged  into  the  hot  well.  The  admixture  of 
the  condensed-  steam  with  the  injection  water  improves  the  quality 
of  the  water  in  the  hot  well,  provided  means  are  employed  for 
removing  the  oil  from  the  exhaust  steam,  thus  rendering  the  water 
better  fitted  for  use  in  the  boilers.  The  injection  water  is 
regulated  by  means  of  a  hand  wheel  at  the  top  of  the  condensing 
chamber  which  regulates  the  position  of  the  cone  at  the  end  of  the 
water  inlet. 

When  engines  are  lightly  loaded,  or  liable  to  be  for  any  length 
of  time,  it  is  especially  desirable  to  provide  a  safety  device  which 


Tig.  155.    Device  for  Breaking  the  Vacuum. 

will  break  the  vacuum  when  the  water  rises  to  a  certain  height  in 
the  condensing  chamber.  If  this  is  not  done  injury  to  the  engine 
is  liable  to  occur  at  any  time  because  should  the  speed  of  the 
pump  slacken,  thus  permitting  water  to  accumulate  in  the  con- 
densing chamber,  the  vacuum  will  be  impaired  and  the  low 

• 


248 


HANDBOOK    ON    ENGINEERING. 


pressure  cylinder  will  then  act  as  an  air  pump,  owing  to  the  small 
amount  of  steam  admitted  and  the  low  pressure  due  to  expansion, 
and  will  thus  draw  the  water  into  the  cylinder  probably  wrecking 
the  cylinder  completely.  A  simple  safety  device  adapted  to  pre- 
vent injury  to  the  engine  as  the  result  of  flooding  the  condenser 
is  illustrated  in  Fig.  155.  It  consists  of  a  simple  float  con- 


Fig.  156.    Method  of  connecting  up  a  Jet  Condenser. 

nected  to  an  air  valve  at  the  side  of  the  condensing  chamber  so 
that  when  the  water  level  rises  high  enough  to  raise  the  float,  air 
is  admitted  and  the  vacuum  immediately  destroyed.  The  ex- 
haust steam  from  the  engine  then  flows  out  through  the  atmos- 
pheric relief  valve  into  the  atmosphere,  and  the  engine  is  con- 


HANDBOOK    ON    ENGINEERING.  249 

verted  into  a  noncondensing   engine   automatically  and  without 
stopping. 

Jet  condensers  will  raise  water  for  condensing  purposes  from  16 
to  20  feet  although  it  is  desirable  to  keep  the  lift  as  low  as  pos- 
sible because  the  higher  the  lift,  the  more  it  costs  to  operate  the 
condenser  and  consequently  the  net  saving  by  running  condensing 
is  correspondingly  less. 

The  jet  condenser  requires  precisely  the  same  care  as  the  direct 
acting  pump  except  that  greater  pains  must  be  taken  to  prevent 
the  leakage  of  air  and  water.  An  engineer  who  can  keep  a  direct 
acting  pump  in  first-class  running  order  need  have  little  trouble 
in  caring  for  a  condenser  whether  it  be  large  or  small. 

Fig.  156  illustrates  the  method  of  connecting  the  jet  condenser 
with  the  engine.  When  the  exhaust  steam  from  the  condenser 
cannot  be  profitably  used  for  heating  the  feed  water  it  can  be 
turned  into  the  engine  exhaust  pipe,  or  into  the  condensing 
chamber  direct,  and  the  condenser  thus  be  made  to  run  condens- 
ing also. 

The  siphon  condenser  is  illustrated  in  Fig.  157,  and  is  the 
simplest  form  of  condenser  in  use  at  the  present  time.  The 
exhaust  steam  enters  the  somewhat  contracted  condensing  cham- 
ber through  the  cone-shaped  nozzle,  while  the  condensing  water 
enters  at  the  side  and  surrounds  the  cone,  the  water  issuing  into 
the  chamber  below  through  the  annular  orifice  formed  between 
the  cone  and  the  walls  of  the  condensing  chamber.  The  water 
issues  at  rather  high  velocity  and  expels  the  air  from  the  exhaust 
pipe.  The  steam  upon  leaving  the  cone-shaped  nozzle  flows  into 
an  inverted  cone,  formed  by  the  film  of  water  issuing  from  the 
annular  orifice  which  condenses  the  steam.  The  condensed  steam 
and  injection  water  flow  at  rather  high  velocity  down  through  the 
contracted  neck,  where  the  stream  is  solidified,  into  the  tail  pipe, 
thence  into  the  hot  well.  The  neck  of  the  condensing  chamber  is 
contracted,  thus  forming  a  combining  tube,  for  the  purpose,  of 


250 


HANDBOOK    ON    ENGINEERING. 


giving  the  water  sufficient  velocity  to  maintain  a  siphon-like 
action  that  draws  the  steam  from  the  exhaust  pipe  and  causes  a 
vacuum  to  exist  in  it.  This  style  of  condenser  should  be  placed 
34  feet  above  the  level  of  the  water  in  the  hot  well.  An  atmos- 
pheric discharge  or  relief  valve  is  placed  at  the  top  which 
opens  automatically  when  the  vacuum  is  destroyed  thus  permit- 
ting the  exhaust  steam  to  flow  into  the  atmosphere.  The  siphon 


Fig.  157.    Siphon  Condenser. 

condenser  will  raise  the  condensing  water  to  a  height  of  from  15 
to  18  feet  so  that  when  the  water  supply  is  located  within  that 
distance  of  the  top  of  the  condenser  no  pump  is  required,  the 
condenser  continuing  to  siphon  over  the  water  as  long  as  steam 
is  condensed.  When  the  condenser  is  operated  without  a  pump 
a  starting  pipe  will  be  necessary ;  this  pipe  connecting  the  water 
supply  with  the  tail  pipe  as  shown  in  Fig.  158.  When  starting 
the  condenser,  the  valve  in  the  starting  pipe  is  opened,  and  the 


HANDBOOK    ON    ENGINEERING. 


251 


water  flowing  through  this  and  down  the  tail  pipe  will  gradually 
exhaust  the  air  from  the  upper  part  of  the  tail  pipe  until  sufficient 
vacuum  is  formed  to  draw  the  water  up  to  the  condenser  and 
start  the  water  flowing  through  it.  When  this  is  done  the  valve 
in  the  starting  pipe  is  closed,  and  the  engine  started. 


Fig.  158.    Siphon  Condenser  and  Starting  Talve. 

Fig.  159  shows  the  method  of  connecting  a  siphon  condenser 
with  the  engine.  In  this  illustration  the  condensing  water  is 
supplied  by  a  pump. 

It  frequently  becomes  necessary  to  destroy  the  vacuum  and  to 
stop  the  engine  on  short  notice,  and  for  this  reason  it  is  desirable 
to  have  some  means  of  opening  the  atmospheric  relief  valve  at  the 
top  of  the  condenser.  This  is  especially  desirable  when  the  con- 
denser is  arranged  to  siphon  the  water  because  any  failure  of  the 
condenser  with  a  light  load  on  the  engine  would  result  in  water 
being  drawn  into  the  low  pressure  cylinder  and  probably  wrecking 
it.  An  arrangement  for  thus  breaking  the  vacuum  is  shown  in 
Fig.  159. 

The  water  in  the  hot  well  consists  of  a  mixture  of  condensing 


252 


HANDBOOK    ON    ENGINEERING. 


water  and  condensed  steam  so  that  if  the  water  is  to  be  used  in 
the  boilers  means  should  be  provided  for  removing  the  oil  from 
the  exhaust  steam,  and  the  supply  to  the  boiler  feed  pump 


Fig.  159.    Siphon  Condenser  connected  to  Engine  and  Pump. 

should  be  taken  at  a  point  considerably  below  the  water  level  in 
the  hot  well. 

The  siphon  condenser,  when  properly  proportioned  and  con- 
nected up  maintains  a  good  vacuum  and  possesses  the  advantage 


HANDBOOK    ON    ENGINEERING.  253 

that  it  contains  no  moving  parts  and  nothing  to  get  out  of  order, 
while  it  is  adapted  to  engines  of  all  sizes,  and  under  all  condi- 
tions which  will  permit  it  to  be  elevated  to  a  height  of  34  feet 
above  the  level  of  the  water  in  the  hot  well. 

The  quantity  of  condensing  water  required  by  the  siphon  con- 
denser is  the  same  as  for  the  jet  condenser  and  may  be  found  by 
means  of  the  formulas  on  page  237. 

STARTING  AND  RUNNING  A  COMPOUND  CONDENSING 
ENGINE. 

The  principal  aim  of  the  engineer  in  charge  of  a  plant  is  to 
keep  his  engine  running,  and  to  run  safely,  and  when  running 
condensing  the  object  also  is  to  maintain  the  vacuum.  The 
vacuum  is  formed  by  removing  the  air  from  the  exhaust  pipe  and 
its  immediate  connections,  including  the  condenser.  Therefore 
when  air  leaks  in  or  is  admitted  through  a  valve  either  intentionally 
or  otherwise  the  vacuum  will  at  once  be  destroyed.  It  will  be 
understood  from  this  that  all  air  leaks  should  be  carefully  stopped. 
The  principal  points  to  receive  attention  when  testing  for  air  leaks 
are,  the  stuffing  boxes  on  both  the  engine  and  the  condenser,  and 
also  on  the  valves  in  pipes  leading  to  and  from  the  condenser. 
A  condensing  engine  and  its  condenser  should  be  provided  with 
a  solid  foundation  and  be  securely  bolted  to  it.  Vibration  in  the 
piping  is  a  common  cause  of  leaky  joints,  and  air  leaks  will  affect 
the  vacuum  very  seriously.  It  is  a  good  plan  to  test  the  exhaust 
and  condenser  piping  occasionally  while  the  engine  is  running. 
A  lighted  candle  held  close  to  the  joints  will  serve  to  locate  aleak, 
which  should  be  marked  with  a  piece  of  chalk  so  as  to  be  readily 
found  when  an  opportunity  occurs  to  make  repairs. 

The  vacuum  may  be  reduced  and  even  destroyed  by  too  much 
water  as  well  as  by  too  little.  When  too  little  water  is  admitted 
all  the  steam  is  not  condensed,  and  the  accumulation  of  uncon- 


254  HANDBOOK    ON    ENGINEERING. 

densed  steam  raises  the  pressure  in  the  condenser  until  finally  the 
back  pressure  valve  opens  and  the  engine  exhausts  into  the  atmos- 
phere and,  of  course,  becomes  a  noncondensing  engine.  When 
too  much  water  is  admitted  the  air  pump  becomes  flooded,  the 
volume  of  the  condenser  is  decreased, .the  injection  interfered  with, 
and  air  gradually  accumulates,  causing  the  vacuum  to  become 
less,  sometimes  rapidly  and  at  others  quite  gradually  depending 
on  the  excess  of  water. 

The  condenser  should  be  run  at  as  low  a  speed  as  possible  and  be 
able  to  discharge  the  necessary  quantity  of  water,  and  to  main- 
tain the  required  vacuum.  When  air  leaks  occur  the  speed  of  the 
condenser  must  be  increased  with  the  same  load  on  the  engine 
and  with  other  conditions  the  same,  so  that  when  it  becomes  nec- 
essary to  gradually  increase  the  speed  it  indicates  that  leakage  is 
occurring  either  at  some  point  in  the  exhaust  piping,  in  the  in- 
jection pipe  leading  to  the  condenser  or  in  the  valves  or  piston  in 
the  condenser  itself.  It  is  not  profitable  to  allow  the  packing  in 
the  stuffing  boxes  on  the  engine  and  condenser,  and  on  the  valves 
in  the  piping,  to  remain  as  long  as  it  will  apparently  work  air  tight 
because  when  old  packing  begins  to  give  out  it  generally  becomes 
useless  in  a  very  short  time,  and,  furthermore,  it  seldom  admits 
of  any  adjustment  with  beneficial  results.  It  is  better  to  renew 
the  packing  at  shorter  intervals  and  know  that  when  a  gland  is 
tightened  the  leakage  will  be  stopped. 

Generally  speaking  the  higher  the  vacuum  the  better,  but  this 
is  not  always  true.  When  engines  are  very  lightly  loaded  and  have 
but  little  resistance  above  that  due  to  friction,  it  is  sometimes 
better  economy  to  reduce  the  vacuum,  thus  slightly  increasing  the 
period  of  admission,  because  the  engine  uses  steam  expansively 
and  the  condenser  does  not,  so  that  a  part  of  the  steam  required 
by  the  condenser  can  be  used  to  better  advantage  in  the  engine 
cylinder.  It  sometimes  occurs  that  the  boilers  are  too  small, 
and  where  an  exhaust  steam  feed  water  heater  is  placed  in  the 


• 

HANDBOOK    ON    ENGINEERING.  255 

low  pressure  exhaust  pipe  it  will  frequently  be  found  more  eco- 
nomical to  reduce  the  vacuum  and  thus  send  the  feed  water  to 
the  boilers  at  a  higher  temperature.  The  regulation  of  the  vacuum 
under  ordinary  conditions  should  be  governed  by  the  position  of 
the  governor  as  well  as  by  the  vacuum  gauge,  the  object  being  to 
maintain  a  vacuum  that  will  keep  the  governor  at  the  highest 
position.  Under  certain  conditions  of  load  the  cut-off  will  be 
found  to  be  shorter  with  26  inches  than  with  27  or  28  inches 
vacuum.  The  receiver  pressure  also  has  something  to  do  with 
the  position  of  the  governor.  The  receiver  is  usually  a  plain 
metal  cylinder  placed  beneath  the  engine  room  floor,  and  to  which 
the  exhaust  pipe  from  the  high  pressure  cylinder  and  the  steam  pipe 
to  the  low  pressure  cylinder  are  connected.  The  high  pressure 
cylinder  exhausts  into  the  receiver  and  the  low  pressure  cylinder 
takes  its  steam  from  the  receiver.  It  will  be  understood  from 
this  that  the  receiver  virtually  serves  as  the  boiler  for  the  low 
pressure  cylinder.  The  pressure  in  the  receiver  is  generally  a 
little  lower  than  the  terminal  pressure  in  the  high  pressure  cylin- 
der, while  the  receiver  pressure  and  the  initial  pressure  in  the  low 
pressure  cylinder  are  practically  the  same. 

What  is  known  as  a  reheater,  which  is  sometimes  used  in  con- 
nection with  compound  engines,  is  merely  a  coil  of  steam  pipe 
placed  in  the  receiver,  steam  of  higher  temperature  than  that  of 
the  exhaust  from  the  high  pressure  cylinder  being  admitted  to  the 
coil  which  heats  the  steam  in  the  receiver  to  a  temperature  higher 
than  that  due  to  the  pressure,  thus  serving  to  reduce  the  loss  due 
to  condensation  in  the  low  pressure  cylinder,  and  incidentally 
improving  the  economy  of  the  engine  as  a  whole.  Changing  the 
receiver  pressure  will  oftentimes  alter  the  position  of  the  governor 
by  improving  the  distribution  of  the  load  between  the  high  and 
low  pressure  cylinders.  It  should  be  remembered  in  this  con- 
nection that  lengthening  the  point  of  cut-off  in  the  low  pressure 
cylinder  reduces  the  receiver  pressure  and  consequently  tends  to 


256  HANDBOOK    ON    ENGINEERING. 

throw  more  of  the  load  on  the  high  pressure  cylinder,  while  short- 
ening the  cut-off  in  the  low  pressure  cylinder  tends  to  throw  more 
of  the  load  on  to  the  low  pressure  cylinder.  The  receiver  pressure 
is  governed  by  two  things,  viz.,  the  amount  of  steam  put  into  it, 
and  the  amount  of  steam  drawn  out  of  it.  If  the  low  pressure 
cylinder  draws  more  out  of  it  than  the  higher  pressure  cylinder 
puts  into  it,  the  pressure  must  fall  because  the  volume  is  thus  in- 
creased. Engine  cylinders  are  generally  so  proportioned  that  the 
receiver  pressure  will  be  from  4  to  6  pounds  lower  than  the  ter- 
minal pressure  in  the  high  pressure  cylinder  when  the  engine  has 
a  fair  load.  When  an  engineer  knows  what  the  terminal  pressure 
in  the  high  pressure  cylinder  is  it  is  not  difficult  to  set  the  cut-offs 
to  produce  the  desired  results.  When  the  high  pressure  exhaust 
valves  pound  and  lift  from  the  seats  it  may  be  safely  assumed  that 
the  receiver  pressure  is  higher  than  need  be,  and  it  will  generally 
be  found  practicable  to  lessen  the  pressure,  which  may  be  done 
by  lengthening  the  period  of  admission  in  the  low  pressure  cylin- 
der, being  careful  to  note  exactly  the  extent  of  the  adjustment 
because  there  is  the  possibility  of  other  things  causing  the  valves 
to  pound,  and  in  that  case  the  cut-off  should  be  shortened  again 
exactly  the  same  amount  to  which  it  had  been  lengthened. 

For  usual  ratios  of  cylinder  volumes,  viz.,  from  3  to  1  or  4  to 
1,  and  under  average  conditions  of  load  on  condensing  engines, 
a  boiler  pressure  of  80  or  90  pounds  will  produce  a  receiver  pres- 
sure of  about  5  pounds ;  100  pounds  will  produce  from  7  to  10 
pounds;  125  pounds  from  12  to  15,  and  150  pounds  from  18  to 
20  pounds.  The  receiver  pressure  frequently  rises  from  1  to  3 
pounds  with  changes  of  load. 

The  best  results  are  generally  obtained  when  the  load  is  equally 
divided  between  the  high  and  low  pressure  cylinders.  The  gov- 
ernor should  thus  remain  at  the  highest  obtainable  point  with  any 
given  load  and  with  a  moderately  high  vacuum,  say  26  or  26 £ 
inches.  The  extent  of  changes  to  produce  these  results  cannot 


HANDBOOK    ON    ENGINEERING.  257 

be   foretold,  but   must    be   ascertained  by  experiment  in  each 
case. 

When  about  to  start  a  compound  condensing  engine  the  first 
thing  to  be  done  is  to  see  that  all  the  water  is  drained  out  of  the 
piping.  If  the  engine  is  a  Corliss  or  other  four-valve  engine  the 
high*  pressure  cylinder  will  readily  get  rid  of  the  water,  but  this 
water  drains  into  the  receiver,  and  if  not  removed  will  enter  the 
low  pressure  cylinder  when  the  engine  is  started,  and  probably 
wreck  it.  If  there  is  a  separator  it  should  be  carefully  drained. 

Then  the  pipe  above  the  engine  throttle,  then  the  cylinder  and 
lastly  the  receiver.  If  these  parts  are  thoroughly  drained  before 
starting,  what  little  water  may  enter  the  low  pressure  cylinder, 
due  to  condensation  in  the  high  pressure  cylinder  and  receiver, 
will  cause  no  trouble  or  damage  provided  the  engine  is  started 
slowly  so  as  to  give  the  water  time  to  pass  out  through  the  exhaust 
ports.  The  steam  line  to  the  condenser  should  also  be  drained 
down  to  the  condenser  throttle  so  that  when  it  is  time  to  start  the 
condenser  it  can  be  done  without  delay. 

About  20  minutes  before  time  for  starting  the  plant  begin  to 
warm  the  cylinders.  Place  the  wrist  plates  at  their  central  posi- 
tion. Open  the  throttle  a  little  and  also  the  live  steam  valve  to 
the  receiver.  Allow  the  receiver  drain  to  remain  open  a  little 
until  after  starting.  Then  open  the  oil  cups  and  the  cylinder 
lubricators  and  see  that  they  are  feeding  the  proper  quantity  of 
oil. 

If  it  is  not  desirable  for  any  reason  to  start  the  engine  in 
advance  of  the  other  machinery,  the  wrist  plates  can  be  worked 
back  and  forth  a  few  times  by  hand,  after  which  the  throttle  and 
receiver  valve  should  be  closed,  leaving  the  wrist  plates  in  the 
central  position.  A  little  practice  will  indicate  how  wide  the 
throttle  can  be  opened  and  how  high  the  receiver  pressure  may  be 
allowed  to  rise  without  moving  the  engine  when  working  the 
wrist  plates.  After  warming  the  cylinders,  the  condenser  may  be 

17 


258  HANDBOOK    ON    ENGINEERING. 

started.  If  the  air  pump  is  in  proper  running  order  the  vacuum 
gauge  will  soon  indicate  the  vacuum,  which  ought  to  be  increased  to 
about  25  inches.  If  the  exhaust  from  the  steam  cylinder  of  the 
condenser  is  run  into  the  condensing  chamber,  the  injection  water 
should  be  turned  on  after  the  air  pump  has  made  three  or  four 
strokes,  otherwise  the  injection  water  may  be  turned  on  immediately 
upon  starting  the  engine,  or  before  if  desired.  When  the  run- 
ning position  of  the  injection  valve  is  not  known  it  may  be  tried  at 
from  one-half  to  two-thirds  open.  When  the  air  pump  is  running 
properly  inspect  the  overflow  to  see  that  the  water  is  discharged 
properly  and  freely.  Considerable  water  will  be  discharged  from 
the  condenser  if  the  injection  valve  is  open  and  the  condenser  is 
working  properly. 

Returning  to  the  engine,  hook  in  the  low  pressure  reach  rod 
and  then  the  high  pressure.  Then  open  the  throttle  a  little  and 
start  the  engine  slowly  so  that  any  slight  condensation  which 
may  have  accumulated  can  be  worked  out  more  slowly.  After 
the  engine  has  made  one  or  two  revolutions  attention  should  be 
paid  to  the  vacuum  gauge  to  see  that  the  condenser  is  getting  the 
proper  amount  of  water.  It  is  probable  the  injection  valve  will 
have  to  be  opened  wider.  The  engine  should  be  worked  up  to 
speed  gradually  so  that  proper  attention  can  be  given  to  the 
regulation  of  the  injection  water  as  the  steam  flowing  into  the 
condenser  gradually  increases. 

When  the  engine  is  up  to  speed  and  before  the  load  is  thrown 
on  it  is  a  good  plan  to  go  to  the  end  of  the  condenser  discharge 
pipe  and  find  out  how  hot  the  water  is.  This  may  be  done  with 
the  hand.  The  water  should  be  decidedly  cooler  than  the  hand, 
but  if  not,  more  injection  water  must  enter  the  condenser. 
When  the  load  is  thrown  on,  it  is  a  safe  plan  to  again  test  the  dis- 
charge water  and  if  the  condenser  is  working  properly  it  will  now 
be  perceptibly  warmer  than  the  hand.  It  may  be  about  as  warm 
as  a  person  would  ordinarily  heat  water  for  washing  the  hands. 


HANDBOOK    ON    ENGINEERING.  259 

When  the  discharge  becomes'  so  hot  as  to  be  unbearable  to  the 
bandit  is  a  sign  of  impending  danger,  viz.,  that  of  losing  the 
vacuum. 

It  is  a  good  plan  to  have  a  small  auxiliary  injection  pipe  con- 
nected to  the  city  mains  or  to  the  delivery  pipe  of  any  cold 
water  pump,  which  can  be  used  to  supplement  the  main  injection 
in  emergencies  of  this  kind.  When  a  jet  condenser  lifts  its  own 
water,  it  must  lose  the  suction,  as  it  is  called,  whenever  it  loses 
the  vacuum,  so  that  without  the  aid  of  the  auxiliary  injection 
pipe  it  can  seldom  regain  the  vacuum  without  allowing  the 
engine  to  exhaust  into  the  atmosphere  until  the  condenser  can  be 
cooled.  When  xhe  load  suddenly  increases  and  the  discharge 
becomes  too  hot,  the  normal  temperature  can  generally  be  quickly 
restored  by  opening  the  auxiliary  injection  valve.  The  auxiliary 
injection  is  generally  provided  on  condensers.  It  may  enter 
anywhere  in  the  exhaust  pipe.  An  auxiliary  injection  can  be 
made  of  a  piece  of  1£  or  2-inch  pipe  about  3  feet  long,  per- 
forated with  small  holes  so  as  to  make  a  sprayer  head,  the  sprayer 
head  being  connected  with  the  same  sized  pipe  from  the  city  main 
or  pump.  The  auxiliary  injection  is  in  every  sense  an  emergency 
apparatus  and  should  be  carefully  watched  while  in  operation, 
and  shut  off  as  soon  as  the  need  of  it  ceases  because  it  is  not 
automatic  and  if  allowed  to  run  unnoticed  there  is  danger  of 
flooding  the  condenser  and  exhaust  pipe  and  of  working  water 
back  to  the  engine.  When  the  load  on  the  engine  is  fairly  steady, 
or  when  the  load  fluctuates  uniformly  between  certain  limits  the 
condensing  apparatus  will  require  very  little  attention.  The  same 
precautions  should  be  taken  with  a  condenser  that  raises  its  own 
water  as  with  a  boiler  feed  pump,  viz.,  to  see  that  nothing  inter- 
feres with  its  continued  operation,  that  the  suction  pipe  is  properly 
protected  so  that  no  obstruction  may  enter  and  that  the  discharge 
is  always  free. 

It  is  sometimes  necessary  to  change  from  noncondensing  to 
condensing  without  stopping  the  engine.  In  this  case  the  gate 


260  HANDBOOK    ON    ENGINEERING. 

valve  in  the  exhaust  pipe  leading  to  the  condenser  will  be  found 
closed  because  this  valve  should  always  be  closed  when  the  con- 
denser is  not  in  use,  otherwise  the  steam  would  be  apt  to  injure 
the  valves  in  the  condenser.  The  air  pump  is  first  started  and 
the  injection  valve  opened  in  the  same  manner  as  when  about  to 
start  the  engine,  and  is  opened  to  the  running  position  with  a 
load.  When  the  condenser  is  working  properly  an  assistant 
should  be  stationed  at  the  back  pressure  valve  ready  to  close  it 
when  signaled  by  the  engineer.  The  gate  valve  in  the  exhaust 
pipe  is  then  partly  opened,  the  engineer  watching  the  vacuum 
gauge  to  note  the  point  at  which  the  vacuum  begins  to  drop.  At 
that  moment  he  signals  the  assistant,  who  then  closes  the  back 
pressure  valve.  The  gate  valve  is  then  opened  wide.  When 
opening  the  gate  valve,  and  before  the  back  pressure  valve  is 
closed,  care  must  be  taken  not  to  continue  to  open  the  valve  after 
the  vacuum  begins  to  fall,  otherwise  the  vacuum  will  be  quickly 
lost  entirely. 

When  changing  from  condensing  to  noncondensing  all  that  is 
necessary  is  to  close  the  gate  valve  in  the  exhaust  pipe  and  stop 
the  condenser.  As  soon  as  the  pressure  in  the  exhaust  pipe 
equals  that  of  the  atmosphere,  the  back  pressure  valve  opens 
automatically. 

The  surface  condenser  is  worked  in  the  same  manner  as  the  jet 
condenser,  which  has  just  been  described.  There  is  an  extra 
pump,  which  must  keep  the  circulating  water  flowing  through  the 
condenser  tubes ;  that  much  work  being  taken  off  the  air  pump. 
The  air  pump  has  air  and  some  water  to  handle  in  the  same 
manner  as  though  it  pumped  the  cooling  water.  Both  these 
pumps,  together  with  the  pump  of  the  jet  condenser,  require  the 
same  care  and  attention  that  the  boiler  feed  pump  does  or  any 
pump  that  lifts  water  by  suction. 

When  stopping  a  condensing  engine,  stop  the  engine  first,  then 
the  condenser,  then  shut  off  the  oil  cups  and  lubricators  and 
lastly  open  the  drips. 


HANDBOOK   ON   ENGINEERING. 


261 


SETTING  THE  PISTON  TYPE  OF  VALVE. 

The  simple  piston  valve  admitting  steam  between  the  pistons 
is,  in  operation,  the  reverse  of  the  plain  D  slide  valve,  which  ad- 
mits steam  at  the  outer  edges,  or  ends  of  the  valve.  To  make 
this  still  clearer  it  may  be  said  that  were  the  live  steam  to  enter 
through  the  exhaust  cavity  of  the  D  slide  valve  its  operation  and 
the  position  of  the  eccentric  relative  to  the  crank  would  be  iden- 


WMMWr/////J^<. 

Fig.  160.    Similarity  between  the  slide  and  piston  valves. 

tical  to  the  piston  valve.     Fig.  160     illustrates  the  similarity  of 
action  and  eccentric  positions  were  these  conditions  to  obtain. 

In  these  types  of  valve,  as  ordinarily  employed,  the  steam  is 
admitted  at  the  ends  of  the  slide  valve,  and  between  the  pistons 
or  at  the  middle  of  the  piston  valve.  The  change  from  the  end 
to  the  middle  of  the  valve  necessitates  a  change  in  the  position 
of  the  eccentric  relative  to  the  crank  in  order  to  have  the  direc- 
tion of  rotation  remain  the  same.  The  positions  of  the  eccentric 
when  driving  the  simple  D  valve,  and  the  piston  valve,  are  indi- 


262 


HANDBOOK    ON    ENGINEERING. 


cated  in  Fig.  161.  It  will  be  noticed  that  the  crank  revolves  in  the 
same  direction  in  both  cases,  and  that  when  the  crank  leaves  the 
dead  center,  moving  in  the  direction  of  the  arrow,  the  same  port, 
viz.,  the  one  at  the  head  end  of  the  cylinder,  will  be  opened  at  the 
same  time  and  to  the  same  extent.  This  proves  the  positions  as( 
shown  to  be  correct  and  illustrates  why  the  eccentric  must  be 
moved  in  the  same  direction  the  engine  is  to  run  with  the  D  valve, 
and  in  the  opposite  direction  with  the  piston  valve,  in  order  to 
secure  the  same  direction  of  rotation  in  the  engine. 


f 


Fig*  161*  •  Valves  opening:  the  ports  for  admission. 

When  setting  valves  it  is  a  good  plan  to  obtain  as  much  uni- 
formity of  methods  as  possible,  because  of  the  liability  to  con- 
fusion when  methods  involving  different  movements  of  the 
eccentric  are  employed.  In  all  the  directions  that  follow  it  is 
assumed  that  the  crank  is  placed  on  the  dead  center  (sae  page 
195)  nearest  the  cylinder  so  that  when  setting  the  different  styles 
of  valves,  the  same  steam  port  will  always  be  opened  first,  namely, 
the  one  at  the  head  end  of  the  cylinder.  The  engine,  it  will  be 


HANDBOOK    ON   ENGINEERING. 


263 


seen,  'is  thus  treated  as  though  it  contained  but  one  steam  port, 
which  greatly  simplifies  matters. 

In  order  to  show  that  each  particular  form  of  valve  of  the  same 
type  does  not  require  different  methods  for  its  proper  adjustment, 
both  the  simple  piston  valve  and  the  main  valve  of  the  round  riding 
cut-off  are  illustrated  together,  the  same  directions  applying  to 
both. 

Where  marks  appear  upon  the  valve  stem,  or  seat,  it  becomes 
an  easy  matter  to  set  a  valve  quickly  and  correctly  but  when  these 
do  not  appear  a  different  method  must  be  pursued  for  obtaining 
them.  First  remove  the  chest  covers  at  both  ends  of  the  chest 


Fig.  162.    Templates  used  in  setting  piston  valves. 

and  also  the  valve  (both  styles)  from  the  chest  and  lay  it  upon  a 
clean  place  on  the  floor,  or  bench.  Procure  a  piece  of  sheet  steel 
about  T\  inch  thick  and  file  it  to  the  form  shown  in  Fig.  162. 
Make  the  length  of  the  gauge  thus  formed  equal  to  the  thickness 
of  the  piston  on  the  valve  plus  the  lead,  which  may  betaken  as  ^ 
inch.  Replace  the  valve  in  the  chest  and  connect  it  to  the  valve 
stem.  Turn  the  eccentric  from  one  extreme  position  to  the  other 
and  see  that  the  valve  opens  the  ports  an  equal  amount.  It  is  not 
necessary  that  the  ports  be  opened  exactly  wide,  the  object  being 
to  secure  exactly  the  same  opening  at  each  end  of  the  valve.  If 
the  head  end  port  is  opened  farther  than  the  other,  the  eccentric 


264  HANDBOOK   ON   ENGINEERING. 

rod  should  be  lengthened  an  amount  equal  to  one-half  the  differ- 
ence, and  should  the  port  at  the  crank  end  be  opened  farthest, 
the  eccentric  rod  should  be  shortened  a  like  amount. 

Turn  the  eccentric  to  the  extreme  position  farthest  from  the 
cylinder.  Then  place  the  small  end  of  the  gauge  against  the  inner 
edge  of  the  port,  and  with  a  scriber  make  a  fine  line  (a)  on  the 
seat  as  shown  in  Fig.  163.  Remove  the  gauge,  and  turn  the  eccen- 
tric in  the  same  direction  the  engine  is  to  run  until  the  end  of  the 
valve  reaches  the  fine  line  on  the  seat.  Secure  the  eccentric  to 
the  shaft,  being  careful  not  to  move  the  eccentric  in  either  direc- 
tion. Now  turn  the  crank  in  the  direction  it  is  to  run  until  the 
eccentric  reaches  the  extreme  position  nearest  the  cylinder.  The 
gauge  is  now  placed  against  the  edge  of  the  opposite  port  and  a 


Fig.  163.    Showing  the  use  of  the  template. 

fine  line  drawn  on  the  seat,  at  the  end  of  the  gauge,  in  the  same 
manner  as  shown  in  Fig.  163.  Turn  the  crank  to  the  dead  center 
farthest  from  the  cylinder  when  the  end  of  the  valve  should  have 
just  reached  the  line  on  the  seat.  If  it  does  not,  the  crank 
should  be  turned  sufficiently  to  enable  the  distance  between  the 
valve  and  the  mark,  being  measured.  The  eccentric  rod  is  then 
to  be  adjusted  so  as  to  move  the  valve  a  distance  equal  to  one- 
half  of  what  the  valve  lacks  of  exactly  reaching  the  line  on  the 
seat.  The  valve  will  then  open  both  ports  to  the  extent  of  the 

16 


HANDBOOK   ON   ENGINEERING.  265 

lead  when  the  crank  occupies  the  exact  dead  centers.  It  is  very 
desirable  to  have  a  method  of  setting  the  valve  without  removing 
the  chest  covers.  By  the  aid  of  simple  gauges  this  can  be  readily 
accomplished.  Take  a  piece  of  steel  wire  and  sharpen  the 
ends  and  bend  into  the  form  shown  in  Fig.  164.  With  a  prick 
punch  make  a  mark  (&)  on  the  guide  block,  place  one  end  of 
gauge  in  this  mark  and  make  another  mark  (c)  where  the  opposite 
end  of  the  gauge  touches  the  valve  stem.  This  gauge  enables 
the  valve  stem  being  disconnected  from  the  valve  stem  guide 
block,  and  the  chest  cover  put  on,  and  the  stem  afterward  con- 
nected up  again  in  exactly  the  same  position  (see  page  243). 
Having  made  this  second  gauge,  place  the  crank  on  the  exact 
dead  center  nearest  the  cylinder.  Then  make  a  prick  punch  mark 
(d)  on  the  stuffing-box,  place  one  end  of  the  gauge  in  this  mark 
and  then  make  a  second  mark  (e)  where  the  other  end  of  the 
gauge  touches  the  valve  stem.  It  will  readily  be  seen  that  when 
testing  the  setting  of  the  valve  all  that  is  necessary  is  to  place 
the  crank  on  the  dead  center  nearest  the  cylinder,  then  place  the 
gauge  in  the  mark  (d)  on  the  stuffing-box,  and  have  the  eccentric 
moved  until  the  punch  mark  (e)  on  the  valve  stem  falls  under 
the  point  of  the  gauge.  The  valve  will  then  have  opened 
the  port  to  the  extent  of  the  lead,  because  it  was  in 
this  position  when  the  gauge  and  the  marks  were  first 
made.  If  the  punch  marks  are  nicely  made  and  not  too  large 
the  extent  of  the  lead  opening  may  be  measured  at  both  ports, 
by  turning  the  crank  to  the  opposite  dead  center  and  making  a 
second  punch  mark  (/)  on  the  valve  stem  by  means  of  the  gauge. 
These  two  guages  should  be  carefully  preserved  from  injury  and 
from  being  mislaid  so  that  in  case  of  emergency,  such  as  the 
slipping  of  an  eccentric,  the  latter  can  be  returned  to  its  correct 
position  without  unnecessary  loss  of  time. 


266 


HANDBOOK   ON   ENGINEERING. 


SETTING  THE  CUT=OFF  VALVE. 

The  following  directions  are  applicable  to  both  the  flat  slide 
and  the  round  types  of  slide  valves. 

The  point  of  latest  cut-off  is  seldom  known  exactly  by  the 
average  engineer  because  of  its  unimportance  while  the  engine  is 
in  running  order,  and  as  this  point  varies  with  different  engines 
it  is  advisable  to  discard  it  as  an  element  in  valve  setting.  First 
place  the  main  valve  in  its  position  of  mid -travel,  that  is,  place 
it  centrally  over  the  ports.  This  may  be  accomplished  by  finding 
the  center  between  the  punch  marks  (/)  and  (e)  on  the  valve 
stem,  bringing  the  center  mark  g  under  the  point  of  the  gauge  in 
the  manner  shownin  Fig.  164.  The  travel  of  thecut-off  valve  must 
first  be  equalized  which  is  accomplished  by  turning  the  cut-off 


Fig.  164.    Trams  for  setting  the  cut-off  valve. 


eccentric  to  its  extreme  positions  and  noting  the  travel  of  the 
cut-off  valve  over  the  ports  of  the  main  valve.  The  cut-off  eccen- 
tric rod  should  be  lengthened  or  shortened  so  that  the  cut-off 
valve  will  travel  evenly  over  the  ports  in  the  main  valve.  This, 
of  course,  is  obtained  by  measuring  the  distance  from  the  edge 
of  the  ports  in  the  main  valve  to  the  ends  of  the  cut-off  valve  when 
the  latter  occupies  its  extreme  positions. 

First,  assume  the  engine  to  have  a  fixed,  or  a  hand-adjusted 
cut-off,  and  that  the  cut-off  valve  is  to  be  set  to  cut  off  steam  at 


HANDBOOK   ON   ENGINEERING. 


267 


one-half  stroke.  Place  the  crank  on  the  dead  center  (see  page 
195)  and  the  full  part  of  the  cut-off  eccentric  the  same.  Then 
measure  off  one-half  the  length  of  the  stroke  from  the  end  of  the 
cross-head  as  in  Fig.  165  and  make  a  light  line/ on  the  guide.  Turn 
the  engine  in  the  direction  it  is  to  run  until  the  end  of  cross-head 


Fig.  165.    Method  of  equalizing  the  cut-off. 

reaches  the  line  /  on  the  guide.  The  piston  will  now  have  com- 
pleted one-half  its  stroke.  Turn  the  cut-off  eccentric  in  the 
direction  the  engine  is  to  run  until  the  cut-off  valve  opens  the 
port  in  the  main  valve  wide  and  just  closes  the  port  again  in  the 
main  valve. 

Secure  the  cut-off  eccentric  to  the  shaft  at  this  point. 
Turn  the  crank  over  to  the  opposite  dead  center  and  far  enough 
beyond  the  center  so  that  the  same  end  of  the  crosshead  will  have 
again  reached  the  line  (/)  on  the  guide  as  in  Fig.  165.  The  piston 
will  now  have  completed  one-half  of  the  return  stroke  and  the 
cut-off  valve  should  have  just  closed  the  port  in  the  main  valve. 
If  the  cut-off  valve  has  moved  too  far,  or  notfar  enough,  measure 
the  amount  it  lacks  of  just  closing  the  port  and  then  adjust  the 
cut-off  eccentric  rod  an  amount  equal  to  one-half  the  amount  of 


268  HANDBOOK   ON   ENGINEERING. 

the  discrepancy.  The  cut-off  valve  will  then  close  the  port  in  the 
main  valve  at  exactly  the  same  point  in  both  forward  and  return 
strokes. 

When  an  automatic  cut-off  engine,  in  which  the  cut-off 
eccentric  is  operated  by  a  shaft  governor,  first  block  out  the 
weights  to  their  extreme  position  or  against  the  stops,  the  travel 
of  the  cut-off  valve  having  been  previously  equalized  in  the 
manner  explained  above.  Then  turn  the  crank  to  the  dead  center, 
preferably  the  one  nearest  the  cylinder,  and  turn  the  full  part  of 
the  cut-off  eccentric  to  the  same  position  as  a  starting  point. 
Then  turn  the  eccentric  in  the  direction  the  engine  is  to  run  until 
the  cut-off  valve  opens  the  port  in  the  main  valve  to  the  extent  of 
the  lead  or  from  ^  to  -^  inch.  Secure  the  governor  wheel  to 
the  shaft  at  this  point.  Turn  the  crank  to  the  opposite  dead 
center  and  see  that  the  cut-off  valve  has  opened  the  port  in  the 
main  valve  to  the  same  extent ,  If  it  hac  not  done  so,  adjust  the 
length  of  the  eccentric  rod  an  amount  equal  to  one-half  the  differ- 
ence between  the  two  lead  openings.  Take  out  the  blocks  and 
the  work  will  be  completed.  It  will  readily  be  understood  that, 
were  the  speed  of  the  engine  to  reach  a  point,  where  the 
governor  weights  strike  the  stops,  the  cut-off  valve  will  admit 
only  steam  enough  to  fill  the  clearance,  which  should  always  be 
done,  because  while  it  does  not  tend  to  accelerate  the  speed  it 
does  prevent  forming  a  vacuum  in  the  cylinder,  and  from  drawing 
in  whatever  may  happen  to  be  in  the  vicinity  of  the  end  of  the 
exhaust  pipe.  The  point  of  latest  cut-off  will  then  take  care  of 
itself  and  will  occur  at  that  point  for  which  the  valve  and  gear 
were  designed. 

FLAT  VALVE  RIDING  CUT-OFF. 

In  medium  and  slow  speed  engines  it  is  very  desirable  to  have 
a  uniform  point  of  release  and  constant  compression.  If  the 
engine  is  of  the  automatic  cut-off  variety  the  point  of  cut-off  will 


HANDBOOK   ON   ENGINEERING.  269 

necessarily  change  with  each  change  of  load,  and  if  the  steam  is 
released,  and  the  point  of  compression  determined  by  the  valve 
effecting  the  cut-off,  it  is  plain  that  as  the  cut-off  varies,  the  point 
of  exhaust  and  of  compression  must  also  vary  proportionately. 
In  order  to  secure  a  uniform  amount  of  lead,  a  constant  point  of 
release  and  of  compression,  it  is  necessary  that  the  valve  deter- 
mining these  points  be  given  a  constant  travel.  Then  in  order  to 
produce  a  variable  cut-off  a  separate  cut-off  valve  must  be  pro- 
vided. This  is  the  object  of  the  riding  cut-off.  The  main  valve 
determines  the  lead,  point  of  release  and  point  of  exhaust  closure 
and  as  the  travel  of  the  main  valve  relative  to  the  crank  is  un- 
changeable these  functions  always  remain  the  same.  The  duty  of 
the  cut-off  valve  is  simply  to  close  the  ports  in  the  main  valve, 
and  it  determines  the  point  of  cut-off  only.  It  will  be  seen,  there- 
fore, that  with  this  arrangement  of  valves,  constant  lead,  exhaust 


Fig.  166.    Riding  cut-off  —  Showing  yalyes  and  eccentrics. 

opening  and  constant  compression  are  secured  while  the  point  of 
cut-off  is  constantly  changing  with  the  load.  Keeping  these  fun- 
damental facts  in  mind,  it  is  readily  seen  that  the  main  valve  of 
the  riding  cut-off  is,  in  operation,  exactly  the  same  as  the  ordi- 
nary D  slide  valve  having  a  fixed  travel.  In  the  riding  cut-off 
the  travel  of  the  cut-off  valve  is  fixed,  so  far  as  length  of  stroke 
is  concerned,  but  the  times  of  closing  the  ports  in  the  main  valve 
are  variable  and  are  determined  either  by  hand  adjustment  or  by 
the  governor,  depending  upon  whether  the  engine  is  a  throttling 
or  an  automatic  cut-off  engine.  The  points  of  cut-off  are 
changed  by  rolling  the  cut-off  eccentric  around  on  the  shaft. 


270 


HANDBOOK    ON    ENGINEERING. 


The  farther  the  cut-off  eccentric  is  set  in  advance  of 
the  crank  the  earlier  in  the  stroke  will  steam  be  cut  off, 
and,  the  nearer  together  the  two  eccentrics  are  set,  the  later 
will  the  cut-off  occur.  The  main  valve  is  generally  designed 
to  cut  off  steam  at  f  or  J  stroke,  so  that  if  the  cut- 
off valve  and  main  valve  move  together  the  point  of  cut-off 
will  be  determined  by  the  main  valve  and  will  occur  at  f  or 
|  stroke.  Now  if  the  cut-off  eccentric  (c)  be  set  ahead  of 
the  main  eccentric  (m)  as  in  Fig.  166,  it  will  reach  the  end  of  its 
stroke  and  start  back  again  before  the  main  eccentric  has  com- 
pleted the  stroke,  thus  the  cut-off  valve  moves  in  one  direction 
and  the  main  valve  in  the  opposite  direction  and  that  point  in  the 
piston  stroke  at  which  the  centers  of  the  two  valves  meet  will  be 
the  point  of  cut-off.  If  the  cut-off  eccentric  be  set  nearly  oppo- 
site the  main  eccentric  it  is  evident  that  when  the  main  valve 
reaches  one-half  of  the  outward  stroke  the  cut-off  valve  will  have 
reached  nearly  one-half  of  the  return  stroke  and  the  cut-off  will 
occur  at  about  this  point  in  the  piston  stroke,  which  will  be 
approximately  one-fourth  stroke. 


Fig.  167.    Setting  yalyes  of  the  riding  cut-off. 

When  setting  the  valves,  first  equalize  the  port  opening  of  the 
main  valve.  This  is  accomplished  by  turning  the  main  eccentric 
from  one  extreme  position  to  the  other  seeing  that  both  ports  in 
the  valve  seat  leading  into  the  cylinder  are  opened  exactly  the 
same  amount.  It  is  not  necessary  that  these  ports  be  opened 
exactly  wide ;  the  object  is  to  see  that  both  ports  are  opened  to 
the  same  extent  when  the  eccentric  is  in  its  extreme  positions. 


HANDBOOK   ON   ENGINEERING.  271 

Having  equalized  the  travel  of  the  main  valve  place  the  crank  on 
the  dead-center,  see  page  195,  and  turn  the  full  side  of  the  main 
eccentric  to  a  corresponding  position.  Then  turn  the  eccentric 
in  the  direction  the  engine  is  to  run  until  the  port  in  the  main 
valve,  corresponding  to  the  position  of  the  crank  or  piston,  opens 
the  port  leading  into  the  cylinder  to  the  amount  of  the  lead,  which 
may  be  taken  as  ^  inch.  Now,  before  moving  the  engine  make 
a  gauge  of  the  form  shown  in  Fig.  167.  Put  a  punch  mark  on  the 
stuffing-box,  and,  placing  one  end  of  the  gauge  in  this  mark,  draw  a 
fine  line  on  the  valve  stem  at  the  opposite  point  of  the  gauge. 
Turn  the  crank  to  the  opposite  dead-center  and  note  the  amount 
of  lead  opening.  If  it  is  not  the  same  as  first  obtained  adjust  the 
eccentric  rod  to  the  extent  of  one-half  the  difference.  Then  place 
the  gauge  in  the  punch  mark  on  the  stuffing-box  and  draw  a  fine 
line  at  the  opposite  point  of  the  gauge. 

Turn  the  crank  back  again  to  its  first  position  and  note  the 
lead.  If  it  is  found  to  be  equal  at  both  ends,  apply  the 
gauge  again  and  this  time  make  a  light  punch  mark  at  the  outer 
point  of  the  gauge.  Then  put  a  similar  punch  mark  on  the  fine 
line  representing  the  lead  at  the  opposite  end  of  the  valve  travel. 
By  means  of  these  marks  it  will  be  possible  to  set  the  main  valve 
correctly  without  removing  the  steam  chest  cover.  Now  divide 
the  distance  between  the  two  punch  marks  and  put  a  third  punch 
mark  at  the  middle.  Turn  the  crank  around  in  the  direction 
the  engine  is  to  run  until  the  middle  punch  mark  falls  under  the 
outer  point  of  the  gauge.  The  main  valve  will  now  be  at  the 
middle  of  its  travel.  The  travel  of  the  cut-off  valve  must  now  be 
equalized  so  that  the  latter  valve  will  travel  equal  distances  be- 
yond the  ports  in  the  main  valve.  This  is  accomplished  in  pre- 
cisely the  same  manner  as  with  the  main  valve.  Having 
equalized  the  travel  of  the  cut-off  valve,  turn  the  crank  in  the 
direction  the  engine  is  to  run  until  the  cross-head  reaches  the  point 
in  the  stroke  at  which  the  cut-off  is  to  occur,  which  is  to  be  de- 


272  HANDBOOK   ON   ENGINEERING. 

signated  by  a  line  drawn  on  the  guide.  Now  turn  the  cut-off 
eccentric  in  the  same  direction  until  it  reaches  its  extreme  position. 
Continue  to  move  the  eccentric  until  the  cut-off  valve  just  closes 
the  port  in  the  main  valve.  Secure  the  cut-off  eccentric  to  the 
shaft  at  this  point.  Then  turn  the  crank  around  until  the  cut- 
off takes  place  on  the  return  stroke  and  see  if  it  corresponds  to 
the  point  on  the  previous  stroke.  If  not,  adjust  the  length  of 
the  cut-off  eccentric  rod  an  amount  equal  to  one-half  the  differ- 
ence. 

It  is  important  to  be  able  to  set  the  cut-off  valve  also  without 
taking  off  the  steam  chest  cover.  One  punch  mark  only  is  re- 
quired for  this.  Place  the  main  valve  in  its  position  of  mid- 
travel  by  means  of  the  gauge.  Then  put  a  punch  mark  on  the 
stuffing-box  of  the  cut-off  valve  stem  and,  placing  the  gauge  in 
this  mark,  put  another  at  the  opposite  end  of  the  gauge  on  the 
cut-off  valve  stem.  See  Fig.  167. 

This  method  furnishes  a  simple  and  quick  means  of  setting 
both  the  main  and  cut-off  valves  when  an  eccentric  slips.  All 
that  is  necessary  is  to  place  the  crank  on  the  dead-center  and 
bring  the  proper  punch  mark  under  the  point  of  the  gauge.  Then 
bring  the  main  valve  to  its  position  of  mid-travel  and  with  the 
gauge  bring  the  cut-off  valve  to  its  proper  position. 

The  foregoing  directions  for  setting  the  cut-off  eccentric  apply 
to  the  hand-adjusted  gear  only.  When  the  cut-off  eccentric  is 
operated  by  the  governor,  the  travel  is  equalized  in  precisely 
the  same  manner  as  when  hand-adjusted.  After  equalizing  the 
travel  of  the  cut-off  valve,  place  the  crank  on  the  dead-center. 
The  main  valve,  which  is  invariably  set  first,  will  now  open  the 
port,  corresponding  to  the  position  of  the  piston  to  the  extent  of 
the  lead.  Next  block  out  the  governor  weights  against  the  stops. 
Turn  the  full  side  of  the  cut-off  eccentric  to  correspond  to  that  of 
the  crank  as  a  starting-point.  Then  turn  the  cut-off  eccentric 
(governor  wheel),  around  on  the  shaft  in  the  direction  the  engine 


HANDBOOK   ON    ENGINEERING.  273 

is  to  run  until  the  port  in  the  main  valve  is  opened  to  the  extent 
of  the  lead.  Secure  the  governor  wheel  to  the  shaft.  Turn  the 
crank  to  the  opposite  dead-center  and  see  that  the  cut-off  valve 
opens  the  port  in  the  main  valve  to  the  same  extent.  If  the 
difference  is  slight  it  may  be  equalized  by  adjusting  the  length 
of  the  cut-off  eccentric  rod  an  amount  equal  to  one-half  the  differ- 
ence of  the  lead  openings.  Should  the  difference  be  great,  say, 
one-half  inch,  that  is,  should  the  cut-off  valve  lack  one-half  inch 
of  opening  the  port  in  the  main  valve,  it  indicates  that  the  cut-off 
valve  is  too  long,  which  is  apt  to  be  the  case  where  two  cut-off 
valves  are  employed  on  the  same  stem.  The  valve  may  be 
shortened  by  moving  the  two  parts  closer  together,  moving  each 
part  one-fourth  of  the  amount  the  cut-off  valve  lacked  of  opening 
the  port  in  the  main  valve.  Then  begin  over  again  to  set  the 
cut-off  eccentric  and  if  the  adjustments  have  been  carefully  made 
it  will  open  the  ports  correctly  at  both  ends  of  the  main  valve. 
After  fastening  the  main  eccentric  and  the  governor  wheel  securely 
to  the  shaft  remove  the  blocks  from  the  governor  weights  and  the 
job  will  be  finished. 

When  the  valve  gear  contains  a  rocker-shaft  of  the  construc- 
tion shown  on  page  322,  the  eccentric  must  be  turned  in  the 
opposite  direction  to  that  in  which  the  engine  is  to  run,  until  the 
main  valve  opens  the  port  leading  into  the  cylinder,  to  the  extent 
of  the  lead. 


To  Find  Arerage  Length  of  Stroke  of  Piston. 

Revs,  per  Mln. 

25  to  90        Dlam.  of  cyl.  X  2.5    =  Length  of  stroke  In  inches. 

90  "  176  "  "      x  2      =        " 

175  "  300  "  "X  1.33=        "  "  " 

Single  Acting,  "  "      x  1       =        " 

Weight  of  Engines  per  Cubic  Foot  Cyl.  Volume. 

Girder  Frame.  Box  Frame. 

Lowspeed 4800Lbs.  4400  Lbs. 

Highspeed 6000    "  4800    *« 

Cross  compound  non -condensing 8600    " 

Cross  compound  condensing  9300    | 

Tandem  compound  condensing  8650 

Tandem  compound  non-condensing  °°7d 


274  HANDBOOK    ON    ENGINEERING. 


CHAPTER     XII. 
THE  STEAM  ENGINE.  —  CONTINUED. 

Work  consists  of  the  sustained  exertion  of  force  through  space. 
The  unit  of  work,  the  foot-pound,  is  a  force'  of  one  pound  exerted 
through  one  foot  space.  The  work  done  in  lifting  one  pound  ten 
feet,  or  ten  pounds  one  foot,  is  ten  foot-pounds. 

Power  is  the  rate  of  work,  or  the  number  of  foot-pounds  ex- 
erted in  a  unit  of  time.  The  unit  of  power  is  the  horse-power, 
and  equals  33,000  foot-pounds  exerted  in  a  minute,  or  550  foot- 
pounds exerted  in  a  second,  or  1,980,000  foot-pounds  exerted  in 
an  hour.  An  engine  developing  fifty  horse-power,  exerts  27,500 
foot-pounds  per  second,  1,650,000  foot-pounds  in  a  minute.  It 
could  raise  (friction  neglected)  41,250  pounds  forty  feet  in  one 
minute. 

A  belt  running  over  a  .pulley  at  4,000  feet  per  minute,  pulling 
with  a  force  of  240  pounds  (fair  load  for  a  4-inch  belt)  will 
transmit 

240x4.000 

—  OQ  QQQ  —  equal  thirty  horse-power  (nearly). 


If  moving  at  1,100  feet  pe'r  minute,  the  result  would  be 

240x1,100 

•  —  QQ  QQQ  —  *equa~l  eight  horse-power. 

A  gear-wheel,  the  cogs  of  which  transmit  a  pressure  of  1,800 
pounds  (fair  load  for  1J"  pitch  6"  face)  to  the  cogs  of  its  mate, 
the  periphery  velocity  of  the  wheels  being  ten  feet  per  second, 
transmits 

1,800x10 

equal  thirty-three  horse-power  nearly. 


HANDBOOK    ON    ENGINEERING.  275 

If  speed  was  360  feet  per  minute,  it  would  transmit 

1,800x360 

— QQ  QQQ —  equal  twenty  horse-power  nearly. 

The  horse-power  developed  by  a  steam  engine  consists  of  two 
primary  factors,  Piston  Speed  and  Total  Average  Pressure  of 
steam  upon  the  piston. 

Piston  speed  depends  upon  the  stroke  of  engine  and  the  num- 
ber of  revolutions  per  minute.  An  engine  with  stroke  of  twelve 
inches,  making  300  revolutions  per  minute,  has  a  piston  speed  of 

2  x  12  x  300 

— r-^-; equal  600  feet  per  minute. 

La 

Piston  speed  of  an  engine  with  24"  stroke  at  150  revolutions 
per  minute : 

2x24x150 

T^- equal  600  feet  per  minute. 

L4 

Total  average  pressure  depends  on  area  of  piston  and  mean 
effective  pressure  per  square  inch  exerted  on  piston  throughout 
stroke.  The  mean  effective  pressure  (M.  E.  P.)  in  any  case  can 
only  be  accurately  obtained  by  means  of  the  steam  engine  indi- 
cator, and  depends  upon  the  load  engine  is  carrying. 


GENERAL  PROPORTIONS. 

Diameter  of  steam  pipes : 

Slide-valve  engine,   J    diameter   of    piston. 
Automatic  high-speed  engines,  |  diameter  of  piston. 
Corliss  engine,  T3^  diameter  of  piston. 

Diameter  of  exhaust  pipes : 

Slide-valve  engine,  |  diameter  of  piston. 
Automatic  high-speed  engine,  f  diameter  of  piston. 
Corliss  engine,  f  to  f  diameter  of  piston. 


276  HANDBOOK    ON    ENGINEERING. 

Displacement  of  piston 

Clearance  spaces :  in  °ne  stroke. 

Slide-valve  engine 0.06  to  0.08 

Automatic  high-speed  engine,  single  valve       .  0.08  to  0.15 

Automatic  high-speed  engine,  double  valve      .  0.03  to  0.05 
Automatic  cut-off  engine,  Corliss  type,  long 

stroke 0.02  to  0.04 

Weights  of  engines  per  rated  horse-power : 

Slide-valve  engine 125  to  135  Ibs. 

Automatic  high-speed  engine        90  to  120  Ibs. 

Corliss  engine 220  to  250  Ibs. 

Fly-wheels,  weight  per  rated  horse-power : 

Slide-valve  engine 33  Ibs. 

Automatic  high-speed  engine 25  to  33  Ibs. 

(According  to  size  and  speed.) 
Corliss  engine 80  to  120  Ibs. 

(According  to  size  and  speed.) 

RULES  FOR  FLY-WHEEL  WEIGHTS,  SINGLE  CYLINDER 
ENGINES. 

Let  d  =  diameter  of  cylinder  in  inches. 
S  =  stroke  of  piston. 
D  =  diameter  of  fly-wheel  in  feet. 
R  =  revolutions  per  minute. 
W  =  weight  of  fly-wheel  in  pounds. 

d2  S 
For  slide-valve  engines,  ordinary  duty    .      W=  350,000  jyTlp 

d*  S 
For  slide-valve  engines,  electric  lighting.      W=  700,000  ^  ^ 

d?  S 
For  automatic  high-speed  engines     .     .      W=  1,000,000  ™  j* 


HANDBOOK    ON    ENGINEERING. 

For  Corliss  engines,  ordinary  duty    .     .      W=  700,000 


277 
d*  S 


U*  IP 

d*  8 


For  Corliss  engines,  electric  lighting       .      W  =  1,000,000  -™ — 


Fig.  168.    The  Russell  engine. 

- 

SETTING  THE  VALVE  ON  A  RUSSELL  ENGINE,  SINGLE  VALVE 
TYPE.  THE  SAHE  PRINCIPLE  LAID  DOWN  IN  THE  SET- 
TING OF  THE  COHMON  SLIDE  VALVE  MUST  BE  ADHERED 
TO. 

The  style  of  valve  is  shown  in  cut,  Fig.  169.  It  is,  to  some 
extent,  a  moving  steam  chest  with  the  steam  all  within  itself , 
admitting  only  enough  steam  into  the  chest  to  keep  the  valve  to 
its  seat,  against  the  maximum  tendency  to  leave  it.  This  pres- 
sure in  the  chest  is  found  with  the  valve  as  at  present  propor- 
tioned, to  be  about  45  per  cent  of  that  contained  within  the 
valve.  The  cut  shows  the  valve  and  section  of  cylinder  so 
plainly  as  to  render  any  detailed  explanation  of  same  almost 
unnecessary. 


278 


HANDBOOK    ON    ENGINEERING. 


The  eccentric  operating  the  valve  is  under  control  of  the  gover- 
nor, as  shown  in  cut  Fig.  170,  which  regulates  the  speed  of  the 
engine  by  sliding  the  eccentric  across  the  shaft,  either  forward  or 
backward,  as  the  weights  change  their  position,  thereby  cutting 
the  steam  off  earlier  or  later  in  the  stroke,  as  the  governor,  or 
more  properly,  the  weights  adjust  themselves  to  the  load. 

When  the  eccentric  is  moved  across  the  shaft  in  a  direction 
that  reduces  its  'eccentricity,  the  steam  is  cut  off  earlier  in  the 


Fig.  169.    Sectional  view  of  Russell  steam  valve. 

stroke;  when  the  eccentric  is  moved  in  the  opposite  direction, 
the  steam  is  cut  off  later  in  the  stroke.  The  extreme  range  of 
this  cut-off  is  from  0  to  |  of  the  engine's  stroke,  and  this 
whole  range  of  adjustment  is  under  complete  control  of  the 
governor. 

To  preserve  &  certain  determined  speed  with  the  smallest  pos- 
sible variation,  as  changes  occur  in  the  load  or  pressure,  is  the 
function  of  the  governor.  The  cut-off  must  always  be  propor- 
tioned to  the  load.  When  the  engine  is  running  empty,  the  steam 
is  cut  off  at  the  beginning  of  the  stroke  and  the  governor  weights 
are  at  their  extreme  outer  position.  With  a  heavy  load,  steam 
follows  farther  and  the  weights  are  nearer  their  inner  position .  Be- 

16 


HANDBOOK    ON   ENGINEERING. 


279 


tween  these  two  limits,  any  number  of  positions  of  the  weights,  and 
corresponding  angular  positions  of  the  eccentric,  may  be  had ;  and 


Fig.  170.    The  Russell  shaft  governor. 

as  the  steam  is  thus  adapted  to  the  load  in  each  position,  it  follows 
that  a  slight  increase  or  decrease  in  speed  must  make  a  change  in 
the  cut-off  and  bring  the  engine  again  to  standard  speed. 


280  HANDBOOK    ON    ENGINEERING. 

In  setting  the  valves  it  is  necessary  to  mark  the  ports  in  the 
valve  face  at  the  outer  edge  of  the  steam  chest,  and  also  to  mark 
on  the  back  of  the  valve  the  ports  in  its  face,  so  that  it  may  be 
adjusted  after  being  placed  in  the  chest,  in  which  position  it  pre- 
sents a  blank  surface  that,  without  these  marks,  would  afford  no 
means  for  knowing  its  position. 

In  placing  the  valve  in  the  chest,  see  that  it  fits  perfectly 
against  the  seat  and  that  the  bottom  bearing,  on  which  the  valve 
rides,  is  at  right  angles  to  the  valve  seat,  and  in  such  a  condition 
that  the  valve  will  not  be  tipped  away  from  its  seat,  but  rather 
against  it.  This  latter  condition  will  be  insured  by  easing  off 
the  bottom  strip  at  the  inner  corner,  so  that  the  valve  would 
bear  hardest  at  the  outer  edge.  The  hinge  nut,  into  which  the 
valve  stem  is  screwed,  as  well  as  its  trunnion  bearings,  should 
fit  so  that  the  valve  lays  closely  to  its  seat,  rather  than  be  held 
away  from  it. 

Having  extended  the  marks  of  the  ports  as  well  in  the  valve 
seats  as  in  the  valve  itself,  to  the  outside,  it  now  becomes  neces- 
sary to  get  the  center  of  the  travel  of  the  eccentric  and  connect 
the  valve  and  rody  so  that  the  valve  will  travel  equally  on  either 
side  of  this  center.  The  throw  of  the  eccentric  leads  the  crank  in 
the  direction  the  engine  runs,  and  with  the  eccentric  properly 
located,  as  it  cannot  help  being,  because  .it  is  attached  to  the 
governor  and  the  governor  is  keyed  to  the  shaft,  the  lead  will 
remain  the  same  with  the  governor  weights  in  their  outer  as  well 
as  in  their  inner  positions. 

These  valves  are  usually  marked  with  the  engine  on  the  center 
at  either  end,  marks  corresponding  with  the  admission  edges  of 
valve  and  seat.  The  hinge  nut  connection  makes  it  convenient  to 
examine  these  valves  without  disconnecting  or  disturbing  any 
adjustments  made.  The  valve  rod  has  right  and  left-hand  threads 
for  adjustment,  and  final  adjustment  can  be  made  without  taking 
off  the  steam  chest  cover. 

17 


HANDBOOK   ON   ENGINEERING. 


281 


1 


a 


282 


HANDBOOK    ON    ENGINEERING. 


Fig.  172.    Governor  connections  —  Porter- Allen  engine. 


THE  ADJUSTABLE  PRESSURE  PLATES. 

Description  of  these  plates*  —  The  construction  of  these  pres- 
Mire  plates  and  the  method  of  ad  justing  them  are  fully  represented 
jathe  sections  of  the  cylinder,  Figs.  173  and  174. 

On  the  lowei4  side  of  the  horizontal  section  Fig.  173,  both 
admission  valves  are  shown,  working  between  their  opposite 
parallel  seats,  one  of  which  is  formed  on  the  cylinder,  and  the 
other  on  the  pressure  plates,  the  latter  having  cavities  opposite 
the  ports. 

The  valve  at  the  farther  end  of  the  cylinder  is  at  the 
extremity  of  its  lap,  while  the  one  at  the  crank  end  has  com- 
menced to  open  the  four  passages  for  admission  of  the  steam. 


HANDBOOK    ON    ENGINEERING. 


283 


The  vertical  cross-section,  Fig.  174, passes  through  the  middle 
of  one  pressure  plate  and  shows  its  form  and  the  means 
employed  for  its  adjustment.  It  is  made  hollow  and  most  of 


Fig.  173.    Cylinder  and  yalves  —  Porter- Allen  engine. 

the  steam  supplied  to  two  of  the  openings  passes  through  it. 
It  is  arched  to  resist  the  pressure  of  the  steam  without  deflec- 
tion. It  rests  on  two  inclined  supports,  one  above  and  the 
other  below  the  valve.  These  inclines  are  steep,  so  that  the 
plate  will  be  sure  to  move  freely  down  them  under  the  steam 
pressure,  and  also  that  it  may  be  closed  up  to  the  valve  with 
only  a  small  vertical  movement.  It  is  prevented  from  moving 
down  these  inclines  by  a  screw,  passing  through  the  bottom 
of  the  chest,  the  point  of  which,  as  also  the  plug  against  which 
it  bears,  is  of  hardened  steel. 

The  pressure  plate  is  held  in  its  correct  position  by  projections 
in  the  che^t,  on  one  side,  and  tongues  projecting  from  the  cover 
on  the  other,  which  bear  against  it  near  each  end,  as  shown. 


284 


HANDBOOK    ON    ENGINEERING. 


Between  these  guides,  it  is  capable  of  motion  up  and  down  its 
inclined  supports,  and  also  directly  back  and  forth  between  the 
valve  and  the  cover. 

The  pressure  of  steam  is  always  on  this  plate,  and  tends  to 
force  it  down  the  incline  to  rest  on  the  valve.  By  means  of 
the  screw  it  is  forced  against  the  steam  pressure,  up  the  in- 
clines and  away  from  the  valve.  This  adjustment  is  capable  of 
great  precision,  so  that  the  valve  works  with  entire  freedom 
between  its  opposite  seats,  and  still  is  steam-tight. 

How  these  plates  act  as  relief  valves*  —  Whenever  the  pres- 
sure in  the  cylinder  exceeds  that  in  the  chest,  the  admission 


Fig.  1&4.    Cross-section  of  cylinder  and  valves. 

pressure  plate  is  instantly  moved  back  to  contact  with  the  cover, 
thus  affording  an  ample  passage  for  the  discharge  of  water 
before  it  can  exert  a  dangerous  strain.  This  plate  is  superior 


HANDBOOK    ON    ENGINEERING. 


285 


in  this  action  to  any  of  the  ordinary  forms  of  relief  valve,  both 
in  the  area  opened,  and  also  in  being  self -adjusted  to  the  pressure, 
and  opening  fully  the  instant  that  is  exceeded. 

How  to   keep   the  admission  valves  tight*  —  These  valves, 
though  moving  in  complete  equilibrium,  are  liable  to  slight  wear. 


Fig.  175.    Section  of  Porter-Allen  steam  valve. 

This  should  be  taken  up  as  it  appears,  by  letting  down  the 
pressure  plates.  The  construction  of  these  plates  and  the  method 
of  adjusting  them,  are  shown  in  the  accompanying  sections,  made 
through  the  steam  chest  at  one  end  of  the  cylinder.  Of  these, 
the  drawings  are  horizontal  sections,  showing  the  four-openings  of 


286 


HANDBOOK    ON    ENGINEERING. 


the  valve —  first,  when  commencing  to  open,  with  arrows  indicating 
the  course  of  the  steam  ;  and,  second,  at  the  extreme  point  of  its 
lap;  while  Figs.  176  and  177  are  vertical  sections,  showing  the 


Fig.  176.    Cross-section  of  pressure  plate. 

pressure  plate  —  first,  when  by  turning  the  bolt  d  forward  it  is 
forced  up  the  inclines  and  away  from  the  valve,  producing  a  leak ; 
and  second,  when  it  is  let  down  to  its  proper  working  position. 
A  is  the  port,  B  the  valve,  and  C  the  pressure  plate.  The  latter 


Fig.  177.  Porter- Allen  valve  and  pressure  plate, 
is  made  with  a  trussed-back  and  so  cannot  be  deflected  by  the 
steam  pressure.  Through  the  passage  thus  formed,  the  steam 
reaches  two  of  the  openings. 


HANDBOOK    ON    ENGINEERING.  287 

The  pressure  plate  rests  on  two  inclined  supports,  c,  c,  and 
the  pressure  of  the  steam  forces  it  down  these  inclines  as  far 
as  the  bolt  d  underneath  will  allow.  This  bolt  holds  the  plate 
just  off  from  the  valve,  so  that  the  latter  moves  freely, 
and  is  still  steam  tight.  Whenever  leakage  appears,  a  minute 
turning  of  this  bolt  backwards  lets  the  pressure  plate  down  and 
closes  it. 

Provision  is  made  for  readily  detecting  the  least  leakage,  as 
follows :  When  the  engine  is  warmed  up  in  its  normal  working 
condition,  open  the  indicator  cocks,  or  in  the  absence  of  these, 
remove  the  plugs  from  the  top  of  the  cylinder,  unhook  the  link 
rod,  and  set  the  valves  by  the  starting  bar  so  that  both  ports  are 
covered,  and  turn  on  the  steam.  If  the  valve  leaks  at  the  end  of 
the  cylinder,  which  is  not  then  open  to  the  atmosphere  or  the 
condenser,  the  steam  will  blow  out  at  the  opening  provided,  having 
no  other  outlet.  Then  let  down  its  pressure  plate  by  backing  the 
bolt  very  carefully  till  the  leak  disappears.  The  valve  should 
still  move  freely  when  the  leak  has  disappeared,  and  the  pressure 
plate  must  not  be  let  down  any  closer  than  is  necessary  for  this 
purpose. 

Leakage  at  the  opposite  end  of  the  cylinder  will  not  generally 
be  seen,  the  steam  escaping  freely  by  the  open  exhaust.  To  test 
its  valve  in  the  same  manner,  the  engine  must  be  turned  on  to  the 
opposite  stroke.  These  examinations  should  be  made  from  time 
to  time. 

In  the  small  engines, which  have  no  starting  bar,  the  valve  rod 
can  be  disconnected  and  moved  by  hand  to  test  this  point. 

An  engine  should  never  be  started  till  it  is  warmed  up.  The 
valves  warm  quicker  than  the  supports  on  which  the  pressure 
plates  rest,  and  are  tight  between  their  seats  by  expansion,  until 
the  temperatures  have  become  nearly  equalized.  Provision  for 
detecting  and  stopping  any  leak  of  steam  is  the  crowning 
excellence  of  this  valve. 


288  HANDBOOK  ON  ENGINEERING. 


DIRECTIONS  FOR  SETTING  THE  VALVES  OF  THE  PORTER- 
ALLEN  ENGINE. 

To  set  the  admission  valves*  —  Place  the  engine  on  one  of  its 
dead  centers  as  explained  on  page  195.  Then  raise  the  governor, 
bringing  the  center  of  the  block  between  the  centers  of  the 
trunnions  of  the  link. 

"With  the  governor  remaining  up,  set  the  valve  that  is  about 
to  open,  giving  to  it  a  lead  of  from  Ty  to  T3¥" ,  according  to 
the  size  of  the  engine.  High  speed  requires  considerable  lead. 
Repeat  this  for  the  other  valve  on  the  opposite  center. 

On  letting  the  governor  down,  the  crank  remaining  on  the 
dead  center,  it  will  be  seen  that  the  valve  is  moved  a  short  dis- 
tance. This  motion  of  the  valve,  produced  by  moving  the  block 
from  the  trunnions  to  the  extremity  of  the  link  while  the  crank 
stands  on  the  center,  is  the  same  in  amount  on  either  center  and 
takes  place  in  the  same  direction ;  namely,  towards  the  crank. 
Its  effect  is,  therefore,  to  cover  the  port  nearest  the  crank  and  to 
enlarge  the  opening  of  the  port  farthest  from  it ;  so  that  the  lead, 
which  is  equal  at  the  earliest  point  of  cut  off,  is  at  the  crank  end 
of  the  cylinder  gradually  diminished,  and  at  the  back  end  increased 
in  the  same  degree  as  the  steam  follows  farther. 

The  effect  of  this  is  to  equalize  the  opening  and  cut-off  move- 
ments, so  that,  on  setting  the  governor  at  any  elevation  whatever 
and  turning  the  engine  over,  the  openings  made  and  the  points  of 
cut-off  will  be  found  to  be  identical  on  the  opposite  strokes,  from 
the  commencement  up  to  the  maximum  admission.  This  differ- 
ence in  the  lead  is  also  singularly  adapted  to  the  difference  in  the 
piston  velocity  at  the  two  ends  of  the  cylinder. 

In  case  the  indicator  shows  that  the  lead  of  either  admission 
valve  requires  to  be  changed,  this  is  done  without  opening  the 
chest,  by  lengthening  or  shortening  the  stem  at  the  socket  of 


HANDBOOK    ON    ENGINEERING. 

its  guide,  bearing  in  mind  that  each  valve  moves  towards  the 
middle  of  the  cylinder  to  open  its  port. 

To  set  the  exhaust  valves*  —  These  have  an  invariable  motion, 
and  are  admirably  adapted  to  their  purpose.  They  are  set  so  as 
to  open  before  the  end  of  the  stroke  enough  to  give  ample  lead, 
and  close  again  when  the  piston  is  on  the  return  stroke,  early 
enough  to  effect  the  required  compression. 

All  the  valves  are  held  between  pairs  of  brass  nuts,  of  which 
the  inner  one  is  flanged.  These  nuts  must  be  securely  locked, 
and  should  be  so  set  upon  the  valve  that  it  is  free  to  adjust  itself 
between  the  nuts  while  yet  sufficiently  tight  that  no  ' '  lost  motion  ' ' 
exists.  To  avoid  the  consequences  of  a  mistake,  care  should  be 
taken,  before  closing  the  valve  chests,  to  turn  the  engine  slowly 
through  an  entire  revolution,  while  the  movements  of  the  valves 
are  carefully  watched,  so  as  to  insure  that  they  have  not  been  so 
set  as  to  bring  the  valves  or  their  nuts  into  contact  with  the  ends 
of  the  chest  at  the  extremes  of  their  movements. 

The  governor*  —  The  Porter  governor,  original  in  its  type, 
stands  unexcelled  as  adapted  to  stationary  engines,  requiring  close 
regulation.  The  active  parts  are  very  light,  the  power  being 
derived  from  a  high  rotative  speed,  causing  a  sensitiveness  in  its 
movements  that  will  arrest  fluctuations  and  produce  uniformity  in 
the  running  of  the  engine.  It  has  been  so  perfected  that  at  the 
present  day  it  is  easily  adapted  to  the  requirements  of  any  class 
of  work  necessitating  a  governor,  and  is  especially  desirable  for 
an  engine  where  a  steady  speed  is  necessary. 

The  speed  of  this  governor  being  constant,  makes  it  equally 
efficient  upon  an  engine  running  either  at  a  high  or  low  number 
of  revolutions.  That  is  to  say,  the  speed  of  engine  can  be 
altered  from  time  to  time  by  changing  the  governor  pulley,  the 
governor  itself  continuing  to  run  at  the  same  speed  and  under  the 
same  strains,  and  being  stationary,  it  is  always  open  to  observa- 
tiop- 


290 


HANDBOOK    ON    ENGINEERING. 


The  Ar mmgton  and  Sims  engine,  as  is  well  known,  is  of  the 
high  speed  type,  and  in  its  earlier  form  was  designed  with  double 
eccentrics,  one  inside  of  the  other.  These  eccentrics  are  operated 
by  the  shaft  governor,  and  the  compound  motion  produced  by  the 
movements  of  the  two  eccentrics  is  such  that  the  valve  has  equal 
lead  for  all  points  of  cut-off. 


Fig.  178.    Yalye  gear  of  the  Armington  &  Sims  automatic  engine. 


The  method  of  setting  the  valve  is  very  simple,  for  all  engines 
of  this  make  are  sent  out  with  the  valve  stem  and  slide  marked  at 
points  C  and  B  in  the  sketch,  and  these  points  should  be  set  just 
three  inches  apart.  The  following  are  the  directions  which  the 
builders  supply :  — 

"  If  the  distance  between  B  and  C  is  just  three  inches  you  will 
know  that  the  valve  is  all  right.  If,  however,  you  wish  to  put  in 
a  new  valve  and  adjust,  then  remove  the  steam-chest  cover  and 
place  the  engine  on  the  center  as  follows:  Place  line  marked  A, 
which  is  on  the  crank  pin  side,  with  line  on  opposite  side  of  rim 
marked  F  (not  shown  in  drawing),  level  with  engine;  now  take 
out,  or  loosen  up  the  springs  and  block  the  weights  out  so  that 
the  distance  betweendweights  and  pin  at  D  E  will  be  |  of  an  inch ; 
adjust  the  valve-stem  at  the  guide  so  that  by  turning  the  engine  over 


HANDBOOK    ON    ENGINEERING. 


291 


from  one  center  to  the  other  the  lead  will  be  the  same  at  both 
ports ;  then  make  a  new  mark  distinctly  on  the  valve-rod,  so  that 
the  distance  B  C  will  be  the  standard  three  inches.  See  Fig.  178. 
u  It  is  not  possible  to  reverse  the  direction  of  running  without 
sending  to  the  factory  for  new  parts.  The  governor  is  not  con- 
structed so  that  one  set  of  parts  can  be  used  for  running  both 
ways." 

THE  CARE  AND   MANAGEMENT   OF    HARRISBURQ  ENGINES. 

It  is  essential  to  the  successful  operation  of  any  high-class  and 
expensive  machinery,  that  the  person  in  charge  be  gifted  with  a 
fair  degree  of  intelligence  and  alertness,  and  while  it  is  not 
attempted  to  formulate  new  rules  as  a  guide  to  the  person  in 


Fig,  179.    Sectional  elevation   of  Harrisburg    standard  four-valve 
tandem  compound  engine. 

charge  of  an  engine,  the  fact  must  not  be  overlooked  that  a  great 
deal  depends  upon  the  skill  and  judgment  of  the  operator  himself, 
and  that  it  is  manifestly  impossible  to  give  rules  other  than  of  a 
general  character  and  which  may  frequently  have  to  be  modified 
to  suit  the  different  conditions  that  may  arise.  However,  the 


292  HANDBOOK    ON    ENGINEERING. 

following  are  some  suggestions  for  the  convenience  of  operating 
engineers :  — 

When  engines  of  these  styles  have  been  properly  erected,  the 
steam,  exhaust  and  drain  connections  completed,  and  the  piston 
and  valve  rods  packed,  the  operator  should  be  careful  to  see  that 
all  parts  are  in  proper  position  and  firmly  secured. 

The  bed  should  be  thoroughly  cleansed  inside  and  a  good 
quality  of  machine  oil  poured  into  the  reservoir  beneath  the  crank, 
until  it  is  just  in  contact  with  the  crank  disc. 

A  mineral  oil  only  should  be  used,  and  of  medium  viscosity. 
Fill  the  eccentric  lubricating  cup  and  flush  the  main  bearings 
with  the  oil. 

The  cylinder  lubricator  should  be  filled  with  a  first-class  qual- 
ity of  cylinder  oil,  of  heavy  body. 

The  best  oils  obtainable  are  the  most  economical,  without 
question. 

Careful  preparations  before  starting  engine*  —  The  cylinder 
and  steam  chest  drain  valve  should  now  be  opened,  and  the 
throttle  valve  carefully  started  just  enough  to  allow  a  small  quan- 
tity of  steam  to  flow  through  the  cylinder  and  out  through  the 
drain  pipes,  but  not  enough  to  actually  start  the  engine  in 
motion. 

After  the  cylinder  and  valves  have  been  thoroughly  heated 
and  any  water  standing  in  the  steam  pipes  thus  blown  off,  start 
the  oil  flowing  in  the  cylinder  lubricator  cup.  A  general  survey 
of  the  engine  should  now  be  taken  and  if  everything  is  found  to 
be  in  proper  condition,  carefully  open  the  throttle  valve  and  bring 
the  engine  gradually  up  to  speed,  when  it  should  be  noted  that 
the  governor  is  controlling  the  machine.  Examine  the  bearings 
and  eccentric  to  see  if  the  oil  is  flowing  properly,  and  make  sure 
that  every  part  is  operating  smoothly,  after  which  the  drain  valves 
may  be  closed. 

Adjustments  for  wear*  —  When  the  engine  has  been  in  opera- 


HANDBOOK    ON    ENGINEERING.  293 

tion  long  enough  to  necessitate  the  adjustment  of  the  working 
parts,  care  should  be  used  to  avoid  adjusting  them  so  close  as  to 
cause  heating,  and  the  following  general  rules  should  be 
observed :  — 

The  caps  on  the  main  bearings  should  always  have  sufficient 
liners  underneath  to  enable  the  nuts  on  the  bearing  studs  to  draw 
the  cap  down  solidly  upon  them  and  not  pinch  the  shaft,  which 
should  be  free  to  revolve  in  its  bearings  without  unnecessary  play. 

Adjustment  of  crank-end  connecting  rod*  —  In  adjusting  the 
connecting  rod  box  at  the  crank  pin  end  the  same  general  rules 
should  be  observed  regarding  the  liners  under  the  cap,  the  large 
nuts  drawn  solidly  upon  it,  the  small  nuts  firmly  jammed,  and 
the  cotter  pins  placed  in  position. 

The  adjustment  of  the  box  should  then  be  tested  with  a  lever 
about  12  inches  in  length,  the  adjustment  being  so  made  that 
with  a  lever  of  this  length  the  operator  can  easily  move  the  end  of 
the  connecting  rod  sufficiently  to  take  up  the  side  play  between 
the  flanges  on  the  crank  pin  and  the  ends  of  the  box.  The 
adjustment  should  never  be  made  so  close  that  this  side  movement 
cannot  be  observed. 

Adjustment  of  cross-head  pin  box*  —  The  adjustment  of  the 
connecting  rod  box  at  the  cross-head  pin  end  should  be  made  by 
removing  the  name  plate  from  the  engine  frame  and  placing  the 
crank  on  the  center  nearest  the  cylinder,  then  with  the  wrench 
provided  for  that  purpose,  slack  off  both  wedge  screws  at  the 
upper  and  lower  sides  of  the  connecting  rod,  and  draw  the  wedge 
up  until  it  is  solid  against  the  box,  then  slack  off  that  screw 
about  a  sixth  of  a  turn  and  draw  up  the  other  so  as  to  firmly  lock 
the  wedge;  this  method  prevents  the  box  from  pinching  the 
cross-head  pin. 

The  "  flats "  on  the  cross-head  pin  should  always  be  at  the 
top  and  bottom  to  avoid  wearing  a  shoulder,  and  the  nut  on  the 
end  should  be  drawn  up  firmly,  but  not  so  much  as  to  spring  the 


294  HANDBOOK    ON    ENGINEERING. 

bosses  of  the  cross-head  together,  nor  yet  enough  to  make  the 
box  tight  on  the  ends. 

Proper  adjustment  of  cross-head  in  the  guides  is  made  by 
liners  of  paper  or  tin,  placed  between  the  bronze  shoes  and  the 
body  of  the  cross-head. 

Adjustment  of  cross-head  shoes*  —  In  order  to  do  this  it  is 
necessary  to  remove  the  pin  and  the  end  of  the  connecting  rod 
from  the  cross-head,  and  with  a  wooden  lever  placed  in  the  pin 
hole  turn  the  cross-head  until  the  shoes  are  out  of  the  guides, 
then  remove  the  shoes  and  place  the  liners  beneath  them.  Care 
should  be  used  that  the  cross-head  does  not  fit  the  guides  too 
closely,  and  that  it  can  be  moved  freely  with  a  short  lever  from 
one  end  of  the  guides  to  the  other,  while  disconnected  from  the 
connecting  rod. 

The  cross-head  should  never  be  run  very  close  and  should 
always  be  free  enough  to  allow  long  and  continuous  runs  without 
causing  the  top  of  the  bed  over  the  guides  to  feel  uncomfortably 
warm  to  the  touch. 

Attachment  of  cross-head  to  piston  rod*  —  When  making  any 
adjustments  of  the  cross-head,  it  is  well  for  the  operator  to  assure 
himself  that  the  lock  nut,  which  prevents  the  piston  rod  from 
turning  in  the  boss  at  the  end  of  the  cross-head,  is  securely  in  place. 
All  but  the  largest  Harrisburg  engines  are  tested  under  steam 
before  leaving  the  works,  and  the  valves  set  with  the  indicator. 

The  distance  from  the  cylinder  head  end  of  the  valve,  when 
the  crank  is  on  the  center  nearest  the  cylinder,  is  marked  on  the 
end  of  the  cylinder  directly  underneath  the  steam  chest  cover. 
If  from  any  cause  the  valve  should  become  deranged,  place  the 
crank  on  the  center  described  and  with  a  scale  or  rule,  see  that 
the  valve  position  corresponds  to  the  dimension  marked  on  the 
end  of  the  cylinder ;  and  if  out  of  position,  it  can  easily  be  re- 
adjusted by  means  of  t^he  device  provided  for  that  purpose,  at  the 
outer  end  of  the  valve  stem. 


HANDBOOK    ON    ENGINEERING.  295 

On  the  Harrisburg  Ideal  engines,  where  the  ball  joint  con- 
nection is  used  between  the  valve  stem  and  the  eccentric  rod,  the 
wear  is  followed  up  by  filing  the  end  of  the  bronze  connection 
that  the  cap  is  screwed  against,  which  holds  the  ball  in  place. 
And  on  the  Harrisburg  Standard  engines,  where  the  ram  box 
connection  is  used,  the  adjustment  is  made  by  filing  the  half  of 
the  bronze  box,  which  is  attached  to  the  end  of  the  eccentric  rod 
that  connects  with  the  ram. 

Adjustment  of  eccentric  strap*  —  The  eccentric  strap  adjust 
ment  is  made  by  liners  placed  between  the  halves  of  the  strap  and 
double  nutted  bolts.  When  adjustment  is  necessary,  the  other 
end  of  the  eccentric  rod  should  be  disconnected  and  after  drawing 
up  the  strap  bolts  it  should  be  tested  by  giving  the  strap  a  half 
revolution  about  the  eccentric.  If  it  is  found  that  the  friction 
between  the  strap  and  eccentric  is  sufficient  to  support  the  weight 
of  the  rod,  the  bolts  should  be  loosened  until  the  strap  moves 
freely  without  lost  motion.  The  double  nuts  should  then  be 
locked  and  the  cotter-pins  replaced  in  the  ends  of  the  bolts. 

How  to  alter  engine  speed*  — The  governor  used  on  all  Har- 
risburg engines  is  the  centrally  balanced  centrifugal  inertia  type. 
A  few  words  of  explanation  may  be  of  service  to  operating 
engineers. 

The  weight  arms  are  constructed  with  differential  weight 
pockets,  to  allow  of  a  considerable  range  of  speed  adjustment 
without  altering  the  tension  of  the  springs.  If  an  increase  in 
speed  is  desired,  remove  weights  of  an  equal  thickness  from  the 
weight  pockets  of  the  levers,  and  add  weights  of  an  equal  thick- 
ness to  obtain  a  decrease  in  speed.  If  an  increased  speed 
causes  the  governor  to  "  race  "  or  "  weave,"  move  the  clamp  in 
the -slot,  to  which  the  outer  end  of  the  spring  is  attached,  farther 
from  the  small  end  of  the  weight  lever.  If  this  does  not  entirely 
correct  this  sensitive  condition,  screw  the  plug  into  the  spring 
until  the  racing  ceases.  If  the  decrease  of  speed  so  obtained 
renders  the  governor  too  sluggish  in  action,  move  the  clamp  in  the 


296  HANDBOOK    ON    ENGINEERING. 

slot  in  the  opposite  direction.  If  this  does  not  improve  the  regu- 
lation, and  the  speed  is  lower  than  desired,  add  weights  of  an 
even  thickness,  increasing  the  spring  tension  until  the  proper 
speed  is  obtained.  The  main  lever  bearings,  which  are  equipped 
with  anti-friction  steel  rollers,  should  be  oiled  about  once  a  week, 
and  taken  out  and  cleaned  about  once  a  month ;  the  other  joints 
fitted  with  compression  grease  cups,  should  be  treated  in  the  same 
manner.  About  once  a  month,  also,  the  springs  should  be  dis- 
connected and  the  governor  and  valve  gear  tested  by  hand,  to  make 
sure  all  joints  are  working  freely. 

The  foregoing  will  apply  also  to  the  Harrisburg  Standard  and 
Ideal  compound  engines,  and,  in  general,  to  the  Harrisburg  self- 
oiling  four- valve  engines.  Adjustment  for  wear  in  the  valve 
gear  connection  of  the  latter  type  of  engines  is  obtained  by  filing 
the  halves  of  the  bronze  boxes  on  the  ends  of  the  rods  connecting 
the  valves  with  the  wrist- plates  and  rocker  arms,  and  on  the 
wrist-plate  and  rocker  arm  pins,  by  means  of  bronze  shoes  let 
into  the  sides  of  the  bearings,  the  wear  being  followed  up  by  the 
screws  provided  with  lock-nuts,  and  all  bearings  lubricated  by 
means  of  compression  grease  cups.  The  Harrisburg  Corliss  en- 
gines,of  the  larger  sizes,  are  provided  with  quarter-boxes  in  the 
main  bearings  with  wedge  and  screw  adjustment,  and  are  built  self- 
oiling  or  otherwise,  according  to  size.  The  lubrication  of  the  prin- 
cipal bearings  is  accomplished  by  means  of  oil  cups,  and  the  valve- 
gear  connections  by  means  of  conveniently  arranged  grease  cups* 

McINTOSH    AND  SEYHOUR  HIGH   SPEED   ENGINE. 

How  to  set  the  valve*  —  When  the  engine  is  sent  out  from 
the  shop,  the  valves  are  set  and  trammed  with  three -inch  tram 
from  the  valve  rod  to  the  valve  rod  slide  at  0  D,  and  from  the 
eccentric  rod  to  the  eccentric  rod  head  at  E  F,  on  the  valve  slide 
end,  and  a  tram  is  furnished  with  the  engine,  or  a  new  tram  can 
be  made  with  exactly  three  inches  distance  between  the  points , 
which  will  suffice. 


HANDBOOK    ON    ENGINEERING. 


297 


In  case  the  tram  marks  become  lost,  or,  owing  to  wear  of 
the  valve  gear,  the  length  of  connection  is  altered,  the  proper 
procedure  is  to  put  the  engine  on  one  center,  and  then  on  the 


Fig.  ISO.    A  sectional   cut    of   Mclntosh  and   Seymour  high-speed 
engine,  showing  valve  and  governor. 

other,  and  observe  the  leads  which  occur  when  the  governor  is  in 
the  normal  position  of  rest.  See  Fig.  180.  The  lead  on  the  crank 
end  should  be  three  times  as  much  as  the  lead  on  the  head  end,  if 
the  connection  between  the  valve  and  eccentric  is  of  proper  length. 

When  the  valve  is  set  this  way,  the  cut-off  on  the  two  ends 
of  the  cylinder  will  be  approximately  equal  at  one-quarter  cut-off 
on  the  smaller  size  engines  having  inside  governors.  ; 

Preliminary  to  adjusting  connections  between  the  valve  and 
eccentric,  care  should  be  taken  that  the  mark  on  eccentric  G  H, 
corresponds  to  the  mark  on  the  pendulum. 

In  examining  the  steam  leads,  as  described  above,  it  should 
be  noted  that  the  surface  B  on  the  valve  has  nothing  to  do  with 
the  steam  distribution,  but  it  is  merely  to  give  ample  wearing  sur- 
face, and  that  the  steam  is  admitted  to  the  cylinder  through  the 
port  which  is  between  B  and  the  steam  edge,which  is  at  A*  and 
the  lead  should  be  measured  between  this  steam  edge  and  the 


298  HANDBOOK    ON    ENGINEERING. 

edge  of  the  port  leading  to  the  cylinder.  On  engines  of  larger 
size  having  outside  governors,  a  similar  method  should  be  em- 
ployed in  setting  the  valves,  except  that  the  trams  are  four  inches 
from  point  to  point,  and  should  be  used  between  the  valve  rod 
slide  and  valve  rod,  and  the  eccentric  rod  and  the  eccentric 

rod  head  at  governor  end,  instead  of  slide  end,  as  above. 

. 

INSTRUCTIONS    FOR   STARTING   AND  OPERATING   IDEAL 

ENGINES. 

Before  starting  engine*  —  Open  cylinder  cocks  and  throttle 
valves  sufficiently  to  warm  the  cylinder  and  valve.  Place  sufficient 
oil  in  the  basin  under  the  crank  so  it  will  stand  one  inch  above  the 
bottom  of  crank  discs.  When  receiving  a  new  "engine  from  the 
shops  with  visible  stuffing-box  and  water  drain,  before  tilling 
the  crank  case  with  oil,  previous  to  starting,  pour  water  in  opening 


Fig.  181.    The  Ideal  high  speed  engine. 

in  frame  into  pocket  under  piston  rod  stuffing-box,  until  water 
overflows  through  trap  connected  therewith  attached  to  outside  of 
frame.  Fill  cylinder  lubricator  and  start  it  to  feeding.  Fill  oil 


HANDBOOK    ON    ENGINEERING. 


299 


pump,  and  pour  engine  oil  into  pocket  on  main  bearings.  Fill 
eccentric  oiler  and  start  it  feeding.  After  the  steam  chest  and 
cylinder  are  warm,  turn  the  engine  over  by  hand  to  see  that  all  is 
free  and  right  to  start. 

Open  the  throttle  valve  gradually,  start  engine  slowly.  After 
the  engine  is  up  to  speed,  pump  five  or  six  strokes  of  oil  into 
cylinder  with  oil  pump.  The  oil  should  flow  in  streams  through 
both  pipes  on  the  crank  cover  into  the  pockets  of  the  main  shaft 
bearings. 

This  oil  passes  from  the  main  bearings  through  the  crank  pin 
and  is  distributed  over  cross-head  pin  and  slides.  Occasionally 
clean  out  the  oil  passages  in  crank  pin. 

Supply ,  as  needed,  a  little  fresh  oil  to  the  basin,  and  if  the 
oil  in  the  engine  bed  becomes  thick,  gritty  or  dirty,  so  as  not  to 
flow  freely  through  oil  passages,  draw  it  off  and  replace  with  fresh 
oil.  Filter  the  old  oil  and  use  it  over  continuously.  Use  a  pure 
mineral  oil  that  will  not  thicken  by  the  churning  it  receives. 

Serious  damage  and  cutting  of  the  cylinder  and  valve  will 
result  from  allowing  the  lubricator  to  cease  feeding,  even  for  a 
few  minutes.  If  the  engine  is  a  new  one  from  the  shops,  feed 
plenty  of  oil  through  the  lubricator  and  oil  pump  for  the  first 
few  weeks  after  starting.  Use  one  drop  of  oil  per  minute  for  each 
ten  horse-power,  or  ten  drops  per  minute  for  100  horse-power 
engine,  for  the  first  thirty  days  ;  after  which,  one-half  this  amount 
will  be  sufficient,  if  the  oil  is  of  good  quality.  If  the  boiler  is 
priming  or  foaming,  use  double  the  quantity  of  oil  to  protect  the 
cylinder  and  piston  from  cutting.  A  little  graphite  fed  into 
cylinder  is  very  beneficial. 

The  governor*  —  Fill  the  cups  on  governor  bearing  with  grease 
and  give  the  cap  J  turn  every  day.  Screw  the  cap  to  the  stuffing- 
box  on  dash-pot  loosely,  only  using  the  hand  to  turn  the  cap. 
The  governor  should  be  taken  apart  every  two  or  three  months 
and  bearings  cleaned  with  coal  oil  to  remove  gum.  If  governor 


300  HANDBOOK    ON    ENGINEERING. 

has  a  dash-pot,  it  should  be  refilled  with  glycerine  once  or  twice 
a  year.  Oil  may  be  used  in  the  dash-pot  in  place  of  glycerine, 
unless  the  engine  is  in  a  cold  room  where  the  oil  is  liable  to 
congeal.  To  refill  dash-pot,  unscrew  cover  on  end. 

In  taking  the  governor  apart,  allow  the  sliding  block, which 
holds  the  end  of  the  governor  spring,to  remain  with  its  outer  edge 
on  a  line  with  a  mark  across  the  face  of  the  slide,  and  in  re- 
adjusting the  spring,  place  the  same  tension  on  it  as  .before, 
which  can  be  ascertained  by  measuring  the  length  of  the  thread 
through  the  nuts  before  slacking  up  the  spring.  If  trouble  is 
had  with  springs  breaking  it  is  because  of  their  being  worked 
under  too  much  tension.  The  speed  of  the  governor  is  changed 
by  moving  the  weight  on  the  lever. 

To  increase  the  speed  of  the  engine,  move  the  weight  on  the 
governor  lever  near  to  the  fulcrum  pin.  To  reduce  the  speed, 
move  the  weight  out  toward  the  end  of  the  lever.  Tightening  the 
spring  will  also  increase  the  speed,  but  will  cause  the  engine  to 
"  race,"  unless  at  the  same  time  the  block,which  holds  the  end  of 
the  spring,  is  moved  toward  the  center  of  the  wheel.  The  proper 
way  to  change  the  speed  is  by  moving  the  weight,  allowing  the 
spring  to  remain  in  its  marked  position. 

Moving  the  block,  which  holds  the  spring,  towards  the  rim  of 
the  wheel,  will  make  the  governor  more  sensitive  and  regulate 
more  closely ;  but  if  moved  too  far,  this  will  cause  the  governor 
to  "  race."  Moving  the  block  towards  the  hub  of  the  wheel  has 
a  tendency  to  stop  the  u  racing,"  but  if  moved  too  far  the  speed 
of  the  engine  will  be  reduced  with  the  increased  load.  If  any  of 
the  bearings  of  the  governor  bind,  or  require  oiling  or  cleaning, 
the  governor  will  "  race."  These  bearings  should  be  kept  clean 
and  in  good  condition  and  the  stuffing-box  to  the  dash  pot  must 
not  be  screwed  up  tight,  as  that  will  cause  the  governor  to  "  race  ' ' 
when  set  for  close  regulation. 

The   face  of   the  slide  is   marked  with  a  line  where  the  outer 


HANDBOOK    ON    ENGINEERING. 

edge  of  block  which  holds  the  spring  should  be.  Figures  stamped 
on  the  face  of  the  slide,  give  length  of  end  of  eye-bolt  extending 
through  nuts.  This  gives  the  right  tension  to  the  spring. 
Tightening  the  spring  will  give  closer  regulation,  but  will  cause 
the  governor  to  "  race  "  if  the  spring  is  too  tight.  "  Racing  " 
caused  by  over-tension  of  spring,  can  be  stopped  by  moving  block 
nearer  to  center  of  wheel. 

To  set  valve*  —  When  necessary  to  ascertain  if  the  steam 
valve  is  properly  set,  proceed  as  follows :  Take  off  the  cover  or 
elbow  on  outer  end  of  steam  chest,  so  access  can  be  had  to  end 
of  valve.  Turn  the  engine  over  until  the  valve  has  traveled  as 
far  as  it  will  go  towards  end  of  steam  chest.  Then  measure  from 
the  end  of  steam  chest  to  the  end  of  the  valve,  and  this  distance 
should  be  represented  by  the  figures  in  inches  and  fractions 
on  end  of  steam  chest.  If  measurements  do  not  agree,  set  valve 
by  screwing  the  valve  stem  at  the  ball  joint. 

Square*  braided  flax  packing  is  the  best  kind  for  piston  rod  and 
valve  stem.  Don't  screw  the  glands  up  tight ;  allow  them  to  leak 
a  little.  The  valve  stem  has  only  exhaust  steam  —  don't  pack  it 
tight.  Screw  it  up  by  hand  only.  Screwing  the  piston  rod  gland 
up  tight  may  cause  the  piston  to  thump  or  pound  the  cylinder, 
and  heat  and  cut  the  piston  rod. 

Safety  caps*  —  The  safety  caps  attached  to  drip  valve  under 
the  cylinder  are  intended  to  break,  in  order  to  save  damage  to  the 
engine  if  water  enters  cylinder.  They  will  protect  the  engine 
from  breaking  if  the  amount  of  water  is  not  too  large  to  pass 
through  the  valves  and  pipes.  If  they  break,  they  have  accom- 
plished their  purpose  and  new  ones  should  be  attached. 

Eccentric*  —  Take  up  lost  motion  by  reducing  the  brass  liners 
between  the  lugs  on  eccentric  strap,  and  unscrew  and  dis- 
connect the  ball  joint  on  the  eccentric  rod  to  see  that  the  eccen- 
tric strap  will  turn  freely  on  the  eccentric.  If  a  close  fit  it  will 
heat,  cut,  seize  and  break  the  eccentric  rod  or  valve  stem.  Allow 


302  HANDBOOK    ON    ENGINEERING. 

the  eccentric  strap  to  run  loose ;  no  harm  if  it  knocks  a  little. 
It  will  not  wear  out  of  round  on  account  of  running  loose  ;  it  is 
dangerous  to  run  with  the  strap  snug. 

Ball  joint* — Take  up  lost  motion  in  the  ball  joint,  on  the  valve 
stem,  by  unscrewing  the  joint  at  eccentric  rod  and  turning  or 
filing  off  the  face  of  the  brass  part  attached  to  the  valve  stem, 
so  as  to  allow  the  male  part  to  screw  in  a  greater  distance. 

Connecting  rod* — Take  up  the  lost  motion  on  the  crank  pin 
bearing  b}^  removing  the  cap  and  taking  out  two  of  the  steel 
liners ;  take  one  from  each  side,  put  the  cap  back  and  set  the 
nuts  up  snug.  Disconnect  the  cross-head  end  of  the  rod  by  re- 
moving cross-head  pin,  and  try  lifting  the  rod  up  and  down  to 
see  that  it  does  not  pinch  the  crank  pin.  If  it  pinches  the  pin 
when  the  bolts  are  drawn  up  snug,  place  the  liners  back  or  substitute 
thinner  ones.  Always  screw  the  cap  back  solid  on  the  liners,  and 
keep  in  sufficient  liners  so  the  cap  will  not  pinch  the  pin  when  the 
bolts  are  screwed  down  snug.  NEVER  RUN  THE  ENGINE  WITHOUT 

HAVING      THE      CAP      SCREWED      UP     SOLID    AGAINST    THE    ROD,    with 

liners  between  if  needed,  to  make  the  proper  fit.  When  liners 
are  removed  be  sure  to  take  out  an  equal  amount  from  each  side, 
because  taking  out  more  on  one  side  only  is  liable  to  throw 
the  cap  at  an  angle  in  tightening  up  the  bolts,  which,  in  time, 
will  cause  the  bolt  to  break  and  is  liable  to  wreck  the  engine. 

The  brass  in  the  cross-head  end  of  the  connecting  rod  is  set  up 
3y  a  wedge.  This  wedge  is  drawn  down  by  the  steel  bolt  until 
the  brass  is  forced  solid  against  the  shoulders  in  the  end  of  the 
connecting  rod,  which  prevents  any  movement  of  the  brass. 
The  upper  bolt  is  used  to  lock  the  wedge  in  position ;  also  in 
withdrawing  the  wedge  when  the  brass  is  to  be  removed. 

To  take  up  lost  motion  in  the  cross-head  end  of  the  connecting 
rod,  remove  the  brass  and  file  an  equal  amount,  even  and  square, 
from  each  edge  of  the  brass,  so  as  to  allow  the  brass  part  to  come 
up  to  the  pin.  When  filing  the  brass,  try  the  pin  in  the  rod 


HANDBOOK    ON    ENGINEERING. 

and  do  not  file  enough  to  allow  the  brass  to  pinch  the  pin  when 
the  wedge  is  screwed  down  solid.  If,  by  mistake,  too  much  is 
filed  off,  put  in  a  sheet  of  copper  or  sheet  brass  liner,  so  the 
wedge  may  be  drawn  snug  without  pinching  the  pin. 

Cross-head*  —  For  adjusting  the  lower  cross-head  slide,  take 
out  the  cross-pin,  turn  cross-head  J  round  with  the  lower 
brass  slipper  opposite  opening  in  engine  frame ;  loosen  nuts  and 
insert  paper  or  thin  metal  strips  between  cross-head  and  slipper. 
The  top  slide  will  never  require  adjustment.  The  lower  slide 
should  run  five  years  before  requiring  lining  or  adjustment. 
Turn  the  cross-head  pin  J  way  around  every  three  months.  This 
will  prevent  it  wearing  out  of  round. 

Main  bearings*  —  To  take  up  lost  motion  in  the  main  shaft 
bearings,  remove  the  cap  and  file,  scrape  or  plane  an  equal 
amount  from  each  of  the  babbitt  metal  liners  or  strips, which  are  in 
the  main  bearings  under  the  inside  edge  of  the  cap.  Remove  the 
metal  evenly,  so  the  liners  will  remain  of  equal  thickness  at  each 
end.  Do  not  remove  enough  from  the  liners  to  allow  the  cap  to 
pinch  the  shaft  when  the  nuts  are  screwed  down  snug.  If,  by 
mistake,  too  much  metal  is  removed,  put  in  paper  strips  on  top  of 
the  liners  so  the  cap  can  be  screwed  down  solid  without  pinching 
the  shaft.  Ascertain  when  the  cap  pinches  the  shaft  by  turn- 
ing the  engine  over  by  hand  ;  it  will  not  turn  freely  when  the  cap 
is  too  tight.  With  proper  care  the  main  bearings  will  run  two 
years  before  requiring  adjustment.  NONE  OF  THE  BEARINGS  OF 

THE     ENGINE    SHOULD     BE    SO    TIGHT    AS    TO    PREVENT    TURNING  THE 

ENGINE  FREELY  OVER  BY  HAND.  Always  test  the  engine  in  this 
manner  after  adjusting  bearings. 

If  a  bearing  heats*  stop  the  engine  immediately,  take  out  shaft 
or  box,  clean  out  the  cuttings,  scrape  smooth,  clean  out  oil  pass- 
ages and  run  bearings  loose. 

Heating  or  cutting  will  never  occur  if  liners  are  put  in  so  caps 
cannot  be  set  up  to  pinch  the  bearings  and  they  receive  proper 


304  HANDBOOK    ON    ENGINEERING. 

lubrication  with  oil  free  from  grit  or  dirt.  After  adjusting  any 
of  the  bearings,  run  the  engine  for  a  few  minutes  ;  then  stop  the 
engine  and  feel  the  bearings  which  have  been  adjusted  to  see  if 
they  are  running  cool.  This  precaution  may  obviate  having  to 
shut  down  the  engine  while  performing  regular  duty. 

Do  not  allow  the  engine  to  run  with  bearings  so  loose  as  to 
thump  or  pound,  as  this  will  cause  the  bearings  to  wear  out  of 
round.  If  the  shaft  or  wheels  run  out  of  true  or  wabble,  it  is 
because  the  main  bearings  are  loose  and  should  be  taken  up. 
The  engine  will  run  smooth  and  noiseless  if  bearings  are  properly 
adjusted. 

THE  STEAfl  CHEST. 

Fig.  J82  shows  a  section  through  cylinder  and  valve.  The  steam 
chest  is  bored  out  and  fitted  with  a  pair  of  cylinders  or  bushings, 


182.    Cylinder  and  valve  — Ideal  engine. 


which  have  supporting  bars  across  the  ports,  to  prevent  any  pos- 
sibility of  the  valve  catching  upon  the  ports. 

The  valve  is  of  the  hollow  piston  type  —  a  hollow  tube  with  a 
piston  at  each  end.    The  live  steam  is  entirely  upon  the  outside 

19 


HANDBOOK   ON   ENGINEERING. 


305 


of  this  piston,  pressing  equally  on  each  end ;  the  exhaust  steam  is 
entirely  on  the  inside  of  the  piston,  so  the  valve  is  perfectly  bal- 


Fig.  188.    Tandem  compound  Ideal  engine. 

anced  and  can  easily  be  moved  by  hand  when  under  full  boiler 
pressure. 

Fig.  \ 84  is  a  cross-section  of  cylinder  and  valve  of  the  Tandem 
Compound  engine.  The  cylinders  of  the  Ideal  Compound  engine 
inFig.  184,  the  stuffing-box  between  the  two  cylinders,  is  dispensed 
with  entirely.  It  is  replaced  by  a  long  sleeve  of  anti-friction 
metal.  This  sleeve  is  light  and  free  to  adjust  itself  central  with 
the  rod.  Grooves  are  turned  on  the  inner  surface,  so  as  to  form 
a  water  packing. 

Both  valves  of  engine  are  controlled  by  the  same  governor  on 
the  same  stem,  moving  together  and  varying  in  stroke  as  the  load 
and  steam  pressure  vary.  This  gives  the  advantage  of  automatic 
cut-off  in  both  cylinders  and  dispenses  with  the  complication  of 
double  eccentrics,  rock  arms,  slides  and  stuffing-boxes. 


306 


HANDBOOK    ON    ENGINEERING. 


and  keep  clearance  spaces  at  minimum,  which  thus  gives  a  quick 
and  wide  opening  at  the  beginning  of  the  stroke,  in  order  to 
reduce  the  pressure  on  exhaust  end  of  high-pressure  piston. 


Fig.  184.    Section  of  cylinders  of  Ideal  compound  engine. 

The  cover  of  this  valve  is  held  in  place  by  springs  and  will 
lift  and  prevent  excessive  pressure  in  the  cylinder  from  water  or 
other  causes. 


FOR  INDICATING  IDEAL  ENGINES. 


The  illustration,  Fig.  185,  shows  the  reducing  motion  attached 
to  engine  ready  for  taking  indicator  cards. 

To  apply  the  Ideal  indicator  rig:  Screw  slotted  stud  in 
cross-head  pin,  first  removing  the  cap  screw.  Set  the  slot  per- 
pendicular to  line  of  motion  of  cross-head.  Set  cross-head 
exactly  in  center  of  its  travel.  Fasten  on  top  of  bed  where  oil 
funnel  is  placed,  first  removing  the  oil  funnel. 

Lever  should  be  adjusted  so  it  will  travel  in  slot  without  strik- 


HANDBOOK    ON    ENGINEERING. 


307 


ing  bottom,  or  passing  out  at  top.  Make  sure  that  lever  wiE 
travel  freely  in  slot  without  binding.  Select  a  hole  on  string 
carrier  that  will  give  the  necessary  motion  to  indicator  drum. 


Fig.  185.    Method  of  attaching  indicator  to  Ideal  engine. 

With  string  attached  from  indicator  through  hole,  so  adjust  this 
carrier  that  lines  drawn  on  polished  surface  shall  come  exactly 
parallel  with  string.  Make  all  adjustments  while  cross-head  is 
in  center  of  its  travel. 


HOW  TO  SET  THE  VALVE  ON  A  WESTINGHOUSE  COMPOUND 

ENGINE. 


The  only  exact  and  final  setting  of  the  valve  is  by  means  of 
the  indicator.  As  the  valves  are  permanently  set  and  all  adjust- 
ments made  before  the  engine  is  shipped,  it  is  not  supposed  that 


308 


HANDBOOK    ON    ENGINEERING. 


1;he  engineer  will  have  occasion  to  reset  them.  'Should  the  neces- 
sity for  setting  the  valves  arise,  however,  the  following  method 
will  be  sufficiently  accurate :  Break  joints  and  take  off  the  throttle- 
valve.  The  steam  ports  in  the  bushing  will  then  be  seen  through 
the  steam  connection  S.  (This  opening  is  on  the  side  in  fact,  but 
is  here  shown  on  the  top  for  convenience.)  Bring  the  high- 
pressure  piston  exactly  to  the  top  of  its  stroke  by  turning  the 
shaft  in  the  direction  the  engine  runs.  This  may  be  ascertained 


Fig.  186.    Westinghonse  compoun        _ 

by  either  taking  off  the  water  relief  valve  and  measuring  through 

its  port,  or  more  conveniently,  by  bringing  the  middle  of  the  key- 
way  in  the  shaft  exactly  over  the  center  of  the  shaft.  The  key- 
ways  are  planed  exactly  with  the  cranks,  so  that  the  position  of 
the  key  way  is  the  position  of  the  high-pressure  piston.  With 
this  piston  at  the  top  of  its  stroke,  the  valve  edge  a  a,  should 
show  about  T^  of  an  inch  port  or  lead,  and  be  moving  towards 
the  right  when  standing  behind  the  engine.  If  out,  it  may  be 
brought  to  position  by  screwing  the  valve-stem  into  or  out  of  the 


: 


HANDBOOK   ON    ENGINEERING. 


309 


valve,  which  is  tapped  to  receive  it.     Be  sure  and  set  the  jam  nut 
solid  when  through. 


Fig.  187.    Cylinders  of  Westingliouse  compound. 
SOME  POINTS  ON  CYLINDER  LUBRICATION. 

In  the  first  place,  use  the  best  automatic  feed  cup  that  can 
be  secured.  Don't  be  satisfied  with  the  old-fashioned  direct 
feed,  or  a  cheap  automatic.  A  good  cup  will  save  many  a  hun- 
dred per  cent  on  its  cost  in  a  year.  Don't  get  the  kind  which,  on 
account  of  its  peculiarity  of  feed,  is  adapted  for  a  light  oil  only ; 
it  will  then  be  shut  out  from  using  a  dark  oil,  which  may 
be  far  more  serviceable  and  economical  in  every  respect.  Get 
a  cup  where  the  drop  of  oil  cuts  off  square  and  passes  either 
down  or  up  through  a  glass  tube  into  the  steam  pipe.  This 
kind  will  feed  oil  perfectly ;  it  is  well  to  use  this  kind. 

Take  good  care  of  the  cup.  Don't  let  it  leak  around 
the  glass  tubes  or  other  joints,  for  if  it  does  the  water  will  escape 
as  it  condenses,  and  the  oil  will  clog  up  the  escape  pipe  and 
stop  feeding.  Use  in  it  only  the  best  grades  of  cylinder  oil, 
made  by  large  manufacturers  of  established  reputation.  Don't 
run  in  the  cylinders  any  kind  of  poor  stuff  that  may  be  offered, 
because  it  is  cheap ;  it  is  a  dangerous  experiment.  Feed  a  good 


310  HANDBOOK    ON    ENGINEERING. 

oil  sparingly  —  don't  drench  the  cylinder.  Too  much  oil  is  a» 
bad  as  water  in  the  cylinder.  Engineers  have  been  known  to  run 
a  couple  of  quarts  per  day  of  cheap  oil  into  an  ordinary  sized 
cylinder,  and  thought  they  were  doing  just  right ;  this  is  positive 
abuse  of  an  engine.  In  almost  all  cases  where  too  much  oil  is  fed, — 
cut  it  down.  Two  to  four  drops  per  minute  on  engines  from  50 
to  150  H.  P.  are  all  that  is  necessary,  if  the  oil  is  good.  Just 
enough  to  do  the  work  and  no  more,  will  afford  best  results.  As 
long  as  the  valve  stem  does  not  cause  trouble,  rest  assured  the 
valves  are  working  smoothly. 

AUTOMATIC  LUBRICATORS. 

An  automatic  sight  feed  lubricator  should  be  furnished 
with  every  engine  which  enables  the  engineer  to  see  the  oil  as  it 
is  fed  drop  by  drop  to  the  engine.  The  construction  of  these 
lubricators  is  such  that  the  steam  entering  a  chamber  is  condensed 
and  this  water  of  condensation  finds  its  way  into  another  com- 
partment of  the  lubricator,  wherein  is  contained  the  oil  to  be  fed 
to  the  engine.  The  drop  of  water,  by  reason  of  its  greater  spe- 
cific gravity,  seeks  the  bottom  of  this  oil  compartment  and  forces 
out  an  equivalent  bulk  of  oil  into  the  steam  pipe,  whence  it  is 
carried  by  the  current  of  steam  into  the  cylinders  and  is  distrib- 
uted upon  the  wearing  surfaces  intended  to  be  lubricated.  This 
method  insures  regularity  and  economy. 

There  are  numerous  automatic  lubricators  made  by  various 
manufacturers  throughout  the  country,  many  of  which  will  per- 
form their  functions  successfully.  The  illustrations  on  the 
opposite  page  represent  what  may  be  called  the  standard  type  of 
hydrostatic  lubricator  employed  for  lubricating  the  valves  and 
pistons  of  steam  engines. 

This  is  the  up-feed  cup,  showing  an  external  view  and  sec- 
tional view  of  the  same.  Attachment  is  made  to  the  steam-pipes 


HANDBOOK    ON    ENGINEERING. 


311 


at  the  points  F  and  K.  In  operation,  the  condensing  chamber  F 
provides  for  the  condensation  of  steam, which  enters  at  the  pipe  F. 
This  water  of  condensation  passes  down  through  the  valve  D  and 
through  the  tube  P  shown  in  the  section  and  discharges  into  the 
bottom  of  the  oil  vessel  A.  This  vessel  is  filled  with  oil  when  the 
cup  is  started,  the  height  of  oil  being  shown  in  the  index  glass  J. 


Figs.  188  and  189.    Sight  feed  cylinder  lubricator. 


The  operation  is  as  follows :  The  valve  N  being  opened,  the  valve 
D  is  opened  and  the  drop  of  water  is  allowed  to  pass  from  the 
condensing  chamber  F  downward  through  the  water  tube  and  into 
the  bottom  of  the  oil  chamber  -4,  where  it  displaces  a  drop  of  oil 
of  equal  bulk  on  account  of  its  greater  gravity,  and  this  drop  of 
oil  is  forced  out  past  the  valve  E,  making  its  appearance  in  the 
feed  glass  H,  as  it  starts  on  its  way  to  the  steam-pipe.  It  is 
carried  by  the  current  of  steam  to  the  engine  and  lubricates  the 
valve  and  the  pistons.  When  the  oil  cup  is  empty,  the  valve  D 


312 


HANDBOOK    ON    ENGINEERING. 


is  closed  and  the  drain  valve  G  is  opened,  which  will  allow  the 
water  in  the  oil  chamber  to  be  blown  out  preparatory  to  the  re- 
filling at  the  plug  C.  By  opening  the  valves  G  and  Z>,  steam  will 
be  blown  through  the  sight  glass  J,  thereby  clearing  the  same 
from  any  clogging  up  of  the  oil,  which  would  disfigure  it.  The 
amount  of  oil  to  be  fed  by  the  lubricator  will  be  regulated  by  the 
valve  7),  controlling  the  amount  of  water  admitted,  and  the  valve 
E  controlling  the  discharge  of  the  oil  into  the  sight  glass.  The 
valve  N  is  to  be  left  wide  open  in  operation  and  its  object  is  to 
provide  jfor  the  accidental  breaking  of  the  glass  H. 


Fig.  190.    Proper  method  of  attaching  cup  to  prevent  the  oil  from 
dropping  into  the  well,  and  not  going  into  the  cylinder. 


These  cups  should  be  attached  to  the  steam  pipe,  in  strict  ac- 
cordance with  the  instructions  contained  in  the  box  in  which  the 
lubricator  is  packed.  The  greatest  enemy  to  proper  performance 
is  leakiness ;  all  joints  must  be  absolutely  tight,  otherwise  the 


HANDBOOK    ON    ENGINEERING.  313 

water  of  condensation,  instead  of  performing  its  duty  of  displac- 
ing the  oil,  will  ooze  out  at  the  leaks  and  the  cup  will  refuse  to 
work.  In  most  cases,  provision  is  made  for  a  column  of  water 
which  may  stand  12"  or  more  in  height  and  enable  the  cup  to 
work  more  positively,  by  giving  it  a  greater  pressure  in  the  dis- 
placement chamber,  due  to  the  height  of  the  column.  A  suitable 
oil  is  essential  to  the  proper  working  of  such  a  lubricator,  as  well 
as  to  the  proper  lubricating  of  a  steam  engine.  An  improper  oil 
will  not  feed  through  the  cup  as  it  should,  on  account  of  its  dis- 
position to  disintegrate  and  go  off  in  bubbles,  when  exposed  to 
the  heat  of  the  steam. 

SETTING  A  PLAIN  SLIDE  VALVE  WITH  LINK  NOTION. 

The  setting  of  a  slide  valve  operated  by  a  link  motion  does 
not  differ  materially  in  principle  from  the  method  pursued  when 
setting  the  ordinary  slide  valve  driven  by  one  eccentric.  A  link 
motion  may  be  considered  as  a  means  of  driving  a  valve  by  two 
independent  .eccentrics,  either  of  which  controls  the  functions  of 
the  valve  wholly  or  in  part,  according  to  the  position  of  the  link. 
Thus  when  the  link  is  in  either  extreme  position,  the  eccentric 
driving  that  end  of  the  link  in  line  with  the  link-block  pin  may  be 
considered  as  being  entirely  in  control  of  the  valve  action,  and, 
vice  versa,  when  the  link  occupies  the  other  extreme  position  of 
its  throw,  as  actuated  by  the  reverse  lever,  the  other  eccentric 
becomes  possessed  of  the  controlling  function.  Practically, 
however,  the  operation  of  the  link  motion  is  very  complicated  and 
the  movement  of  one  eccentric  materially  modifies  the  action  of 
the  other.  Since  the  interfering  action  is  least  at  the  extreme 
positions  of  the  link  and  greatest  in  mid-gear,  the  plan  is  followed 
of  setting  the  valve  with  the  link  in  full  gear  both  forward  and 
backward  motion,  and,  as  before  stated,  the  procedure  is  on  the 
theory  of  independent  action  of  the  eccentrics. 


314 


HANDBOOK    ON    ENGINEERING. 


In  the  accompanying  diagram,  a  link  motion  is  shown  driving 
a  plain  slide  valve  without  the  intervention  of  a  rocker.  Each 
eccentric  is  set  with  reference  to  the  crank  pin,  the  same  as  it 
would  be  with  a  simple  slide-valve  engine.  The  eccentric  A  is 
set  on  the  shaft  with  the  same  angular  advance,  QMO,  as  would 
be  required  for  an  ordinary  engine  to  run  in  the  direction  indi- 
cated by  the  arrow.  Now,  since  the  crank  pin  is  at  (7,  if  it  were 
necessary  to  reverse  the  simple  engine  with  one  eccentric,  it  would 
be  necessary  to  change  the  position  of  the  eccentric  so  that  instead 
of  being  ahead  of  the  bottom  quarter  line  QJf,  it  would  be  ahead 


Fig.  191.    Diagram  of  link  reversing  gear. 

of  the  top  quarter  line  PM  by  an  amount  of  angular  advance  made 
necessary  by  the  lap  and  lead  of  the  valve.  Therefore,  the  eccen- 
tric would  come  in  the  position  of  the  eccentric  A1,  or  with  its 
center  line  coinciding  with  MN^  giving  it  the  angular  advance 
PMN.  Now  it  should  be  clear  that  if  an  engine  is  to  be  equipped 
with  two  eccentrics,  so  that  it  may  run  with  equal  facility  in 
either  direction,  they  will  occupy  the  positions  A  and  A1.  We 
will  suppose  that  an  engine  having  a  link  motion  is  to  be  over- 
hauled and  the  valve  motion  to  be  properly  set.  This  will  mean 
that  the  eccentrics  will  be  properly  located  for  the  correct  angular 
advance,  and  that  the  eccentric  rods  will  be  adjusted  to  the  right 
length.  When  these  conditions  are  obtained,  the  valve  should 


HANDBOOK    ON    ENGINEERING.  315 

perform  its   functions  properly  in   both   forward  and  backward 
motions,  and  also  when  the  link  is  "  hooked  up." 

Before  starting  to  set  the  valve,  it  is  best  to  take  a  general 
survey  of  the  valve  motion  parts  and  see  if  the  eccentrics  are 
somewhere  near  the  proper  location  on  the  shaft  relative  to  the 
crank-pin.  If  they  are  obviously  much  out  of  position,  they 
should  be  shifted  and  adjusted  as  near  the  correct  position  as 
possible  by  the  eye ;  doing  this  at  the  beginning  will  often  save 
confusion  and  much  time.  The  dead  centers  will  be  found  by  the 
method  given  on  page  195.  The  operation  should  be  carefully 
performed,  as  upon  it  depends  the  success  of  the  work.  After 
having  found  the  dead  centers  and  having  them  marked  so  that  no 
mistake  will  occur  when  "  catching  "  them  with  the  tram,  the 
valve  positions  may  be  taken  for  the  four  positions  ,  that  is,  front 
and  back  centers  -in  forward  motion,  and  the  front  and  back 
centers  in  backward  motion.  Put  the  reverse  lever  in  full  gear  in 
one  motion  or  the  other,  whichever  is  most  convenient,  and  turn 
the  fly-wheel  in  the  direction  the  engine  would  run  for  the  given 
reverse  lever  position.  Suppose  the  link  stands  in  the  position 
shown  in  the  diagram,  the  fly-wheel  should  be  turned  in  the  direc- 
tion indicated  by  the  arrow  until  the  dead  center  is  reached, 
which  is  known  when  the  tram  drops  into  the  prick  mark.  The 
position  of  the  valve  is  then  noted  and  a  measurement  taken.  If 
the  valve  shows  the  steam  port  open,  measure  the  distance  with  a 
steel  scale,  or  it  may  be  done  by  sharpening  a  stick  wedge-shaped 
and  shoving  it  into  the  opening.  By  noting  the  depth  to  which 
it  goes  at  the  valve  face  the  opening  can  be  readily  measured  on 
the  removal  of  the  wedge.  We  will  suppose  the  distance  is  found 
to  be  4".  The  measurement  should  be  set  on  a  sheet  of  paper 

o 

laid  out  as  follows :  — 

FORWARD  MOTION.  BACKWARD  MOTION. 

Front  center,  Front  center, 

Back  centero  Back  center,  f"  lead. 


316  HANDBOOK    ON    ENGINEERING. 

It  will  be  seen  that  the  valve  opening  is  set  down  as  being 
|"  lead,  and  as  being  on  the  back  center  in  the  backward  motion. 
After  having  verified  the  measurement  taken,  the  engine  can  be 
"  turned  over  "  in  the  same  direction  as  before  until  the  opposite 
dead  center  is  caught  by  the  tram.  It  may  be  found  that  the 
valve  does  not  show  open  in  this  position  but  covers  the  steam 
port.  To  find  the  position  of  the  valve  edge  relative  to  the  steam 
port,  scribe  a  line  in  the  valve  seat  face  along  the  edge  of  the 
valve  and  then  turn  the  fly-wheel  until  the  valve  uncovers  the 
steam  port.  The  distance  the  valve  laps  over  when  the  crank  is 
on  this  dead  center  can  then  be  readily  measured.  Suppose  the 
distance  is  found  to  be  ^".  It  is  set  down  on  the  log  as 
follows :  — 

FORWARD  MOTION.  BACKWARD  MOTION. 

Front  center.  Front  center,  J"  blind. 

Back  center.  Back  center,  f "  lead, 

The  valve  position  is  put  down  as  being  £"  blind,  which  is  the 
same  as  saying  that  it  has  i"  negative  lead,  and  is  fully  as  com- 
prehensive as  the  latter  term.  The  reverse  lever  should  now  be 
thrown  into  the  opposite  gear  and  the  measurements  taken  for 
both  front  and  back  centers  the  same  as  has  been  described  for 
the  backward  motion.  It  may  now  be  supposed  that  when  all  the 
measurements  have  been  taken  the  log  reads  as  follows :  — 

FORWARD  MOTION.  BACKWARD  MOTION. 

Front  center,  J"  blind.  Front  center,  |"  blind. 

Back  center,  T5F"  lead.  Back  center,  f "  lead. 

When  in  forward  motion,  the  valve  is  open  Ty  on  the  back 
center  and  lacks  J"  of  being  open  when  the  crank  is  on  the  front 
center.  The  total  lead  due  to  the  angular  position  of  the 
eccentric  is  ^"  minus  J"  =  Ty.  One-half  the  total  lead  should 
be  given  to  each  edge  of  the  valve  so  that  it  will  be  necessary  to 
lengthen  the  eccentric  rod  Bl,  ^"  +  i"  =  -£s"  to  get  the  valve 


HANDBOOK    ON    ENGINEERING.  317 

fnto  its  proper  position.  A  little  reflection  will  show  the  reason 
for  lengthening  the  eccentric  rod  J51.  In  speaking  of  the  front 
and  back  centers,  they  are  taken  to  coincide  with  the  crank  and 
head  ends  of  the  cylinder.  When  the  piston  is  at  the  crank  end 
of  the  cylinder,  the  crank  is  on  the  front  center.  By  referring  to 
the  log  it  will  be  seen  that  to  adjust  the  backward  eccentric  rod 
B,  it  will  also  be  necessary  to  lengthen  it.  The  valve  is  |"  blind 
on  the  front  center  and  has  |<*  lead  on  the  back  center.  The 
total  lead  is,  therefore,  f"  minus  £"=  J".  One-half  J"=J", 
which  being  added  to  the  amount  the  valve  is  lapped  on  the  front 
center,  makes  J",  or  the  amount  the  eccentric  rod  B  will  have  to 
be  lengthened  to  make  the  valve  open  equally  at  each  end  of  the 
piston  stroke.  The  opening  the  valve  has  when  the  crank  is  on 
the  centers  is  called  the  lead  and  in  the  case  of  the  backward 
motion,  it  is  found  that  after  the  eccentric  rod  is  lengthened,  the 
lead  is  |",  which  -is  too  much  for  most  cases  and  in  this  one  we 
can  assume  that  -fa"  would  be  about  right. 

Before  explaining  the  adjustment  of  the  eccentric  for  the  cor- 
rect angular  advance,  it  will  be  in  order  to  call  attention  to  the 
necessity  of  making  the  adjustment  for  the  eccentric  rod  lengths 
first.  The  eccentric  rods  are  lengthened  or  shortened,  as  the 
case  may  require,  by  inserting  or  removing  liners  between  the 
eccentric  rods  and  straps  at  E.  Other  forms  of  construction 
provide  different  means  for  adjustment,  but  the  principle  is  the 
same  in  each.  It  will  be  noted  that  the  correct  length  for  the 
two  motions  is  obtained  by  adjusting  the  eccentric  rod  corre- 
sponding to  that  motion.  Any  attempt  to  correct  an  irregularity 
by  changing  the  length  of  the  valve  rod  F  will  result  erroneously, 
unless  both  eccentric  rods  require  the  same  amount  of  movement 
and  in  the  same  direction.  After  having  adjusted  the  eccentric 
rods  to  the  correct  lengths,  the  angular  advance  of  the  eccentric 
A  can  be  changed.  Place  the  crank  on  a  dead  center  and  have 
the  reverse  lever  thrown  in  the  backward  motion  and  then 


318  HANDBOOK    ON    ENGINEERING. 

loosen  the  set  screws  that  hold  the  eccentric  to  the  shaft  and  tarn 
it  towards  the  crank  until  the  valve  shows  open  J^" ,  and  then 
tighten  the  set  screws  on  the  shaft.  After  all  the  adjustments 
have  been  effected,  it  is  always  advisable  to  turn  the  engine  over 
again  and  catch  all  the  dead  centers,  so  that  the  correctness  of 
the  adjustments  can  be  verified.  After  taking  the  new  log,  it 
will  usually  be  found  that  some  slight  irregularities  have  been 
introduced,  especially  if  any  of  the  adjustments  have  been  consid- 
erable, as  the  changes  made  for  one  motion  will  affect  the  other 
slightly. 

The  link  motion  shown  in  the  cut  is  so  connected  that  the  lead 
increases  as  the  link  is  shifted  towards  the  center.  If  the  eccen- 
tric rods  be  oppositely  connected  to  the  link,  the  engine  will  run 
in  an  opposite  direction  for  a  given  reverse  lever  position  and  the 
lead  will  decrease  as  the  lever  is  shifted  towards  the  center.  The 
link  motion  for  hoisting  engines  is  quite  commonly  connected  in 
this  manner,  for  the  reason  that  the  engine  will  stop  when  the 
lever  is  put  on  the  center,  which  is  not  the  case  when  connected 
as  shown.  Of  course,  in  such  a  case,  the  admission  and  cut-off 
take  place  at  the  same  position  in  the  stroke  and  the  compression 
is  high,  but  with  a  light  load  the  engine  will  run  on  the  center, 
which  is  considered  objectionable  in  the  case  of  the  hoisting 
engine. 

VALVE-SETTING   FOR   ENGINEERS. 

Plain  slide- valve*  —  The  plain  slide-valve,  while  the  simplest 
valve  made,  is  perplexing  to  one  who  has  not  made  a  study 
of  it.  Unless  one  understands  the  principles  of  the  valve 
and  its  connections,  he  will  probably  meet  with  trouble  when  he 
attempts  to  set  it.  We  will  first  place  the  engine  (see  p.  195) 
on  the  dead  center,  and  will  simply  explain  the  other  steps 
that  have  to  be  taken.  In  the  first  place,  it  should  be  understood 
what  result  is  obtained  by  adjusting  the  position  of  the  eccentric 


HANDBOOK    ON    ENGINEERING.  319 

and  the  length  of  the  valve  stem.  The  position  of  the  eccentric, 
when  the  valve  is  set,  depends  upon  which  way  the  engine  is  to 
run  and  whether  the  valve  is  connected  directly  to  the  eccentric 
or  whether  it  receives  its  motion  through  a  rocker  which  reverses 
the  motion  of  the  eccentric.  When  the  valve  is  direct  connected, 
the  eccentric  will  be  ahead  of  the  crank  by  an  amount  equal  to  90°, 
plus  a  small  angle  called  the  angular  advance.  When  a  reversing 
rocker  is  used,  the  eccentric  will  be  diametrically  opposite  this 
position,  or  it  will  have  to  be  moved  around  180°  and  will  follow 
instead  of  lead  the  crank.  Shifting  the  eccentric  ahead  has  the 
effect  of  making  all  the  events  of  the  stroke  come  earlier,  and 
moving  it  backwards  has  the  effect  of  retarding  all  the  events. 
Lengthening  or  shortening  the  valve  stem  cannot  hasten  or  retard 
the  action  of  the  valve,  and  its  only  effect  is  to  make  the  lead  or 
cut-off,  as  the  case. may  be,  greater  on  one  end  than  on  the  other. 
The  general  practice  is  to  set  a  slide-valve  so  that  it  will 
have  equal  lead.  The  lead  is  the  amount  that  the  valve 
is  open  when  the  engine  is  on  tfre  center.  To  set  the  valve, 
therefore,  put  the  engine  on  the  center,  remove  the  steam-chest 
cover  so  as  to  bring  the  valve  into  view,  and  adjust  the  eccentric 
to  about  the  right  position  to  make  the  engine  turn  in  the  direction 
desired.  Now  make  the  length  of  the  valve-spindle  such  that  the 
valve  will  have  the  requisite  amount  of  lead,  say  T^  of  an  inch, 
the  amount,  however,  depending  upon  the  size  and  speed  of 
the  engine.  Turn  the  engine  over  to  the  other  center  and  measure 
the  lead  at  the  end.  If  the  lead  does  not  measure  the  same  as 
before,  correct  half  the  difference  by  changing  the  length  of  the 
valve-stem,  and  half  by  shifting  the  eccentric.  Suppose,  for 
example,  that  the  lead  proved  to  be  too  great  on  the  head  end  by 
half  an  inch.  Lengthening  the  valve-stem  by  half  of  this,  or  £ 
inch,  would  still  leave  the  lead  i  inch  too  much  on  the  crank 
end.  That  is  to  say,  the  valve  would  then  open  too  soon  at  both 
head  and  crank  ends,  and  to  correct  this,  the  eccentric  would 


320  HANDBOOK    ON    ENGINEERING. 

. 

have  to  be  moved  back  far  enough  to  take  up  the  other  quarter- 
inch.  Sometimes  it  is  not  convenient  to  turn  the  engine  over  by 
hand,  in  which  case  the  valve  may  be  set  for  equal  lead  as  fol- 
lows: To  obtain  the  correct  length  of  the  valve-stem,  loosen  the 
eccentric  and  turn  it  into  each  extreme  position,  measuring  the 
total  amount  that  the  valve  is  open  to  the  steam  ports  in  each 
case.  Make  the  port  opening  equal  for  each  end  by  changing  the 
length  of  the  valve-stem.  This  process  will  make  the  valve- 
stem  length  as  it  should  be.  Now  put  the  engine  on  a  center  and 
move  the  eccentric  around  until  the  valve  has  the  correct  lead  and 
fasten  the  eccentric  in  that  position.  This  will  determine  the 
angular  advance  of  the  eccentric. 

The  plain  slide  valve*  —  The  function  of  the  slide-valve  is 
to  admit  steam  to  the  piston  at  such  times  when  its  force  can  be 
usefully  expended  in  propelling  it,  and  to  release  it  when  its  pres- 
sure in  the  cylinder  is  no  longer  required.  Notwithstanding  its 
extreme  simplicity  as  a  piece  of  mechanism,  no  part  of  the  engine 
is  more  puzzling  to  the  average  engineer  when  the  problem  to  be 
solved  is  to  determine  beforehand  the  results  which  will  be  pro- 
duced by  a  given  construction  and  adjustment,  or  the  proportions 
and  adjustment  required  to  produce  given  results.  All  who  have 
had  any  experience  in  constructing  and  setting  slide-valves  are 
aware,  in  a  general  way,  that  the  events  of  the  stroke  cannot 
be  independently  adjusted;  for  instance,  a  cut-off  earlier  than 
about  -|  of  the  stroke. 

To  set  a  slide  valve*  —  The  valve  should  be  set  in  such  a  man- 
ner that  when  the  engine  is  on  the  dead  center,  the  part  admitting 
the  steam  to  the  cylinder  is  open  a  small  amountas  shown  in  Fig.  1 85 , 
which  is  called  lead.  The  object  of  lead  is  to  enable  the  steam 
to  act  as  a  cushion  against  the  piston  before  it  arrives  at  the  end 
of  the  stroke,  to  cause  it  to  reverse  its  motion  easily,  and  also  to 
supply  steam  of  full  pressure  to  the  piston  the  instant  it  has  passed 
dead  center.  The  lead  required  varies  in  different  engines  from 


HANDBOOK   ON    ENGINEERING 


321 


to  ^  without  regard  to  size  or  kind.    Fig.  192  also  shows  the 
position  of  eccentric,  which  should  always  be  set  ahead  of  the 


Fig.  192.    At  point  of  taking  steam 

crank  at  an  angle  of  90°,  plus  another  angle,  called  the  "  angular 
advance."  When  the  valve  is  to  have  lead  the  angular  advance 
must  be  a  little  greater  than  when  no  lead  is  desired. 


193.    At  point  of  cut-off. 
Fig.  J93  shows  the  position  of  eccentric  at  point  of  cut-off  ;  also 
position  of  piston. 


Fig.  194.    Position  when  compression  begins. 
Fig.  J94  shows  position  of  valve  when  compression  begins.    It 
also  shows   position  of  eccentric,     The  compression  at  the   left 

21 


322 


HANDBOOK    ON    ENGINEERING. 


end,  towards  which   the  piston  is  moving,  has  just  commenced, 
and  the  exhaust  is  about  to  take  place  from  the  other  end. 


Fig.  195.    At  point  of  taking  steam. 

Fig*  J95  shows  the  position  of  eccentric  and  valve  in  an  engine 
with  a  rocker-arm. 


fig.  106.    At  point  of  cut-off. 

Fig-  J96  shows  the  position  of  valve   and  eccentric  nt  point  of 
cut-off. 


Fig.  197.    Showing  point  of  compression. 


HANDBOOK    ON   ENGINEERING,  323 


CHAPTER     XIII. 

TAKING  CHARGE  OF  A  STEAH  POWER  PLANT. 

It  is  frequently  the  case  that  an  engineer,  on  assuming  charge 
of  a  steam  power  plant,  proceeds  as  though  he  were  thoroughly 
familiar  with  the  condition  of  the  engine,  boiler  and  entire  sur- 
roundings. He  plunges  headlong  into  his  duties,  without  first 
taking  his  bearings.  A  skillful  physician  on  taking  a  case,  would 
not  proceed  in  this  manner  ;  neither  would  a  lawyer.  The  physi- 
cian would  feel  the  patient's  pulse,  look  at  his  tongue,  take  his 
temperature,  observe  his  color  and  ask  a  number  of  questions,  all 
for  the  purpose  of  enabling  him  to  make  a  correct  diagnosis  of 
the  patient's  ailment.  The  first  duty  of  an  engineer,  when  he 
takes  charge  of  a  plant,  is  to  ascertain  the  arrangement  and  con- 
dition of  the  plant.  Since  the  boiler  is  the  most  important  mem- 
ber of  the  plant,  it  should  be  the  first  to  engross  his  attention,  and 
it,  together  with  its  connections,  should  be  examined  as  closely  as 
time  and  surrounding  conditions  will  permit.  He  should  look  the 
boiler  all  over,  internally  and  externally,  if  possible,  in  search  of 


324  HANDBOOK    ON    ENGINEERING 

mud,  scale,  grooving,  pitting  and  defective  braces.  The  furnace 
should  be  examined  next,  in  view  of  burnt-out  brickwork,  grate 
bars  and  door  linings.  It  may  be  that  the  furnace  has  distorted 
or  cramped  proportions,  or  it  may  be  too  large.  The  bridge-wall 
may  be  so  constructed  as  to  huddle  the  flames  in  one  spot  on  the 
fire  sheets  of  the  boiler ;  or  it  may  be  of  such  shape  and  in  such 
condition  as  to  cause  the  ignited  gases  to  become  dissipated  in 
the  combustion  chamber.  Even  the  combustion  chamber  itself 
may  require  the  service  of  a  bricklayer.  He  should  next  examine 
the  safety  valve  and  see  that  it  is  of  ample  capacity  to  relieve  the 
boiler  of  surplus  steam,  and  that  it  is  in  thorough  working  order. 
The  first  duty  of  an  engineer  when  entering  his  plant  at  any 
time,  is  to  ascertain  how  the  water  in  the  boiler  stands,  or, 
in  other  words,  just  how  much  water  the  boiler  contains.  He 
should  open  the  gauge  cocks  first  and  note  what  comes  from  each 
in  turn  ;  then  open  the  cocks  or  valves  connecting  the  glass  gauge 
and  note  the  water  line  there  shown.  He  should  also  blow  the 
water  column  out,  in  case  any  sediment  may  have  choked  any  of 
the  passages,  which  would  be  liable  to  give  a  false  impression  as 
to  the  actual  quantity  of  water  contained  in  the  boiler.  Should 
the  water  be  found  at  tho  correct  height,  he  may  now  proceed  to 
get  up  steam ;  open  the  damper,  pull  down  the  banked  fire  and 
spread  it  evenly  over  the  grate,  adding  a  quantity  of  green  fuel. 
Allow  the  steam  to  rise  slowly ;  do  not  force  it.  This  applies 
especially  to  raising  steam  in  a  boiler  which  has  been  cold,  as  the 
expansion  of  the  parts  of  the  boiler  due  to  the  heat  should  take 
place  slowly  and  evenly;  otherwise,  the  life  of  the  boiler  will  be 
shortened.  While  waiting  for  the  steam  to  come  up  to  the  desired 
point,  the  engineer  should  now  get  his  engine  ready  for  the  day's 
run.  Fill  all  the  oil  cups  and  cylinder  lubricator,  so  as  to  be 
ready  to  operate  as  the  engine  starts.  With  a  hand  oil  squirt 
can,  go  around  all  the  small  brasses,  connections,  etc.,  and,  in  a 
word,  well  lubricate  all  the  parts  where  friction  takes  place.  If 


HANDBOOK    ON    ENGINEERING. 

he  uses  an  oil  pump  for  the  cylinder  and  valves,  it  would  be 
well  to  inject  a  small  quantity  of  cylinder  oil  before  the  engine  is 
started,  while  the  stop-valve  is  open,  during  the  time  the  engine  is 
being  "  warmed  up."  After  the  engine  cylinder  is  warmed 
through,  the  fire  should  again  be  looked  at,  and  dealt  with 
according  to  the  indications.  Of  course,  the  water  gauge  glass 
must  be  looked  at  frequently,  not  only  while  raising  steam  in  the 
morning,  but  at  all  times  while  the  boiler  is  in  operation. 

Everything  being  in  readiness,  the  engine  is  started  slowly  at 
first,  the  speed  being  gradually  increased  until  the  limit  is  reached. 
The  day's  run  is  now  fairly  commenced.  A  boiler  should  be 
blown  down  one  gauge  every  morning  before  starting  the  day's 
run  to  get  rid  of 'the  mud,  scale  or  anything  that  is  held  in 
mechanical  suspension  in  the  water.  Before  starting  in  the 
morning  and  at  noon  is  the  best  time  to  do  this,  as  the  sediment 
has  settled  to  the  bottom  during  the  night,  after  the  circulation 
of  the  water  has  stopped.  When  blowing  a  boiler  down,  always 
remember  to  open  the  blow- valve  slowly  —  be  careful  not  to  blow 
too  long,  and  then  to  close  the  valve  slowly. 

An  engineer  or  attendant  cannot  be  too  careful  in  handling 
the  many  appliances  with  which  a  steam  plant  is  equipped.  The 
principal  things  to  which  an  engineer  should  give  his  attention 
during  the  operation  of  his  boiler  day  by  day  are,  as  follows: 
The  maintenance  of  the  water  at  the  proper  level,  as  near  as  pos- 
sible, and  avoiding  fluctuations  in  the  pressure  of  steam.  See 
that  the  firing  is  done  correctly  and  economically  so  as  to  obtain 
from  every  pound  of  coal  all  that  is  possible  under  the  con- 
ditions existing.  The  raising  of  the  safety  valve  from  its  seat, 
at  least  once  daily ;  the  blowing  out  of  the  water  column  twice 
daily,  or  oftener,  if  the  water  used  is  very  dirty ;  the  frequent 
opening  of  the  water  gauge  cocks,  or  try  cocks,  as  they  are 
sometimes  called,  and  not  depending  entirely  on  the  gauge  glass 
for  the  correct  height  of  water ;  the  blowing  down  of  the  boiler 


326  HANDBOOK    ON    ENGINEERING. 

one  gauge  every  day ;  the  keeping  of  all  valves,  cocks,  fittings, 
steam  and  water-tight,  clean  and  in  good  working  order. 

When  shutting  down  the  plant  for  the  night,  the  fires  should 
be  cleaned  out  and  the  live  coals  shoved  back  on  the  grates  and 
banked ;  that  is,  green  coal  should  be  thrown  upon  them,  suffi- 
ciently thick  to  cover  all  the  glowing  fuel.  Pump  in  the  water 
until  it  reaches  the  top  of  the  glass  gauge.  This  should  be  done 
to  insure  a  sufficient  quantity  from  which  to  blow  down  in  the  morn- 
ing, and  also  to  allow  for  any  small  leaks.  Then  close  the  cocks  or 
valves  connecting  the  glass  gauge.  Should  this  glass  break  dur- 
ing the  night  and  the  valves  be  left  open,  there  would  not  be  much 
water  to  start  with  in  the  morning.  Leave  the  damper  open  a 
little,  just  sufficient  to  allow  the  gases  which  will  rise  from  the 
banked  fires  to  escape  up  the  chimney.  Finally,  make  sure  that 
all  the  valves  about  the  plant  which  should  be  closed,  are  closed  ; 
and  all  those  which  should  be  left  open,  are  open.  Of  course, 
the  foregoing  is  applicable  to  a  plant  where  there  is  no  night 
engineer.  But  in  any  case,  no  matter  how  many  assistants  an 
engineer  may  have  under  his  control,  he  should  be  familiar  with 
all  details  of  the  plant  under  his  charge. 

One  of  the  most  important  points  in  connection  with  the  opera- 
tion of  a  steam  boiler,  is  the  preventing  of  corrosion,  both 
internally  and  externally.  One  of  the  best  aids  to  secure  the 
well  working  and  longevity  of  the  steam  boiler,  or,  in  fact,  the 
whole  plant,  is  by  being  regular  and  punctual  in  a  certain  course 
of  treatment,  which  has  been  proven  to  be  effectual  and  beneficial 
in  its  results.  All  conditions  do  not  require  the  same  methods  of 
treatment;  therefore,  it  is  absolutely  necessary  that  the  engineer 
in  charge  familiarize  himself  with  all  the  conditions  under  which 
his  plant  is  running,  for  then,  and  then  only,  can  he  intelligently 
prescribe  and  act  accordingly.  Above  all,  let  him  remember 
the  adage,  "  Eternal  vigilance  is  the  price  of  safety,"  especially 
where  a  steam  boiler  is  concerned. 


HANDBOOK  ON  ENGINEERING.  327 

ECONOMY  IN  STEAM  PLANTS. 

In  these  days  of  close  figuring  upon  expense  in  office  buildings 
and  manufacturing  plants,  what  may  at  first  appear  insignificant 
items  may  actually  make  all  the  difference  between  a  good  margin 
of  profit  and  an  actual  loss. 

The  fuel  expense  is  one  of  the  largest  in  the  operation  of  the 
majority  of  plants,  and  any  reduction  which  can  be  made  in  the 
amount  of  fuel  used,  while  maintaining  the  same  amount  of  power, 
is  considered  a  direct  gain.  The  evaporation  of  more  than  nine 
pounds  of  water  per  pound  of  coal,  is  looked  upon  with  suspicion 
by  many,  as  it  is  not  thought  possible  to  obtain  more  than  this 
amount  in  even  the  best  designed  and  well  regulated  furnaces  and 
boilers,  especially  when  the  firing  is  done  by  hand.  The  actual 
value  of  the  fuel  depends  upon  the  way  in  which  it  is  used,  fully 
as  much  as  on  any  other  factor.  The  heat  unit  in  the  coal  should 
be  as  much  as  possible  utilized,  as  in  one  pound  of  good  steam 
coal  there  is  about  14,000  B.  T.  U.,  and  about  10,000  of  this 
amount  can  be  utilized,  so  that  4,000  heat  units  are  lost.  The 
mixture  of  gases  in  a  furnace  depends  upon  the  amount  of  air 
used.  One  pound  of  coal  requires,  theoretically,  about  twelve 
pounds  of  air  to  bum  completely.  But,  in  practice,  about  twice 
this  amount  is  required  in  the  present  boiler  furnace.  To  have 
good  combustion  coal  requires  a  good  draft.  The  gases  are  con- 
sumed near  the  fire,  and  the  waste  gases  carry  the  heat  to  the 
boiler  on  their  way  to  the  stack.  The  boiler  ought  to  have  suffi- 
cient heating  surface,  or  the  hot  wasted  gases  ought  to  travel  a 
sufficient  distance  to  be  cooled  down  to  about  350  degrees  Fah- 
renheit ;  which  temperature  is  found  high  enough  to  produce  a 
good  draft  in  a  stack  of,  at  least,  100  feet  high. 

How  a  bad  draft  will  unnecessarily  increase  the  coal  bill,  is 
this:  That  of  all  the  fuel  burnt  to  perform  certain  work,  a  cer- 
tain proportion  is  consumed  to  keep  the  heat  of  the  furnace  up 


328  HANDBOOK    ON    ENGINEERING. 

to  say,  212  degrees  Fahr.,  without  making  any  steam  whatever 
which  is  available  for  work.  This  quantity  varies  from  20  to  30 
percent,  according  to  conditions,  which  are  affected  by  various 
causes,  such  as  leakages  of  steam,  air,  or  water.  Now,  the  only 
available  power  for  work  which  we  get  from  our  fuel  is  the  margin 
between  this,  say  thirty  per  cent  required  for  the  said  purpose, 
and  what  we  generate  above  that.  An  engineer  should  notice  the 
general  condition  of  his  boiler  or  boilers,  and  the  equipments  of 
same ;  he  should  examine  the  boiJer  both  inside  and  outside, 
ascertain  the  dimension  of  grates,  heating  surfaces,  and  all  im- 
portant parts.  The  area  of  heating  surfaces  is  to  be  computed 
from  the  outside  diameter  of  water-tubes,  and  the  inside  diameter 
of  fire-tubes.  All  the  surfaces  below  the  main  water  level  which 
have  water  on  one  side  and  products  of  combustion  on  the  other, 
are  to  be  considered  as  water-heating  surfaces.  If  he  finds  that 
the  boiler  does  not  come  up  to  what  he  thinks  it  should,  he  should 
put  the  boiler  and  all  its  appurtenances  in  first-class  condition. 
Clean  the  heating  surfaces  inside  and  outside  of  boiler,  remove 
all  scale  from  flues  and  inside  of  boiler ;  remove  all  soot 
from  inside  of  flues,  all  ashes  from  the  flame-bed  or  com- 
bustion chamber,  and  all  ashes  from  smoke  connections.  Close 
all  air  leaks  in  the  masonry  and  poorly  fitted  cleaning  door. 
See  that  the  damper  in  britching  or  smoking-flue  will  open  wide 
and  close  tight.  Test  for  air  leaks  through  the  crevices,  by 
passing  the  flame  of  a  candle  over  cracks  in  the  brick  work.  A 
good,  attentive  fireman,  who  understands  his  business  and  will 
keep  his  bars  properly  covered  without  choking  his  fires,  is  really 
worth  double  the  wages  of  an  ignorant  or  inattentive  one,  as  his 
coal  bills  would  certainly  prove.  All  an  engineer  can  do  is  to 
keep  the  steam  piston  and  valve  or  valves  tight.  Also  the  drains 
from  his  engine,  and  all  drains  on  steam  traps  in  the  plant  tight ; 
also,  his  engine  cleaned  and  well-oiled,  and  not  keyed  up  too  tight. 
If  in  a  heating  plant,  he  should  see  that  the  back  pressure  valve  is 


HANDBOOK    ON    ENGINEERING. 


329 


at  all  times  tight,  as  it  does  not  take  much  of  a  le.ak  to  show  a 
difference  in  his  coal  bill  at  the  end  of  a  month.  He  should  keep 
all  valves  in  the  pumps  in  his  plant  tight,  and  see  that  the  pump 
piston  is  packed,  but  not  too  tight.  After  a  pump  is  packed,  he 
should  be  able  to  move  it  back  and  forth  by  hand ;  if  the  pump 
valves  leak  he  can  take  them  out  and  smooth  them  up  with  sand- 
paper. He  should  see  that  the  feed-water  to  the  boiler  is  at  least 
208  degrees  Fahrenheit ;  if  it  is  under  204  degrees,  his  heater  is  not 
right,  as  the  poorest  heater  will  heat  the  feed- water  to  204 ;  it 
would  be  well  to  overhaul  the  heater —  it  may  be  full  of  scale  ;  or, 
if  an  open  heater,  the  spray  may  be  off.  In  most  first-class 
plants,  the  feed-water  is  212  Fahrenheit. 

PRIMING. 

The  term  priming  is  understood  by  engineers  to  mean  the 
passage  of  water  from  the  boiler  to  the  steam  cylinder,  in  the 
shape  of  spray,  instead  of  vapor.  It  may  go  on  unseen,  but  it  is 
generally  made  manifest  by  the  white  appearance  of  the  steam  as 
it  issues  from  the  exhaust-pipe  as  moist  steam,  which  has  a  white 
appearance  and  descends  in  the  shape  of  mist,  while  dry  steam 
has  a  bluish  color  and  floats  away  in  the  atmosphere.  Priming 
also  makes  itself  known  by  a  clicking  in  the  cylinder,  which  is 
caused  by  the  piston  striking  the  water  against  the  cylinder  head 
at  each  end  of  the  stroke.  Priming  is  generally  induced  by  a 
want  of  sufficient  steam-room  in  the  boiler,  the  water  being  car- 
ried too  high,  or  the  steam-pipe  being  too  small  for  the  cylinder, 
which  would  cause  the  steam  in  the  boiler  to  rush  out  so  rapidly 
that,  every  time  the  valve  opened,  it  would  induce  a  disturbance 
and  cause  the  water  to  rush  over  into  the  cylinder  with  the  steam. 


HANDBOOK   ON   ENGINEERING. 


TABLE  OF  PROPERTIES  OF  SATURATED  STEAM. 


8 

2  . 

,3 

2 

8  5 

d 

«J 

rt 

§ 

Pressure  in 
pounds  per 
square  inct 
above  vacu 

Temperatu 
in  degrees 
Fahrenheit 

Total  heat 
in  heat  uni 
from  water 
at  32°. 

Heat  in  liqi 
from  32° 
in  units. 

Heat  of  vap 
Ization  or 
latent  heat 
heat  units. 

s?5 

tm 

££§§, 

Volume  of 
one  pound 
.in  cubic  fee 

Factor  of 
equivalent 
evaporatioi 
at  212°. 

Total  press 
above 
vacuum. 

1 

101.99 

1113.1 

70.0 

1043.0 

0  00299 

334  5 

.9661 

1 

2 

126.27 

1120  5 

94  4 

10-26.1 

0.00576 

17*  6 

.97*8 

2 

3 

141.62 

1125.1 

109.8 

1015  3 

0  0<>844 

118  5 

.9786 

3 

4 

153  09 

1128.6 

121  4 

1007  2 

0  01107 

90  33 

.98-22 

4 

5 

162.34 

1131  5 

130  7 

1000  8 

0  01366 

73  21 

.9852 

5 

6 

170.14 

1133.8 

138  6 

995.2 

0  01622 

61  65 

.9876 

6 

7 

176  90 

11*5  9 

145.4 

990.5 

0  01874 

53  39 

.9897 

7 

8 

182  92 

1137  7 

151.5 

986  2 

0.02125 

47.06 

.9916 

8 

9 

188.33 

1139  4 

256  9 

982  5 

0.02374 

42  12 

.9934 

9 

10 

193.25 

1140  9 

161  9 

979  0 

0  02621 

38  15 

.9949 

10 

15 

213  03 

1146.9 

181  8 

965  1 

0.03826 

26  14 

1.000* 

15 

20 

227  95 

1151.5 

196.9 

954  6 

0.05023 

19  91 

1.0051 

20 

25 

240.04 

1155.1 

209  1 

946.0 

0  06199 

16.13 

1  0099 

25 

30 

250  27 

1158.3 

219  4 

938  9 

0  07360 

13  59 

1.0129 

30 

35 

259.19 

1161.0 

228.4 

932.6 

0  08608 

11  75 

1.0157 

35 

40 

267.13 

1168  4 

236  4 

927.0 

0.09644 

10.37 

1.0182 

40 

45 

274.29 

1165.6 

243.6 

92-2.0 

0  1077 

9.285 

1.0205 

45 

50 

280.85 

1167  6 

250.2 

917  4 

0  1188 

8.418 

1.0225 

60 

55 

286  89 

1169  4 

256.3 

913  1 

0.1299 

7  698 

1  0245 

55 

60 

292.51 

1171.2 

261  9 

909  3 

0  1409 

7-097 

1.0263 

60 

65 

297  77 

1172.7 

267.2 

905.5 

0  1519 

6  58* 

1.0-280 

65 

70 

302  71 

1174.3 

272.2 

902  1 

0  1628 

6  143 

1.0295 

70 

75 

307  38 

1175.7 

276.9 

898  8 

0.17*6 

5  760 

1  0309 

75 

80 

311  80 

1177.0 

281.4 

895  6 

0.1843 

5  4;i6 

1.0323 

80 

85 

316.02 

1178  3 

285.8 

892  5 

0.1951 

5  126 

1  0337 

85 

90 

3-20.04 

1179  6 

290  0 

889  6 

0.2068 

4  859 

1.0350 

90 

95 

323.89 

1180  7 

294.0 

886  7 

0  2165 

4.619 

1.0362 

95 

100 

327  58 

1181  9 

297.9 

884  0 

0.2271 

4.403 

1.0374 

100 

105 

331  13 

1182.9 

301  6 

881  3 

0  2378 

4.205 

1.0385 

105 

110 

334  56 

1184  0 

305  2 

878  8 

0  2484 

4  026 

1  0396 

110 

115 

337.86 

1185  0 

308.7 

876  3 

0.2589 

3  862 

1.0406 

115 

!20 

341.05 

1186.0 

312.0 

874.0 

0.2695 

3.711 

1  0416 

120 

125 

344  13 

1186  9 

315.2 

b71  7 

0.2800 

3  571 

1.0426 

125 

130 

347.12 

1187  8 

318.4 

869  4 

0.2904 

3  444 

1.0435 

130 

140 

352.85 

1189.6 

324.4 

866  1 

0  3113 

3  212 

1  045* 

140 

150 

358.26 

1191  2 

830.0 

861  2 

0  3321 

3  Oil 

1.0470 

lf.0 

}£Q 

363  40 

1192.8 

335.4 

857-4 

0  3530 

2  833 

1.0486 

160 

170 

368  29 

1194.3 

340.5 

853  8 

0.3737 

2.676 

1  0502 

170 

180 

372.97 

1195  7 

345.4 

850.3 

0.3945 

2.635 

1.0517 

180 

190 

377.44 

1197  1 

350.1 

847  0 

0.4153 

2.408 

1  0631 

190 

200 

381.73 

1198  4 

354.6 

84*  8 

0.4359 

2.294 

1  0545 

200 

225 

891  79 

1201  4 

365.1 

8*6.3 

0  4876 

2.051 

1  0576 

2-25 

250 

400.99 

1204.2 

374.7 

829.5 

0.5393 

1.854 

1.0605 

250 

275 

409  50 

1206.8 

383.6 

823  2 

0.5913 

1  691 

1  06*2 

275 

300 

417.42 

1209.3 

391  9 

817  4 

0.644 

1  553 

1  0657 

3<0 

325 

424.82 

1211.5 

399.6 

811  9 

0.696 

1  437 

1.0680 

3-25 

360 

4*1  90 

1213.7 

406.9 

806.8 

0.748 

1.337 

1  0703 

350 

375 

438  40 

1215.7 

414  2 

801  5 

0  800 

1  250 

1.0724 

375 

400 

445.15 

1217.7 

421.4 

796  3 

0.853 

1.172 

1  0745 

400 

500 

466.57 

1224.2 

444.3 

779.9 

1.065 

.939 

1.0812 

600 

HANDBOOK   ON   ENGINEERING.  331 

The  gauge  pressure  is  about  15  pounds  (14.7)  less  than  the 
total  pressure,  so  that  in  using  this  table,  15  must  be  added  to 
the  pressure  as  given  by  the  steam  gauge.  To  ascertain  the 
equivalent  evaporation  at  any  pressure,  multiply  the  given  evap- 
oration by  the  factor  of  its  pressure,  and  divide  the  product  by 
the  factor  of  the  desired  pressure.  Each  degree  of  difference  in 
temperature  of.  feed-water  makes  a  difference  of  .00104  in  the 
amount  of  evaporation.  Hence,  to  ascertain  the  equivalent 
evaporation  from  any  other  temperature  of  feed  than  212°,  add  to 
the  factor  given  as  many -times  .00104  as  the  temperature  of 
feed-water  is  degrees  below  212°.  For  other  pressures  than  those 
given  in  the  table,  it  will  be  practically  correct  to  take  the  pro- 
portion of  the  difference  between  the  nearest  pressures  given  in 
the  table.  Example :  If  a  boiler  evaporates  3000  Ibs.  of  water 
per  hour  from  feed- water  at  200  degs.  Fah.  into  steam  at  100 
Ibs.  per  sqr.  in.  by  the  gauge,  what  is  the  equivalent  evaporation 
"  from  and  at"212°?  Ans.  3159.24  Ibs. 

Operation :  Temperature  of  feed-water  =  200  degs. 

Then,  212  —  200  =  12  —difference  in  temperature. 

Then,  15  added  to  the  gauge  pressure  =  115. 

Looking  in  the  above  table  we  find  the  factor  1.0406. 

Then,  .00104  X  12  =.01248. 

And,  1.0406 

.01248 
1.05308 

Then,  3000  X  1.05308  =  3159.24  Ibs.  the  equivalent  evapo- 
ration. 

The  H.  P.  of  this  boiler  would  be  91.57. 


332  HANDBOOK    ON    ENGINEERING. 

HIGH  PRESSURE  STEAM. 

It  is  generally  believed  that  high-pressure  steam  is  cheaper  to 
use  and  costs  but  little  more  to  generate  than  low  pressure  steam. 
A  study  of  a  table  of  the  properties  of  saturated  steam,  to  be 
found  on  another  page  in  this  book,  will  show  why  high-pressure 
steam  is  economical  to  generate,  and  a  few  calculations  will 
prove  instructive  by  showing  what  may  be  excepted  from  its  use. 
To  generate  one  pound  of  steam  at  25  Ibs.  pressure,  absolute, 
requires  an  expenditure  of  1,155  thermal  units,  and  to  generate 
steam  at  200  Ibs.  pressure,  absolute,  requires  1,198  thermal  units, 
or  an  increase  of  only  43  thermal  units  for  an  increase  of  175  Ibs. 
pressure.  Further  investigation  shows  that  the  temperature  of 
steam  at  25  Ibs.  pressure  is  240°  and  at  200  Ibs.  pressure,  382°, 
the  difference,  142,  being  the  number  of  degrees  that  the  tem- 
perature of  steam  is  raised  with  an  expenditure  of  43  thermal 
units.  To  put  it  in  another  way,  the  temperature  of  the  steam 
has  been  raised  nearly  60  per  cent,  with  an  increase  of  less 
than  4  per  cent  in  the  number  of  thermal  units.  It  is  con- 
venient to  consider  that  the  generation  of  steam  takes  place 
by  two  different  steps,  one  of  which  is  raising  the  water  from 
32°  to  the  temperature  corresponding  to  the  pressure  of  the 
steam,  and  the  other  is  giving  off  the  steam  at  this  pressure, 
which  process  absorbs  a  quantity  of  heat  that  becomes  latent 
or  non-sensible.  At  25  Ibs.  pressure,  the  sensible  heat 
required  to  raise  one  Ib.  of  water  from  32°  to  240°  is 
209  units,  and  to  raise  it  from  32°  to  382  degrees,  the 
temperature  of  steam  at  200  Ibs.  pressure  requires  355  thermal 
units.  The  increase  in  the  sensible  heat  of  the  water,  there- 
fore, is  355  minus  209  =  146  units,  or  about  the  same  as  the  tem- 
perature increase  for  these  two  pressures,  which  is  142°.  It  is  thus 
clear  that  the  total  increase  in  the  number  of  heat  units  in  steam 
raised  from  25  Ibs.  to  200  Ibs.  pressure  is  small  (43°  as  found 


HANDBOOK     ON    ENGINEERING. 

above)  because  the  laten  heat  absorbed  in  the  formation  of  the 
steam  decreases  as  the  pressure  increases.  It  requires  less  heat 
to  generaU  steam  froir  water  raised  to  382°  at  200  Ibs.  pressure, 
than  from  water  previously  raised  to  240°  at  25  Ibs.  pressure. 
To  generate  higher  pressure  steam,  therefore,  we  must  first 
apply  enough  heat  to  bring  the  water  to  a  temperature 
corresponding  to  the  higher  pressure.  This  heat  will  be 
nearly  proportionate  to  the  increase  in  temperature.  Then 
enough  heat  must  be  applied  to  the  water  to  generate  the  steam, 
the  amount  of  heat  required  for  this  purpose  decreasing  as  the 
pressure  increases.  The  combined  result  of  these  two  processes 
is  that  it  takes  only  a  very  small  increase  in  the  total  heat  to  pro- 
duce the  higher  pressure  steam.  The  idea  may  be  suggested  that 
if  this  higher  pressure  is  obtained  at  the  cost  of  so  small  an  expen- 
diture of  heat,  it  would  not  be  reasonable  to  expect  a  large  gain 
in  economy  from  it,  since  it  is  not  possible  for  the  steam  to  do  a 
greater  amount  of  work  than  the  equivalent  of  the  heat  which  it 
contains.  This  would  be  true  were  it  not  for  the  fact  that  the 
larger  part  of  the  heat  in  the  steam  is  rejected  during  the  ex- 
haust. To  illustrate,  suppose  an  engine  to  exhaust  at  atmos- 
pheric pressure,  or, at  about  15  Ibs.,  absolute,  and  that  the  steam 
is  saturated.  As  may  be  determined  from  the  steam  tables,  there 
would  be  ejected  1,147  heat  units  per  pound  of  steam^  or  51 
heat  units  less  than  were  found  to  be  in  a  pound  of  steam  at 
200  Ibs.  pressure.  That  is  to  say,  under  the  above  assumption, 
there  are  available  only  51  heat  units  per  pound  of  steam  to  do 
the  work  in  the  engine  cylinder  when  the  steam  pressure  is  200 
Ibs.  But  we  also  found  that  the  increase  in  the  heat  units  in 
raising  the  steam  pressure  from  25  to  200  Ibs.  was  43,  and  hence 
the  increase  in  proportion  to  the  number  available  is  large, 
although  the  increase  in  proportion  to  the  total  number  required 


334  HANDBOOK    ON    ENGINEERING. 

to  generate  the  steam  is  small.  This  shows  why  high-pressure 
steam  is  economical  to  generate  and  profitable  to  use.  It  should 
be  stated  that  the  only  way  in  which  the  full  benefit  can  be  de- 
rived from  high  pressure-steam  is  by  using  the  steam  expansively, 
keeping  the  terminal  pressure  at  release  as  low  as  possible.  We 
will  not  take  the  space  to  give  the  calculations  to  prove  this, 
but  will  compare  a  few  results  of  calculations.  Suppose  steam 
to  be  used  in  a  theoretically  perfect  engine  at  the  pressure 
of  25  Ibs.,  50  Ibs.,  100  Ibs.  and  200  Ibs.  We  will  assume  that 
in  each  case  the  cut-off  is  at  one-third  stroke,  giving  three 
expansions  and  a  terminal  pressure  of  one-third  the  initial  pres- 
sure. The  steam  consumptions  will  then  be,  respectively,  about 
16J,  16,  15  J,  and  14  Ibs.  per  horse-power,  showing  that  gain 
from  the  increase  in  pressure  is  very  slight.  On  the  other  hand, 
suppose  the  expansions  to  be  carried  to  the  atmospheric  pressure 
in  each  case.  The  consumptions  will  then  be  about  27,  15,  11 
and  8  Ibs.  respectively,  showing  a  marked  decrease. 

Still  another  point  should  be  mentioned  in  relation  to  the 
relative  gain  that  is  to  be  expected  with  the  increase  in  pressure. 
Comparing  the  last  figure,  it  will  be  observed  that  the  decrease 
in  consumption  when  the  pressure  increased  from  25  to  50  Ibs- 
was  27  minus  15  =  12  Ibs.,  or  44  per  cent.  Again,  when 
the  pressure  doubled  from  50  to  100  Ibs.,  the  consumption 
decreased  only  4  Ibs.,  or  27  per  cent;  and  when  the  pressure  was 
again  doubled  to  200  Ibs.,  the  consumption  only  decreased  3  Ibs., 
or  about  27  per  cent.  It  is  evident  from  this  that  the  saving 
from  an  increase  in  steam  pressure  grows  less  as  the  pressure 
increases,  and  this  is  found  to  be  the  case  in  actual  practice. 
There  is  another  reason  for  this,  also,  coming  from  the  losses 
incident  to  cylinder  condensation  and  re-evaporation,  which  is 
more  marked  where  there  is  a  wide  range  in  pressures  than  where 
the  pressures  are  more  uniform  throughout  the  stroke.  It  is  found 
that  where  the  steam  pressure  is  much  above  100  Ibs.  gauge  pres- 


HANDBOOK    ON    ENGINEERING.  335 

sure,  no  gain  will  result  from  a  further  increase  in  pressure  with- 
out compounding,  the  advantage  of  the  compound  engine  being 
that  the  extremes  of  temperature  in  the  cylinders  are  not  so  great 
as  with  a  simple  engine. 

USING   STEAfl   FULL   STROKE. 

The  steam  engine  is  nothing  in  the  world  but  an  enlargement 
upon  the  end  of  the  steam  pipe,  containing  a  piston  against 
which  the  steam  in  the  boiler  may  press.  The  piston  moves  a 
certain  distance,  and  then  the  steam  is  allowed  to  press  upon  its 
other  side,  while  the  steam  on  the  first  side  is  allowed  to  flow  into 
the  atmosphere  and  go  to  waste.  The  slide-valve  is  the  device  or- 
dinarily employed  to  admit  the  steam,  alternately,  to  opposite  sides 
of  the  piston,  and  to  permit  the  free  outflow  of  steam  from  the 
reverse  side  of  the  piston.  As  the  steam  presses  upon  the  pis  ton, 
the  piston  moves  forward  with  a  force  equal  to  the  pressure  of 
steam  per  square  inch,  multiplied  by  the  number  of  square  inches 
of  piston  surface.  Steam  occupies  the  entire  space  from  the  sur- 
face of  the  water  in  the  boiler,  to  the  piston  of  the  engine.  The 
steam  space,  therefore,  includes  the  steam  space  of  the  boiler,  the 
steam  pipe,  the  steam  chest,  and  the  cylinder  space  upon  one  side 
of  the  piston.  As  the  piston  moves,  the  entire  steam  space  be- 
comes a  little  larger,  by  reason  of  the  cylinder  space  becoming 
longer.  Thus  it  will  be  seen  that  all  of  the  steam  in  the  boiler 
and  pipe  and  engine,  would  expand  a  trifle  and  the  pressure 
become  somewhat  reduced,  were  it  not  for  the  fact  that  new 
steam  is  made  by  the  fire  as  fast  as  the  piston  moves  forward. 
By  this  means  the  steam  is  maintained  at  about  uniform  pressure. 
It  will  be  seen  that  the  pressure  is  produced  upon  the  piston 
by  the  generation  of  new  steam  from  the  water,  that  is,  the  fire 
causes  the  water  to  generate  a  quantity  of  steam,  and  this  quantity 
of  steam  forces  its  way  into  the  other  steam,  exerting  a  force 
upon  the  whole  body  of  steam  and  pushing  the  piston  ahead. 


336  HANDBOOK    ON    ENGINEERING. 

If  an  engine  piston  has  a  surface  of  100  square  inches  and 
a  stroke  of  ten  inches,  it  follows  that  the  piston  will  yield  a 
thousand  cubic  inches  additional  steam  space  by  its  movement 
during  one  stroke,  and  consequently,  the  fire  will  be  called  upon 
to  produce  1,000  cubic  inches  of  new  steam  for  each  single  stroke 
of  the  engine.  If  the  pressure  of  the  steam  be  eighty  pounds  to 
the  square  inch,  the  engine  piston  will  move  with  the  force  of 
8,000  pounds.  When  the  engine  has  completed  one  stroke,  we 
find  an  amount  of  power  exerted  equal  to  8,000  pounds  moved 
ten  inches,  and  we  then  open  the  exhaust  valve  and  empty  into 
the  atmosphere  1,000  cubic  inches  of  eighty-pound  steam.  We 
keep  on  doing  this  for  each  stroke.  Now  our  attention  is  par- 
ticularly called  to  the  fact  that  when  we  empty  the  steam  out  of 
the  cylinder,  it  is  just  as  good  as  when  it  went  into  the  cylinder ; 
that  is,  it  was  1,000  cubic  inches  of  steam  at  a  pressure  of  eighty 
pounds  to  the  square  inch,  and  when  it  goes  into  the  atmosphere 
it  will  expand  into  over  6,000  cubic  inches,  at  fifteen  pounds 
pressure  to  the  square  inch,  or  the  same  pressure  as  the  atmos- 
phere. This  1,000  cubic  inches  of  steam  which  we  dumped  out 
of  the  cylinder,  is  precisely  the  same  quality  of  steam  as  the 
steam  which  we  have  penned  up  in  the  boiler ;  and  which  we  have 
to  be  making  new  all  the  time  in  order  to  keep  the  engine  run- 
ning. Such  is  the  operation  of  the  steam  engine  which  receives 
its  steam  the  full  length  of  the  stroke ;  and  such  an  engine  may 
be  described  briefly,  as  a  very  wasteful  machine,  which  throws 
away  steam  as  good  as  it  receives  it,  and  which  requires  the  gen- 
eration of  a  cylinder  full  of  full  pressure  steam  for  each  stroke. 
It  should  be  readily  understood  that  when  the  piston  has  com- 
pleted its  stroke,  and  just  before  the  exhaust  valve  is  opened  to 
allow  the  steam  to  escape,  the  cylinder  contains  1,000  cnbic 
inches  of  steam  at  eighty  pounds  pressure,  which  it  is  capable  of 
expanding  into  many  thousand  cubic  inches  at  constantly  de- 
creasing pressure.  The  first  step  in  the  improvement  of  such  an 


HANDBOOK  ON  ENGINEERING.  337 

engine  would  be  to  so  arrange  things  as  to  get  some  benefit  from 
this  enormous  power  of  expansion.  The  full  stroke  engine  does 
not  get  one-half  of  the  power  before  it  throws  the  steam  away. 
The  engine  which  we  would  have  referred  to  would  yield  a  power 
of  8,000  pounds  moved  ten  inches  at  each  single  stroke ;  33,000 
pounds  moved  one  foot  in  one  minute  is  a  horse-power ;  66,000 
pounds  moved  half  a  foot  would  be  the  same.  An  engine  using 
steam  full  stroke  is  such  an  extravagant  contrivance  that  we,  now- 
adays, seldom  find  them  in  use.  There  are  certain  classes  of 
engines  built,  fitted  with  link  motions  for  driving  the  valve,  and 
they  are  arranged  so  as  to  carry  their  steam  full  stroke,  but  pro- 
vision is  also,  made  for  quickly  hooking  up  the  link  and  suppress- 
ing the  full-stroke  feature. 

SLIDE  VALVE  ENGINES. 

If  we  have  an  engine  arranged  to  receive  its  steam  full  stroke 
and  to  dump  the  steam  out  into  the  air  in  as  good  condition  as  it 
was  received,  and  we  wish  to  get  some  of  the  benefits  of  the 
expansive  power  of  the  steam,  there  is  a  simple  way  of  doing  it 
and  without  any  great  change  in  the  engine,  and  that  is,  to 
lengthen  out  the  slide  valve  so  that  after  the  cylinder  is  half  full 
of  steam,  the  valve  will  shut  and  let  no  more  steam  enter.  Dur- 
ing the  balance  of  the  stroke,  the  entire  power  comes  from  the 
gradual  expansion  of  the  steam  shut  up  in  the  cylinder,  and  it 
will  be  readily  seen  that  whatever  power  we  succeed  in  getting  out 
of  the  expansion  of  the  steam,  is  pure  gain.  The  lower  the  pres- 
sure of  the  steam  is  when  it  is  exhausted  into  the  air,  the  more  it 
has  expanded,  the  more  power  we  have  gotten  out  of  it,  and  the 
more  we  have  gained.  It  may  be  said  in  a  few  words,  that  all 
slide-valve  engines  are  now  arranged  to  work  their  steam  expans- 
ively. But  it  is,  unfortunately,  found  that  the  slide-valve  pos- 
sesses a  peculiar  defect,  which  prevents  the  system  being  carried 
very  far.  We  can  lengthen  out  a  slide-valve  so  as  to  cut  the 


338  HANDBOOK  ON  ENGINEERING. 

steam  off  at  nay  desired  point  of  the  stroke,  and  we  must  then 
increase  the  throw  of  the  eccentric  in  order  to  properly  operate 
the  long  valve.  But  the  minute  we  do  this  we  find  that  we  have 
interfered,  to  a  certain  extent,  with  the  proper  operation  of  the 
exhaust.  No  matter  what  we  do  about  the  admission  of  steam  or 
about  cutting  off  before  the  end  of  the  stroke,  we  must  arrange 
our  exhaust  to  take  place  at  a  certain  point  at  the  end  of  the 
stroke.  It  is  found  in  practical  operations  that  this  necessary 
quality  of  the  slide-valve  prevents  our  arranging  it  to  cut  off  the 
steam  properly  at  an  earlier  point  than  about  five-eighths  or  three- 
quarter  stroke.  The  consequence  is,  that  an  engine  with  two  feet 
stroke  will  receive  steam  18  inches,  then  have  6  in.  of  expansion. 
It  may  be  fairly  said,  in  a  general  way,  that  about  all  the  slide- 
valve  engines  now  manufactured,  cut  off  the  steam  at  about  five- 
eighths  or  three-quarters  stroke  ;and  it  may  be  further  said  that  this 
is  about  all  we  can  get  out  of  a  slide-valve  engine.  Even  the  trifling 
expansion  got  from  such  engines  as  this,  represents  an  immense 
amount  of  money  in  the  course  of  a  year  in  large  establishments, 
but  it  is  not  good  enough  for  anyone  who  seeks  even  a  decent 
investiment  of  money,  in  power-getting  appliances. 

REGULAR  EXPANSION  ENGINES. 

A  liberal  expansion  of  steam  being  desirable  and  the  slide- 
valve  proving  totally  incapable  of  providing  for  such  expansion, 
the  first  step  in  the  desired  direction  is  to  totally  discard  the 
slide  valve.  The  Corliss  valve  is  a  cylindrical  piece,  oscillating 
in  a  cylindrical  hole.  The  valve  does  not  fill  this  hole,  but  seats 
against  one  side  only.  Hence  the  fitting  qualities  are  about  the 
same  as  with  the  slide-valve  and,  in  fact,  the  principle  is  about 
the  same,  the  Corliss  representing  a  portion  of  the  slide-valve, 
rolled  into  the  form  of  a  cylinder  and  operating  in  a  concave  seat. 
We  must  not  only  discard  the  slide-valve  arrangement,  but  in 
the  valve  arrangement  which  we  select,  we  must  secure  an  abso- 


HANDBOOK    ON    ENGINEERING.  339 

lute  independence  between  the  steam  admission  part  of  the  sys- 
tem and  the  exhaust  part.  The  slide-valve  is  one  chunk  of  cast 
iron,  letting  in  and  cutting  off  steam  at  its  outside  edges,  and 
opening  and  closing  the  exhaust  by  its  inside  edges.  When  one 
of  these  valve  edges  moves,  everything  else  has  to  move.  There 
is,  consequently,  no  independence  of  action.  In  the  Corliss 
engine  there  are  parts  to  let  steam  into  the  cylinder  and  to  quit 
letting  it  in  at  the  proper  time,  and  there  are  valves  to  let  it  out 
at  the  proper  time,  and  they  are  perfectly  independent  of  each 
other  in  all  of  their  movements.  The  consequence  of  this 
arrangement  is,  that  the  steam  valve  may  open,  steam  flow  into 
the  cylinder,  the  valve  suddenly  shut  and  chop  the  steam  off 
short,  the  piston  move  forward  in  its  stroke  by  the  expansion  of 
the  confined  steam,  and  finally,  be  let  out  by  the  opening  of  the 
exhaust  valve,  which  has  all  the  time  stood  ready  for  the  dis- 
charge. Here  we  have  a  regular  expansion  engine.  We  can  cut 
the  steam  off  as  early  in  the  stroke  as  we  desire,  and  hence,  have 
any  degree  of  expansion  we  desire.  And  we  can  do  this  without 
interfering  with  the  exhaust  valves.  It  is  found,  in  practice, 
that  an  engine  cutting  off  at  about  one-fifth  of  its  stroke  and 
expanding  the  other  four  fifths,  will  yield  the  fairest  practical 
economy. 

AUTOMATIC  CUT=OFF  ENGINES. 

In  order  that  those  not  posted  may  understand  what  is  meant  by 
the  term  "  Automatic  Cut-off  Engines,"  we  will  have  to  go  back  a 
step.  Take,  for  instance,  a  full-stroke  engine.  It  ought  to  be 
well  understood  how  the  ordinary  governor  does  its  work.  Sup- 
pose, for  instance,  that  there  is  no  governor,  and  that  we  regulate 
the  speed  of  the  engine  by  having  a  man  stand  at  the  throttle-valve 
all  the  time.  If  the  engine  runs  too  fast,  he  shuts  the  throttle- 
valve  a  little.  This  makes  the  steam  pipe  so  small  that  the  steam 
cannot  flow  fast  enough  to  keep  the  pressure  up,  and  consequently 


340  HANDBOOK    ON    ENGINEERING. 

the  speed  goes  down.  If  the  engine  runs  too  slow,  he  opens  the 
throttle- valve  and  lets  the  steam  flow  free,  so  as  to  maintain 
higher  pressure.  Thus  it  will  be  seen  that  the  man  at  the  throttle 
regulates  the  engine  by  altering  the  pressure  with  which  the  steam 
acts  upon  the  engine.  An  ordinary  engine  governor  is  simply  a 
man  at  the  throttle.  When  the  engine  runs  too  fast  the  balls  fly 
out,  the  governor  valve  shuts  a  little  and  the  pressure  of  steam 
entering  the  engine  is  reduced,  and  so  on  through  all  the 
changes  continually  taking  place.  All  steam  engines,  in  which 
the  regulation  of  steam  is  effected  by  means  of  a  governor  operat- 
ing upon  a  throttle,  are  called  throttling  engines.  They  operate 
by  reducing  the  pressure  of  the  steam  admitted  to  the  engine,  and 
thereby  taking  so  much  of  the  vitality  out  of  the  steam.  It  is 
entirely  the  wrong  way  to  do  it.  After  once  spending  our 
money  to  get  up  pressure  in  the  boiler,  we  should  make  the 
greatest  possible  use  of  that  pressure,  so  long  as  we  are  taking 
the  steam  from  the  boiler.  It  is,  therefore,  desirable  that 
the  full  boiler  pressure  should  be  admitted  to  our  cylinder; 
and  the  question  arises  as  to  how  we  shall  be  able  to  regulate 
the  speed  if  we  do  not  tinker  with  this  pressure.  The  automatic 
engine  regulates  the  speed  by  the  simple  act  of  altering  the  point 
of  cut-off.  If  the  engine  is  cutting  off  at  one-fifth  stroke,  we  get 
a  power  equal  to  the  incoming  force  of  steam  for  one-fifth  of  the 
stroke,  and  the  expansion  of  the  steam  for  the  other  four-fifths  of 
the  stroke.  If  the  engine  runs  too  slow  we  cut  the  steam  off  a 
little  later  and  thereby  increase  the  average  pressure  during  the 
expansion.  The  automatic  engine,  then,  is  an  engine, which  cuts 
off  the  steam  at  an  earlier  point  in  the  stroke,  if  the  engine  runs 
too  fast,  and  cuts  it  off  at  a  later  point  if  it  runs  too  slow.  It  is 
the  duty  of  the  governor  to  say  just  when  the  steam  valve  should 
close  and  not  let  any  more  steam  into  the  cylinder.  In  the  Cor- 
liss engine  the  steam  valves  open  wide  at  the  beginning  of  the 
stroke  and  let  full  boiler  pressure  smack  in  against  the  piston. 


HANDBOOK    ON    ENGINEERING.  Ml 

After  the  piston  has  advanced  to,  say  one-fifth  of  its  stroke,  the 
valve  shuts  up  as  quick  as  a  flash  and  the  expansion  begins.  If 
the  engine  starts  too  slow,  the  governor  will  hold  the  steam  valve 
open  a  trifle  longer,  but  will  not  interfere  with  its  full  opening  at 
the  beginning  of  the  stroke,  or  with  its  flash-like  closing  when 
the  cut-off  is  to  take  place.  During  all  these  operations  of  the 
governor  and  the  admission  valves,  the  exhaust  valves  are  let 
entirely  alone,  and  they  continue  their  work  unchanged.  It  will 
thus  be  seen  that  the  expansion  engine  makes  provision  for  the 
utmost  economy  in  the  use  of  steam,  and  with  the  automatic  fea- 
ture added  to  it,  provides  that  this  economy  shall  not  be  sacrificed 
for  the  purpose  of  regulating  the  speed. 

THE  GARDNER  SPRING  GOVERNORS. 

Construction*  —  Two  balls  are  rigidly  connected  to  the  upper 
ends  of  two  flat,  tapering,  steel  springs  —  the  lower  ends  of  the 
springs  being  secured  to  a  revolving  sleeve ,which  receives  rotation 
through  mitre  gears  ;  links  connect  the  balls  to  an  upper  revolv- 
ing sleeve,  which  is  free  to  move  perpendicularly. 

The  valve  stem  passes  up  through  a  hollow  standard  upon  which 
the  sleeves  revolve,  and  is  furnished  with  a  suitable  bearing  in  the 
upper  sleeve  ;  the  closing  movement  of  the  valve  is  upward,  and 
is  obtained  in  the  following  manner :  The  balls  at  the  free  ends  of 
the  springs  furnish  the  centrifugal  force  and  the  springs  are  the 
main  centripetal  agency  (gravity  is  not  employed).  As  the  balls 
fly  outward,  under  the  centrifugal  influence,  they  move  in  a  curved 
horizontal  path  which  may  be  described  as  an  arc,  modified  by  a 
radius  of  changing  length  —  the  radius  being  represented  by  the 
length  and  position  of  the  springs ;  the  links  represent  a  radius 
of  lesser  length,  while  the  sleeve  to  which  the  lower  ends  of  the 
links  are  pivoted,  being  free  to  rise  and  fall,  nullifies  the  effect  of 
the  links  in  determining  the  arc  in  which  the  balls  travel.  As  the 


342 


HANDBOOK    ON    ENGINEERING. 


balls  move  outward  in  their  peculiar  path,  the  sleeve  is  drawn  up- 
ward by  the  links,  and,  as  the  balls  move  inward,  the  sleeve  is 
pushed  downward.  The  change  of  speed  is  obtained  by  increas- 


Fig.  108.    The    Gardner    standard    governor  —  class 
automatic  safety  stop  and  speeder. 


"A"    with 


ing  or  decreasing  the  centripetal  resistance  >  and  accomplished  by 
the  action  of  a  spiral  spring  pivoted  against  the  lever,  and  by 
means  of  a  shaft  and  arm  against  the  valve-stem  in  the  direction 
to  open  the  valve  ;  a  thumb-screw  is  used  to  adjust  the  compres- 


HANDBOOK    ON    ENGINEERING. 

sion.  A  convenient  sawyer's  lever  is  attached  to  the  shaft  and 
a  reliable  automatic  safety  stop  is  furnished  when  desired. 

Fig>  f  98  on  the  preceding  page  represents  the  Gardner  Standard 
Governor,  Class  "A." 

This  is  a  gravity  governor,  having  an  automatic  safety  stop 
and  speeder.  It  is  made  in  sizes  from  1  £  inches  to  16  in.,  and 
is  especially  adapted  to  the  larger  type  of  stationary  engines.  In 
action,  the  centrifugal  force  of  the  pendulous  balls  is  opposed 
by  the  resistance  of  a  weighted  lever,  the  speed  being  varied  by 
the  position  of  the  weight.  The  automatic  safety  stop  is  very 
simple  in  construction  and  reliable  in  action.  It  is  accomplished 
by  allowing  a  slight  oscillation  of  the  shaft  bearing,  which  is  sup- 
ported between  centers  and  held  in  position  by  the  pull  of  the 
belt ;  a  projection  at  the  lower  part  of  the  shaft  bearing  supports 
the  fulcrum  of  the  speed  lever.  If  the  belt  breaks  or  sups  off 
the  pulley,  the  support  of  the  fulcrum  is  forced  back,  so  as  to 
allow  the  fulcrum  to  drop  and  instantly  close  the  valve.  The 
valve  is  not  affected  by  steam  current  and  both  valve  and  seats 
are  made  of  special  composition,  that  effectually  resists  wear 
and  the  cutting  action  of  the  steam.  The  governor  is  made  for 
all  pressures,  all  parts  being  made  by  the  duplicate  system,  with 
special  machinery. 

Fig,  199  on  the  following  page  represents  Class  "B"  gov- 
ernor—  a  combination  of  the  gravity  and  spring  designs. 

They  are  made  in  sizes  from  f  to  10  inches  inclusive,  and  are 
adapted  to  all  styles  of  engines.  They  are  provided  with  speeder 
and  sawyer's  lever,  but  are  not  automatic.  In  the  Class  "  B  " 
governor  the  centrifugal  force  of  the  pendulous  balls  operates 
against  the  resistance  of  a  coiled  steel  spring,  inclosed  within  a 
case  and  pivoted  on  the  speed  lever  by  means  of  a  screw ;  the 
amount  of  compression  of  the  spring  can  be  changed  so  as  to  give 
a  wide  range  of  speed.  A  continuation  of  the  speed  lever  makes 
a  convenient  sawyer's  hand  lever,  which  controls  the  valve  by 


344  HANDBOOK    ON    ENGINEERING. 

means  of  a  cord.     Sizes  £  to  1J  in.,  inclusive,  have  an  adjustable 
frame,  which  can  be  set  at  any  desired  angle  in  relation  to  the 


Fig.  199.    The  Gardner  standard  governor— Class  "B." 

valve  chamber.  The  valve  and  chamber  are  the  same  as  used  on 
Class  "  A  "  governor,  and  they  are  made  with  the  same  care  and 
style  of  workmanship. 


HANDBOOK   ON   ENGINEERING. 


345 


CHAPTER     XIV. 
A  FEW  REHARKS   ON  THE  INDICATOR. 

The  steam-engine  indicator  is  an  instrument  designed  to  show 
the  steam  pressure  in  the  cylinder  at  all  points  in  the  stroke.  It 
consists  primarily,  of  a  piston  of  known  area  capable  of  moving 
in  a  cylinder  and  resisted  by  a  coil  spring  of  known  strength. 
To  this  piston  is  attached,  by  means  of  suitable  piston  rod  and 
levers,  a  pencil  capable  of  tracing  a  line  corresponding  to  the 
motion  of  the  indicator  piston.  This  line  is  traced  on  a  paper 
slip  attached  to  the  drum  of  the  indicator,  which  drum  is  con- 
nected to  some  moving  part  of  the  engine  in  such  a  way  as  to  have 
a  back  and  forward  movement,  coincident  with  the  steam  piston 
of  the  engine. 


Fig.  200.    Exterior  and  interior  of  indicator. 

By  referring  to  the  above  sectional  view  of  an  indicator,  which 
is  generally  recognized  as  the  best  type,  the  construction  will  be 
readily  understood. 


346  HANDBOOK    ON    ENGINEERING. 

THE  USE  OF  THE  STEAH  EiNQINE  INDICATOR  IN  SETTING 
VALVES  AND  THE  INVESTIGATION  OF  SOME  OF  THE  DE- 
FECTS BROUGHT  OUT  BY  THE  INDICATOR  CARDS. 

The  steam-engine  indicator  has  come  into  such  general  use 
that  to-day  there  are  but  few  men  running  engines  who  are  not 
familiar  with  its  construction  and  manner  of  attachment  to  en- 
gines, and  the  method  of  calculating  horse  power  from  cards. 
The  indicator  is  attached  to  pipes  tapped  into  the  cylinder  heads, 
or  into  the  barrel  of  the  cylinder  opposite  the  counterbore,  beyond 
the  travel  of  the  piston  rings.  The  indicator  consists  of  a  cylin- 
der with  piston  and  compression  spring  and  a  drum  attached  to  a 
coiled  spring,  used  for  returning  the  same.  The  pressure  of  steam 
on  the  piston  of  the  indicator  compresses  the  spring  above  it. 
The  motion  of  the  piston  is  carried  by  a  piston-rod  to  a  pencil 
motion,  which  multiplies  the  motion  of  the  spring  some  five  or  six 
times.  The  springs  are  marked  20,  40,  80,  etc.  This  meaning 
that  80  Ibs.  pressure  per  square  inch  on  the  indicator  piston 
(or  whatever  the  spring  may  be  marked)  will  cause  the  pencil 
at  the  end  of  the  pencil-arm  to  move  an  inch.  The  pencil  marks 
on  paper,  which  is  fastened  on  a  drum.  This  drum  is  moved  by 
the  cross-head  of  the  engine,  through  some  form  of  reducing 
motion,  such  as  pantograph,  lazy-tongs,  brumbo  pulley,  etc.  To 
obtain  the  horse  power,  we  first  need  the  mean  pressure  equiva- 
lent to  the  variable  pressure  on  the  card.  This  is  most  easily 
found  by  dividing  the  area  of  the  card  by  the  length,  giving  the 
height  of  a  rectangular  card  of  equivalent  area,  and  then  multi- 
plying this  height  by  the  scale  of  the  spring.  The  mean  effective 
pressure  per  square  inch  on  the  piston,  times  the  area  of  the  pis- 
ton in  square  inches,  times  the  speed  of  the  piston  in  feet  per 
minute,  divided  by  33,000,  gives  the  horse  power.  If  there  is  a 
loop  at  either  end  of  the  card,  the  area  of  this  loop  is  to  be  sub- 
tracted from  the  larger  area  before  finding  the  mean  height  of 


HANDBOOK    ON    ENGINEERING. 


347 


the  card,  since  such  a  loop  represents  work  opposed  to  the  work- 
ing side  of  the  piston.  In  getting  areas  by  means  of  a  planimeter, 
no  attention  need  be  given  to  the  loops.  By  following  the  lines 
in  order,  as  drawn  by  the  indicator  pencil,  the  loops  will  be  sub- 
tracted from  the  main  card,  for  if  the  main  body  of  the  card  is 
traced  in  a  right-handed  rotation,  the  loops  will  be  traced  in  a 
left-handed  rotation. 

DIAGRAM  ANALYSIS. 

Figs*  20 J  and  202  are  from  throttling  engines  ;  the  former  repre- 
senting good  performances  for  that  class  of  engine,  and  the  latter, 


Fig.  201.    Diagram  from  a  throttling  engine. 

in    some  respects, which  the  engineer  will  readily  recognize,  bad 
performances* 


348  HANDBOOK    ON  ENGINEERING. 

. 

Figs.  203,  204,  and  205,  are  from  automatic8  ;  Fig.  203  repre- 
senting what  is  now  considered  rather  too  light  a  load  for  best 
practical  economy  ;  Fig.  204  about  the  best  load,  and  Fig.  205 
is  from  a  condensing  engine. 

Line  A  B  is  the  induction  line,  and  B  C  the  steam  line  ;  both 
together  representing  the  whole  time  of  admission. 

(7  is  about  the  point  of  cut-off,  as  nearly  as  can  de  determined 
by  inspection.  It  is  mostly  anticipated  by  a  partial  fall  of  pres- 
sure due  to  the  progressive  closure  of  the  valve. 

The  usual  method  is,  to  locate  it  about  where  the  line  changes 
its  direction  of  curvature. 

C  D  is  the  expansion  curve.     D  is  the  point  of  exhaust. 

D  E  is  the  exhaust  line, which  begins  near  the  end  of  the  stroke 
and  terminates  at  the  end  of  the  stroke,  or,  at  latest,  before  the 
piston  has  moved  any  considerable  distance  on  its  return  stroke. 

The  principal  defect  of  Fig.202  is, that  this  line  occupies  nearly 
all  the  return  stroke.  E  Fis  the  back  pressure  line,  which,  in 
non-condensing  engines,  should  be  coincident  with,  or  but  little 
above,  atmospheric  pressure.  In  Fig.  205  it  is  below  the  atmos- 
pheric line  to  the  extent  of  the  vacuum  obtained  in  the  cylinder. 
Some  authorities  would  call  it  the  vacuum  line  in  Fig. 205  but  that 
name  properly  belongs  to  a  line  representing  a  perfect  vacuum. 

jFMsthe  point  of  exhaust  closure  (slightly  anticipated  by  rise 
of  pressure)  and  F  A  the  compression  curve,  which,  joining  the 
admission  line  at  A,  completes  the  diagram  proper,  forming  a 
closed  figure. 

G  G  is  the  atmospheric  line  traced  when  the  piston  of  the  indi- 
cator is  subject  to  atmospheric  pressure,  above  and  below  alike. 
Some  pull  the  cord  by  hand  when  tracing  it,  to  make  it  longer 
than  the  diagram.  H  H  is  the  vacuum  line,  which,  when  re- 
quired, is  located  by  measurement  such  a  distance  below  the 
atmospheric  line  as  to  represent  the  atmospheric  pressure  at  the 
time  and  place  as  nearly  as  can  be  ascertained.  The  mean 


HANDBOOK   ON   ENGINEERING.  349 

atmospheric  pressure  at  the  sea  level  is  14.7  pounds.  For  higher 
altitudes,  the  corresponding  mean  pressure  may  be  found  by 
multiplying  the  altitude  by  .00053,  and  subtracting  the  product 
from  14.7.  When  a  barometer  can  be  consulted,  its  reading  in 
inches  multiplied  by  .49  will  give  the  pressure  in  pounds. 


FIfr.  202.    Diagram  from  a  throttling  engine. 

1  is  the  clearance  line*  representing  by  its  distance  from  the 
nearest  point  of  the  end  of  the  diagram  at  the  admission  end,  as 
compared  with  the  whole  length,  the  whole  volume  of  clearance 
known  to  be  present.  Its  use  is  mainly  to  assist  in  constructing 
ft  theoretical  expansion  curve  by  which  to  test  the  accuracy  of  the 
Actual  one. 

Calculating  mean  effective  pressure*  —  Since  the  simplification' 
«ad  popularization  of  the  planimeter,  no  engineer  who  has  occa* 


350 


HANDBOOK    ON    ENGINEERING. 


sion  to  compute  the  "  indicated  horse-power  "  (IHP)  of  engines 
should   be  without  one;  for,   if   properly   handled,    the  results 


Fig.  203.    Diagram  from  an  automatic  cut-off  engine* 

obtained  by  them  are  more  accurate  and  more  quickly  obtained 
than  by  any  other  process.  The  diagram  is  pinned  to  a  smooth 
board  covered  with  a  sheet  of  smooth  paper,  the  pivot  of  the  leg 
pressed  into  the  board  at  a  point  which  will  allow  the  tracing  point 
to  be  moved  around  the  outline  of  the  diagram  without  forming 
unnecessarily  extreme  angles  between  the  two  legs,  and  a  slight 
indentation  made  in  the  line  at  some  point  convenient  for  begin- 
ning and  ending  ;  for  it  is  vitally  important  that  the  beginning  and 
ending  shall  be  at  exactly  the  same  point.  The  reading  of  the 
wheel  is  taken,  or  it  is  placed  at  zero,  and  the  tracing  point  is 


HANDBOOK   OF   ENGINEERING. 


351 


passed  carefully  around  the  diagram,  following  the  lines  as  closely 
as  possible,  moving  right-handed,  like  the  hands  of  a  watch.  The 
reading  obtained  (by  finding  the  difference  between  the  two,  if 
the  wheel  has  not  been  placed  at  zero)  is  the  area  of  the  diagram 
in  square  inches,  which,  multiplied  by  the  scale  of  the  diagram, 
and  divided  by  its  length  in  inches,  gives  the  mean  effective 
pressure. 

The  process  of  finding  the  mean  effective  pressure  by 
ordinates* —  Divide  the  diagram  into  10  equal  parts  as  shown  by 
the  full  lines  in  Fig.  204 :  when  performing  this  work  a  frequent 
mistake  is  made,  viz., 


Fig*  204.    Erecting  the  or di nates. 

making  all  the  spaces  equal.     The  end  ones  should  be  half  the 
width  of  the  others,  since  the  ordinates  stand  for  the  centers  of 


352 


HANDBOOK    ON    ENGINEERING. 


equal  spaces.  Ten  is  the  most  convenient  and  usual  number  of 
ordinates,  though  more  would  give  more  accurate  results.  The 
aggregate  length  of  all  the  ordinates  (most  conveniently  measured 
consecutively  on  a  strip  of  paper)  divided  by  their  number,  and 
multiplied  by  the  scale  of  diagram,  will  give  the  mean  effective 


Fig.  205.    Diagram  from  a  condensing  engine. 

pressure.  A  quick  way  of  making  a  close  approximation  to  the 
mean  effective  pressure  of  a  diagram  is,  to  draw  line  a  6,  Fig.  206, 
touching  at  a,  and  so  that  space  d  will  equal  in  area  spaces  c  and 
e,  taken  together,  as  nearly  as  can  be  estimated  by  the  eye. 
Then  a  measure,/,  taken  at  the  middle,  will  be  the  mean  effective 
pressure.  With  a  little  practice,  verifying  the  results  with  the 
planimeter,  the  ability  can  soon  be  acquired  to  make  estimates  in 


HANDBOOK    ON    ENGINEERING. 


353 


this  way  with  only  a  fraction  of  a  pound  of  error  with  diagrams 
representing  some  degree  of  load.  With  very  high  initial  pres- 
sure and  early  cut-off,  it  is  not  so  available. 


a 


Fig.  206.    Mer nod  of  estimating  the  mean  pressure. 

The  indicated  horse-power.  — IHP  is  found  by  multiplying 
together  the  area  of  the  piston  (minus  half  the  area  of  the  piston- 
rod  section,  when  great  accuracy  is  desired),  the  mean  effective 
pressure  and  the  travel  of  the  piston  in  feet  per  minute,  and 
dividing  the  product  by  33,000.  It  is  sometimes  convenient  to 
know  the  HP  constant  of  an  engine,  which  is  the  HP  for  one 
revolution  at  one  pound  mean  effective  pressure.  This  multiplied 
by  the  mean  effective  pressure,  and  by  the  number  of  revolutions 
per  minute,  gives  the  IHP. 

THEORETICAL  CURVE. 

Testing  expansion  curves.  —  It  is  customary  to  assume  that 
steam,  in  expanding,  is  governed  by  what  is  known  as  Mariotte's 
law,  according  to  which  its  volume  and  pressure  are  inversely  pro- 

23 


354 


HANDBOOK    ON    ENGINEERING. 


portional  to  each  other.  Thus,  if  a  cubic  foot  of  steam  at,  say, 
100  pounds  pressure  be  expanded  to  2  cubic  feet,  its  pressure 
will  fall  to  50  pounds,  and  proportionately  for  all  other  degrees 
of  expansion.  The  pressures  named  are  lt  total  pressures  ;  "  that 
is,  they  are  reckoned  from  a  perfect  vacuum.  A  theoretic  ex- 
pansion curve  which  will  conform  to  the  above  theory  may  be 


\ 


\, 


\ 


s. 


10 


Fig.  207.    Locating  the  trne  expansion  curve. 

traced  by  the  following  method :  Referring  to  Fig.  207,  having 
drawn  the  clearance  and  vacuum  lines  as  before  explained,  draw 
any  convenient  number  of  vertical  lines,  1,  2,  3,  4,  5,  etc.,  at 
equal  distances  apart,  beginning  with  the  clearance  line  and  num- 
ber them  as  shown.  Decide  at  what  point  in  the  expansion  curve 


HANDBOOK    ON    ENGINEERING. 


of  the  diagram  we  desire  the  theoretic  curve  to  coincide  with  it. 
Suppose  we  choose  line  10,  on  which  we  find  the  indicated  pres- 
sure to  be  25  pounds.  Multiply  this  pressure  by  the  number  of 
the  line  (10)  and  divide  the  product  (250)  by  the  numbers  of 
each  of  the  other  lines  in  succession.  The  quotients  will  be  the 
pressures  to  be  set  off  in  the  lines.  Thus,  250  divided  by  9  gives 
27.7,  the  pressure  on  line  9  ;  and  so  for  all  the  others.  The 
same  curve  may  also  be  traced  by  several  geometric  methods,  one 
of  which  is  as  follows,  referring  to  Fig.  208  :  — 


E 


H 


Fig.  208.    Drawing  the  hyperbolic  curve. 

Having  drawn  the  clearance  and  vacuum  lines  as  before, 
select  the  desired  point  of  coincidence,  as  a,  from  which  draw  the 
perpendicular  a  A.  Draw  A  B  at  any  convenient  height  above  or 
near  the  top  of  the  diagram,  and  parallel  to  the  vacuum  line  D  C. 
From  A  draw  A  C  and  from  a  draw  a  b  parallel  to  D  (7,  and  from 


356  HANDBOOK    ON    ENGINEERING. 

its  intersection  with  A  B,  erect  the  perpendicular  b  c,  locating  the 
theoretical  point  of  cut-off  on  A  B.  From  any  convenient  num- 
ber of  points  in  A  B  (which  may  be  located  without  measurement) 
as  E,  F,  6r,  H,  draw  lines  to  (7,  and  also  drop  perpendiculars  E  e, 
Ff,  Gg,  Hli,  etc.  From  the  intersection  of  E  0  with  b  c,  draw  a 
horizontal  to  e,  and  the  same  for  each  of  the  other  lines  F  <7, 
G  (7,  H  C;  establishing  points  e,/,  #,  ft,  in  the  desired  curve. 
Any  desired  number  of  points  may  be  found  in  the  same  way. 
But  this  curve  does  not  correctly  represent  the  expansion  of 
steam.  It  would  do  so  if  the  steam  during  expansion  remained 
or  was  maintained  at  a  uniform  temperature ;  hence,  it  is  called 
the  isothermal  curve,  or  curve  of  same  temperature.  But,  in  fact, 
steam  and  all  other  elastic  fluids  fall  in  temperature  during  expan- 
sion, and  rise  during  compression  ;  and  this  change  of  temperature 
augments  the  change  of  pressure  slightly ;  so  that  if,  as  before 
assumed,  a  cubic  foot  of  steam  at  100  pounds  total  pressure  be 
expanded  to  two  cubic  feet,  the  temperature  will  fall  from  nearly 
328°  to  about  278°,  and  the  pressure  instead  of  falling  to  fifty 
pounds,  will  fall  a  trifle  below  48  pounds.  A  curve  in  which  the 
pressure  due  to  the  combined  effects  of  volume  and  resulting 
temperature  is  represented,  is  called  the  adiabatic  curve,  or  curve 
of  no  transmission  ;  since,  if  no  heat  is  transmitted  to  or  from  the 
fluid  during  change  of  volume,  its  sensible  temperature  will 
change  according  to  a  fixed  ratio,  which  will  be  the  same  for  the 
same  fluid  in  all  cases.  It  is  not  necessary  to  give  any  of  the 
usual  methods  of  tracing  the  adiabatic  curve,  since  the  isothermal 
curve  is  the  one  generally  used  for  that  purpose.  And  while  it  is 
incorrect  in  that  it  does  not  show  enough  change  of  pressure  for  a 
given  change  of  volume,  the  great  majority  of  actual  diagrams  are 
still  more  incorrect  in  the  same  direction ;  so  that  when  a  diagram 
conforms  to  it  as  closely  as  the  one  used  in  these  illustrations,  it 
is  considered  a  remarkably  good  one.  A  sufficiently  close 
approximation  to  the  adiabatic  curve  to  enable  the  non-profes- 


HANDBOOK    ON    ENGINEERING.  357 

sional  engineer  to  form  an  idea  of  the  difference  between  the  two, 
may  be  produced  by  the  following  process:  Taking  a  similar 
diagram  to  those  used  for  the  foregoing  illustrations,  we  fix  on  a 
point  A  near  the  terminal,  where  the  total  pressure  is  25  pounds. 
As  before,  this  point  is  chosen  in  order  that  the  two  curves  may 
coincide  at  that  point.  Any  other  point  might  have  been  chosen 
for  the  point  of  coincidence ;  but  a  point  in  that  vicinity  is  generally 
chosen  so  that  the  result  will  show  the  amount  of  power  that 
should  be  obtained  from  the  existing  terminal.  This  point  is  3.3 
inches  from  the  clearance  line,  and  the  volume  of  25  pounds  is 
996  ;  that  is,  steam  at  that  pressure  has  996  times  the  bulk  of 
water.  Now,  if  we  divide  the  distance  of  A  from  the  clearance 
line  by  996,  and  multiply  the  quotient  by  each  of  the  volumes  of 
the  other  pressures  indicated  by  similar  lines,  the  products  will  be 
the  respective  lengths  of  the  lines  measured  from  the  clearance 
line,  the  desired  curve  passing  through  their  other  ends.  Thus, 
the  quotient  of  the  first,  or  25-pound  pressure  line  divided  by 
996  is  .003313;  this  multiplied  by  726,  the  volume  of  25-pound 
pressure,  gives  2.4,  the  length  of  the  25-pound  pressure  line  ;  and 
so  on  for  all  the  rest. 

Fig*  209  shows  a  card  taken  from  a  Corliss  engine,  running  at  a 
speed  of  about  ninety  revolutions  per  minute.  On  account  of  the 
slow  speed  and  the  quick 
admission  obtained  by  this 
form  of  valve  gear,  but  lit- 
tle compression  is  needed. 
For  high  speed  engines, 
there  is  much  more  com- 
pression. At  high  speeds, 

the  expansion  line  of   the       _,      ....     ._ .  . 7: — r. 

Fig.  209.    Diagram  from  Corliss 

indicator  card,  instead  of  engine. 

being  a  smooth  curve  like  that  shown  in  Fig.  209 ,  is  of  ten  a  wavy 

line,  due  to  oscillations  of  the  spring  in  the  indicator. 


358  HANDBOOK    ON    ENGINEERING. 

Fig.  2  JO  represents  what  is  called  a  stroke  card.     The  indicator 

shows  us  the  pressure  on 
one  side  of  the  piston  for 
a  revolution.  When  we 
calculate  the  horse-power 
from  a  card,  we  are  as- 
suming that  the  back  pres- 
sure and  compression 
line  on  the  other  side  of 

"      "-  the  piston  are  the  same  as 

Fig.  210.    Showing  a  stroke  card.       shown  on  the  card.    This 

may  or  may  not  be  the  case.  In  calculating  the  total  horse-power 
for  the  two  ends  of  the  cylinder,  any  error  from  this  cause  affect- 
ing the  calculation  for  one  end  of  the  cylinder,  will  be  nearly 
balanced  by  an  opposite  error  in  the  calculations  for  the  other  end, 
so  that  the  final  result  is  practically  correct.  If  it  were  not  for 
the  piston-rod  making  the  area  of  one  side  of  the  piston  smaller 
than  on  the  other,  there  would  be  absolutely  no  error  arising 
from  this.  The  stroke  card  shows  the  pressure  on  opposite 
sides  of  the  piston  at  all  points  of  the  stroke.  The  difference 
between  the  lines  at  any  point  is  the  effective  push  per  square 
inch.  This  card  is  constructed  by  using  the  steam  and  expan- 
sion lines  of  the  card  from  one  end,  and  the  back  pressure 
and  compression  lines  for  the  same  stroke,  from  the  card  taken 
on  the  other  end.  In  constructing  diagrams  for  very  accurate 
work,  the  ratio  of  the  areas  of  the  two  sides  of  the  piston  have 
to  be  considered ;  the  pressure  above  the  atmosphere  for  one 
side  being  multiplied  by  this  ratio.  It  will  be  seen  that  up  to 
the  point  of  cut-off,  the  difference  of  pressure,  or  effective  pres- 
sure, is  nearly  constant ;  this  difference  grows  less,  due  to  the 
drop  along  the  expansion  curve,  till  at  the  point  where  the 
two  lines  cross,  the  pressure  on  the  two  sides  balances.  Be- 
yond this  point,  the  pressure  exerted  to  hold  the  piston  back 


HANDBOOK    ON    ENGINEERING. 


359 


Is  greater  than  that  exerted  to  push  it  ahead.  The  energy  stored  in 
the  fly-wheel  during  the  first  part  of  the  stroke  is  given  out  here 
near  the  end  of  the  stroke  to  help  the  engine  over  the  dead  point. 

STEAfl  CHEST  CARDS. 

By  attaching  one  indicator  to  the  steam  chest  of  an  engine, 
and  another  to  one  end  of  the  cylinder,  it  can  be  seen 
whether  the  pipes  and  ports  are  of  sufficient  size.  A 
sloping  steam  line  on  an  indicator  card  may  be  due  to  too 
small  a  steam  pipe,  or  too 
small  steam  ports',  or  to 
both  of  these  combined. 
This  does  not  apply,  of 
course,  to  engines  using 
throttling  governors. 

Fig»2n  shows  the  effect 
of  too  small  steam  pipe. 
When  steam  is  admitted 


Fig.  211.    Steam  chest  card  on 
forward  stroke. 


to  the  cylinder,  there  is  a 

drop   in   pressure   in   the 

chest.  This  drop  becomes  greater  in  amount  as  the  speed  of  the 

piston  increases.  At  cut- 
off, the  flow  of  steam  into 
the  cylinder  stops,  then 
the  pressure  in  the  chest 
reaches  boiler  pressure. 
If  there  is  no  great  drop 
in  the  line  on  the  steam 
chest  card,  and  a  consid- 
erable drop  in  the  steam 


Fig.  212.    Steam  chest  card  on 
forward  stroke. 


too  small. 


line  of  the  card,  it  would 
mean   that  the    ports  are 
Such  a  case  is  shown  by  Fig.  212. 


360 


HANDBOOK    ON    ENGINEERING. 


Fig.  213.    Steam  chest  card  on 
forward  stroke. 


If  there  is  a  drop  in 
the  chest  line  up  to  cut- 
off, and  a  still  greater 
drop  in  the  steam  line 
of  the  card,  it  would 
indicate  that  both  the 
steam  ports  and  the 
steam  pipe  were  too 
small.  Fig.  213  shows 
such  a  case. 


ECCENTRIC  OUT  OF  PLACE. 

Fi g*s*  214  to  2 \1  inclusive,  show  cards  taken  from  a  Corliss  en- 
gine having  the  eccentric  out  of  adjustment.  Similar  cards  would 
be  obtained  from  any  en- 
gine having  all  the  valves 
moved  by  one  eccentric. 
The  plain  slide  valve  and 
the  locomotive,  especially 
in  full  gear,  would  give 
similar  cards  for  the  same 
derangements  of  eccen- 
tric. 

Fig.  2*4  was  taken  with     Figg.  214  and  21g.    Effects  o( 
the  eccentric  a  trifle  less  Of  eccentric. 

than  90°  ahead  of  the  crank,  or  about  20°  behind  where  it  belongs 
on  this  particular  engine. 

Fig*2J5  shows  the  eccentric  moved  too  far  ahead  of  the  crank. 

By  comparison  with  Fig.  209,  it  will  be  seen  that  moving  the 
eccentric  back  makes  all  the  events  of  the  stroke,  such  as  admis- 
sion, release  and  compression  and  cut-off,  in  the  case  of  engines 
without  automatic  cut-off  governor,  come  later ;  while  moving 
the  eccentric  ahead  brings  these  events  earlier. 


HANDBOOK    ON    ENGINEERING. 


361 


Figs.  2J6  and  217  are  similar  to  Figs.  214  and  215,  the  only  dif- 
ference being  that  eccentric  is  moved  a  greater  distance  out  of  plane. 

In  Fig.  2 \6  the  admission 
is  very  late.  Release  does 
not  occur  until  after  the 
piston  has  started  on  the 
return  stroke,  the  steam, 
until  released,  being  com- 
pressed back  along  the  ex- 
pansion curve.  This  com- 

pression  is   always  a  trifle        ^  216  „„  M7>._  Eccentric 
below   the   expansion  line,  diagrams. 

due  to  the   fact   that  some  of   the  steam  has  condensed  in  the 
interval  between  the  end  of  the  stroke  and  the  release. 

Figf.  2J7  shows  too  much  compression  and  too  early  a  release. 
Steam  is  compressed  above  boiler  pressure  in  the  cylinder,  when 
the  valve  lifts  and  the  steam  escapes  into  the  chest. 

Cards  like  Figs.  214  and  215  are  very  common. 

ECCENTRIC  DIAGRAMS. 

As  small  distances  near  the  ends  of  the  indicator  cards  repre- 
sent a  large  angular  motion  of  the  crank,  the  events  occurring  at 
the  ends  of  the  card  are  so  squeezed  together  that  it  is  hard  to 
tell  from  the  card  just  what  any  peculiarity  in  the  lines  may  be 
due  to.  The  eccentric  rod  working  the  valves  of  the  engine  will 
be  moving  at  its  greatest  speed  when  the  crank  is  near  the  centers 
and  the  piston  near  the  ends  of  the  stroke ;  since  the  eccentric  is 
about  90°  ahead  of  the  crank.  If  the  motion  of  the  indicator 
drum  is  taken  from  the  eccentric  rod  instead  of  the  cross-head,  the 
card  will  be  changed  in  shape,  compression  and  release  coming 
near  the  middle  of  the  card ;  these  are  spread  out  over  consider- 
able length,  the  cut-off,  expansion  and  backpressure  lines  coming 
near  the  ends  of  the  card. 


362 


HANDBOOK    ON    ENGINEERING. 


Figf*2J8  gives  a  steam  card  drawn,  assuming  that  the  expansion 
and  compression  lines  are  hyperbolic.   The  eccentric  card  for  this 

has  been  plotted,  and  cor- 
responding points  marked 
with  the  same  letters.  The 


F  F 


Fig.  218.  Combined  diagram.  Fig.  219.    Ordinary  diagram. 

compression  curve,  extending  from  F  to  A,  is  a  double  curve. 
Admission  occurs  at  A,  cut-off  at  B,  release  at  (7,  and  compres- 
sion at  F. 

Figs*  2 19  and  220  show  cards  taken  from  an  engine  having  tight 
valves  and  a  tight  piston.     Corresponding  points  on  the  two  cards 

are  lettered  the  same.  For  a 
cut-off  later  than  half  stroke, 
the  steam  line  on  the  eccen- 
tric card  doubles  on  itself,  as 
shown  in  Figs.  220  and  222. 


The  peculiar  bend  shown 
by  the  dotted  lines  on  com- 


Fig.  220.    Eccentric  diagram. 

pression  curve  of  the  steam  card, 
Fig.  218,  is  developed  on  the 
eccentric  card  into  a  well  marked 
flat  place.  Evidently  this  rep- 
resents a  loss  of  pressure  at  this 
point,  which  may  be  attributed 
to  one  or  more  of  three  causes :  pig.  221.  Eccentric  diagram. 
first,  leakage  by  the  piston ; 
second,  leakage  by  the  exhaust  valves ;  third,  a  rapid  condensa- 


HANDBOOK    ON    ENGINEERING.  363 

tion  of  steam.  If  by  leakage,  it  is  probable  that  there  is  steam 
blowing  by  all  through  the  stroke. 
Near  the  end  of  the  stroke  the  pis- 
ton is  moving  at  so  slow  a  rate  that 
the  leakage  overbalances  the  com- 
pression. It  frequently  happens 
that  the  pressure  drops  off  at  the 

end  of  compression,  making  the  Fig.  222,  Eccentric  diagram. 
upper  end  of  the  compression  line 

resemble  an  inverted  letter  U.  If  the  leakage  is  by  the  piston, 
it  will  appear  or  may  be  made  to  appear  near  release,  as  will  be 
explained  later.  The  effect  of  compressing  steam  is  to  dry  it, 
or,  if  dry  already,  to  superheat  it.  While  it  may  be  possible  in 
some  cases  for  some  of  the  drop  here  to  be  due  to  condensation, 
in  the  majority  of  cases  leakage  is  the  trouble. 

Fig.  223  shows  the  effect  of  a  bad  leakage  by  the  piston.     This 
leakage  is  made  evident  by  the  appearance  of  the  upper  end  of 

the  compression  curve 
and  by  the  increase  in 
pressure  along  the  expan- 
sion line  just  before  re- 
lease. By  referring  to 
the  stroke  card,  it  will  be 
seen  that  near  this  point 

Fig.  223.    Effects  of  leakage.  *he  pressures  on  the  oppo- 

site side  of  the  piston  are 
the  greater,  so  that  the  leakage  is  now  into  the  side  on  which  the 
card  is  being  taken.  Unless  compression  on  one  side  conies 
earlier  than  release  on  the  other  side,  this  method  would  fail. 
In  most  engines  the  valves  are  set  so  that  compression  does 
come  earlier,  and  all  four  valve  engines  can  be  easily  set  so 
as  to  delay  release  on  one  end,  and  to  hasten  compression  on  the 
other  end.  In  the  case  of  a  Corliss  engine,  this  means  simply 


364 


HANDBOOK    ON    ENGINEERING* 


the  changing  the  length  of  the  rods  leading  from  the  wrist-plate 
to  the  valve  arm.  This  change  can  be  made  with  the  engine  run- 
ning. It  is  possible  that  a  card  like  Fig.  223  might  be  obtained 
from  a  four-valve  engine  having  a  leaky  steam  valve  on  one  end 
and  a  leaky  exhaust  valve  on  the  other  end. 

Fig*  224  represents  the  head  end  and  the  crank  end  cards 
taken  from  a  plain  slide  valve  engine.  The  valve  has  equal 
steam  lap  and  equal  exhaust  lap.  The  only  trouble  in  this  case 


Fig.  224.    Effects  of  changing  length  of  ralye  stem. 

is  that  the  valve  spindle  is  too  short.  Shortening  the  valve  spin- 
dle decreases  the  outside  lap  of  the  valve  and  increases  the  inside 
lap  for  the  head  end  side,  and  increases  the  outside  lap  and  de- 
creases the  inside  lap  for  the  crank  end  side.  As  will  be  seen  by 
the  cards,  the  head  end  has  the  cut-off  lengthened,  the  release 
delayed,  and  the  compression  hastened;  the  crank-end  has  the 
cut-off  shortened,  the  release  hastened,  and  the  compression  de- 
layed. If  the  valve  spindle  were  too  long  the  cards  shown  would 
be  interchanged,  the  crank  end  card  being  the  one  marked  head 
end. 

THE  STEAM  ENGINE  INDICATOR. 

Benefits  derived  and  information  ascertained  from  its  use*  — 
The  benefits  derived,  and  the  information  ascertained  from  the 
use  of  the  steam-engine  indicator  are  varied  and  important. 


HANDBOOK    ON    ENGINEERING.  365 

The  office  of  the  indicator  is  to  furnish  a  diagram  of  the 
action  of  the  steam  in  the  cylinder  of  an  engine  during  one  or 
more  revolutions  of  the  crank,  from  which  is  deduced  the  follow- 
ing data :  Initial  pressure  in  cylinder ;  piston  stroke  to  cut-off ; 
reduction  of  pressure  from  commencement  of  piston  stroke  to  cut- 
off ;  piston  stroke  to  release ;  terminal  pressure ;  gain  in  econ- 
omy due  expansion ;  counter  pressure,  if  engine  is  worked 
non-condensing ;  vacuum  as  realized  in  the  cylinder,  if  engine  is 
worked  condensing ;  piston  stroke  to  exhaust  closure,  usually 
reckoned  from  zero  point  of  stroke ;  value  of  cushion ;  effect  of 
lead  and  mean  effective  pressure  on  the  piston  during  complete 
stroke.  The  indicator  diagram,  when  taken  in  connection  with 
the  mean  area  and  stroke  of  piston  and  revolution  of  crank 
for  a  given  length  of  time,  enables  us  to  ascertain  the  power  de- 
veloped by  engine ;  and  when  taken  in  connection  with  the  mean 
area  of  piston,  piston  speed  and  ratio  of  cylinder  clearance, 
enables  us  to  ascertain  the  steam  accounted  for  by  the  indicator. 

The  mean  power  developed  by  engine  compared  with  the 
steam  delivered  by  boilers,  furnishes  cost  of  power  in  steam, 
and  when  compared  with  the  coal,  furnishes  cost  of  the  power  in 
fuel. 

The  diagram  also  enables  us  to  determine  with  precision  the 
size  of  steam  and  exhaust  ports  necessary,  under  given  conditions, 
to  equalize  the  valve  functions ;  to  measure  the  loss  of  pressure 
between  boiler  and  engine ;  to  measure  the  loss  of  vacuum  be- 
tween condenser  and  cylinder ;  to  determine  leaks  into  and  out 
of  the  cylinder ;  to  determine  relative  effects  of  jacketed  and 
un jacketed  cylinders ;  and  to  determine  effects  of  expansion  in 
one  cylinder,  and  in  two  or  more  cylinders. 

TO  TAKE  A  DIAGRAM. 

Connecting  cord*  —  The  indicator  should  be  connected  to  the 
engine  cross-head  by  as  short  a  length  of  cord  as  possible.     Cord 


366  HANDBOOK    ON    ENGINEERING. 

having  very  little  stretch,  such  as  accompanies  the  instrument, 
should  be  used ;  and  in  cases  of  very  long  lengths,  wire  should 
be  used.  The  short  piece  of  cord  connected  with  the  indicator  is 
furnished  with  a  hook ;  and  at  the  end  of  the  cord,  connected 
with  the  engine,  a  running  loop  can  be  made  by  means  of  the 
small  plate  sent  with  each  instrument ;  by  which  the  cord  can  be 
adjusted  to  the  proper  length,  and  lengthened  or  shortened  as 
required. 

Selecting  a  spring*  —  It  is  not  advisable  to  use  too  light  a 
spring  for  the  pressure.  Two  inches  are  sufficient  for  the  height 
of  diagram,  and  the  instrument  will  be  less  liable  to  damage  if 
the  proper  spring  is  used.  The  gauge  pressure  divided  by  2 
will  give  the  scale  of  spring  to  give  a  diagram  two  inches  high  at 
that  pressure. 

To  attach  a  card*  —  This  may  be  done  in  a  variety  of  ways, 
either  by  passing  the  ends  of  it  under  the  spring  clips,  or  by 
folding  one  end  under  the  left  clip,  and  bringing  the  other  end 
around  under  the  right;  but,  whatever  method  is  applied,  care 
should  be  taken  to  have  the  card  rest  smoothly  and  evenly  on  the 
paper  drum.  Now  attach  the  cord  from  the  reducing  motion  to 
the  engine  ;  but  be  certain  the  cord  is  of  the  proper  length,  so  as 
to  prevent  paper  drum  from  striking  the  inner  stop  in  drum 
movement  on  either  end  of  the  stroke. 

Tension  of  drum  spring*  —  The  tension  of  the  drum  spring 
should  be  adjusted  according  to  the  speed  of  the  engine ;  in- 
creasing for  quick  running,  and  loosening  for  slower  speeds. 

The  steam  should  not  be  allowed  into  the  indicator  until  it  has 
first  been  allowed  to  escape  through  the  relief  on  side  of  cock,  to 
see  if  is  clean  and  dry.  If  clean  and  dry,  allow  it  into  the  indi- 
cator, and  allow  piston  to  play  up  and  down  freely. 

After  taking  diagram,  turn  the  handle  of  cock  to  a  horizontal 
position,  so  as  to  shut  off  steam  from  piston,  and  apply  pencil  to 
the  paper  to  take  the  atmospheric  line. 


HANDBOOK    ON    ENGINEERING.  367 

In  applying  pencil  to  the  card,  always  use  the  horn-handle 
screw,  to  regulate  pressure  of  pencil  upon  paper  to  produce  as 
fine  a  line  as  possible.  After  the  atmospheric  line  is  taken,  turn 
on  steam,  and  press  the  pencil  against  card  during  one  revolution. 

When  the  load  is  varying,  and  the  average  horse-power  re- 
quired, it  is  better  to  allow  the  pencil  to  remain  during  a  number 
of  revolutions,  and  to  take  the  mean  effective  pressure  from  the 
average  of  the  several  diagrams. 


Fig.  225*    Diagram  from  a  Russell  engine. 

Fig.  225  was  taken  from  a  Russell  engine  13"  x  20",  running 
205  revolutions  per  minute,  boiler  pressure  98  Ibs.,  scale  of 
spring  60  Ibs.  Duty,  electric  lighting. 

After  sufficient  number  of  diagrams  have  been  taken,  remove 
the  piston,  spring,  etc.,  from  the  indicator,  while  it  is  still  upon 
the  cylinder ;  allow  the  steam  to  blow  for  a  moment  through  the 
indicator  cylinder ;  and  then  turn  attention  to  the  piston,  spring, 
and  all  movable  parts,  which  may  be  thoroughly  wiped,  oiled  and 
cleaned.  Particular  attention  should  be  paid  to  the  springs,  as 
their  accuracy  will  be  impaired  if  they  are  allowed  to  rust ;  and 
great  care  should  be  exercised  that  no  grit  or  substance  be  intro- 
duced to  cut  the  cylinder,  or  scratch  the  piston.  Be  careful 


368 


HANDBOOK    ON    ENGINEERING. 


always  not  to  bend  the  steel  bars  or  rods.  The  heat  of  the  steam 
blown  through  the  cylinder  of  the  indicator  will  be  found  to  have 
dried  it  perfectly,  and  the  instrument  may  be  put  together  with 
the  assurance  that  it  is  all  ready  for  use  when  required.  It  is  a 
saving  of  time  to  keep  indicator  in  order.  Any  engineer  can 
easily  perform  the  operation  without  further  instruction. 


Fig.  226.    Another  diagram  from  Russell  engine. 
Fig.  226  was  taken  from  a  Russell  engine  16"  x  24",  running 
157   revolutions   per   minute,    boiler  pressure  70  Ibs.,  scale   of 
spring  40  Ibs.     Duty,  flouring  mill. 


Fig.  227.    Friction  load.  Fig.  228.    Fail  load. 

HARRISBURG  IDEAL  SIMPLE  SINGLE  VALVE  ENGINE. 


HANDBOOK   ON    ENGINEERING. 


369 


Fig.  229.    Graduated  load.          Fig.  230.  Extreme  load  variation. 
HARRISBURG  IDEAL  SIMPLE  SINGLE  VALVE  ENGINES 


Fig.  231.    High  pressure  Fig.  232.    Low  pressure 

diagrams.  diagrams. 

HARRISBURG  IDEAL  COMPOUND  SINGLE  VALVE  ENGINE. 


Fig.  233.  Friction  diagrams.  Fig.  234.  Full  load  diagrams. 

HARRISBURG  STANDARD  SIMPLE  SINGLE  VALVE  ENGINE. 


370 


HANDBOOK    ON    ENGINEERING. 


Fig.  236.    Friction  load.  Fig.  236.    Full  load. 

HARRJSBURG  STANDARD  SIMPLE  FOUR-VALVE  ENGINE. 


Fig.  237.    High  pressure 
diagrams. 


Fig.  238.    Low  pressure 
diagrams. 


HARRISBUKG  STANDARD  COMPOUND  FOUR-VALVE  ENGINE. 


The  indicator  diagrams  from  Fig.  227  to  238  were  taken  from 
the  Harrisburg  Ideal  and  Standard  engines.  An  engineer  will 
see  from  these  cards  the  kind  of  card  he  should  get  from  a  high 
speed  engine  of  this  class. 

Fig*  239  is  from  a  Frick  Corliss  engine,  driving  a  Frick  com- 
pressor :  — 

Steam  Cylinder 19"x28". 

Steam    .    .. 95  Ibs. 

Revs.       .     ...     .     .     .  •  .     .     •  58 

Cond.  Press.  .     .     .     .     .     .     .     .  164  Ibs. 

Back  Press.  27   Ibs. 


HANDBOOK   ON    ENGINEERING. 


371 


Engine,  19"  x  28". 
Steam,  95  Ibs. 
Revs.  58  Ibs. 
Cond.  Press..  164  Ibs. 
Back  Press..  27  Ibs: 


Fig.  239.    Diagram  from  19"  x  28"  Eclipse  Corliss. 


INDICATOR  DIAGRAMS  FRONT  50-TON  "ECLIPSE" 
MACHINE. 


JR.  Hand  Ptimp* 
12*"  x  28". 
Scale.  120  //*. 


Fig.  240.    Diagram  from  right  hand  Eclipse  pump. 

Fig,  240  is  R.  Hand  Pump,     12£"  x  26",     Scale,  120  Ibs, 


372 


HANDBOOK    ON    ENGINEERING. 


\ 


L.-  Hand  Picmp. 

12J"  x  28". 
Scale,  J20M*. 


Fig.  241.    Diagram  from  left  hand  Eclipse  pump. 
Fig*  241  is  L.  Hand  Pump.     27|"  x  28".     Scale,  120  Ibs 


Engine,  80"  x  36" 
Steam,  75  /fo. 
Revs.  44 

Conrf.  /VMS.,  162 
Back  Press., 


Fig.  242.    Diagram  from  30"  x  36"  Eclipse  machine. 


Figs*  242   to   244,  are   diagrams  from  a  100-ton  "  Eclipse  " 
machine. 


HANDBOOK   ON    ENGINEERING.  373 

INDICATOR  DIAGRAMS  FROM  100-TON  "ECLIPSE" 
MACHINE. 


Fig.  243.    Diagram  from  right  hand  pump. 


Fig.  244.    Diagram  from  left  hand  pump. 


374 


HANDBOOK   ON   ENGINEERING. 


Fig.  245.    Diagrams  from  a  Ball  engine. 


HANDBOOK    ON    ENGINEERING. 

It  will  be  interesting  to  note  that  when  the  eccentric  is  simply 
moved  forward  or  backward  around  the  shaft  by  the  action  of  the 
governor,  all  the  events  of  the  stroke  —  admission,  release,  cut-off 
and  compression : —  will  be  hastened  or  retarded  together ;  but  if 
the  eccentric  be  so  designed  that  the  governor  will  shift  it  across 
the  shaft  instead  of  around  it,  the  admission  and  release  will  be 
effected  differently,  and  in  the  opposite  direction  from  the  cut-off 
and  compression.  If,  for  example,  the  cut-off  is  made  to  occur 
earlier  in  the  stroke,  the  compression  will  occur  earlier /also,  but 
the  admission  and  release  will  occur  later  instead  of  earlier.  By 
combining  the  two  movements  of  the  eccentric  and  having  the 
governor  move  it  partly  around  and  partly  across  the  shaft,  it  is 
possible  to  keep  the  admission  and  release  nearly  constant,  while 
the  cut-off  and  compression  vary.  This  result  is  attained  to  a 
certain  extent  in  the  best  single-valve  engines.  Besides  ttiese  two 
types,  there  are  numerous  other  styles  of  engines  in  wliich  the 
point  of  cut-off  is  varied  automatically.  Instead  of  a  shaft  gov- 
ernor with  a  shifting  eccentric,  a  weighted  pendulum  governor  is 
sometimes  employed  to  operate  the  link,  or  radius  rod  of  some 
one  of  the  various  link  motions.  Sometimes  there  are  separate 
admission  and  exhaust  valves,  the  former  being  under  the  con- 
trol of  a  shaft  governor,  and  the  latter  operated  by  a  fixed  eccen- 
tric, so  that  the  points  of  admission  and  cut-off  only  are  varied, 
while  the  points  of  release  and  compression,  which  depend  upon 
the  exfiaust  valve,  remain  fixed.  There  are  a  great  many  modifi- 
cations of  the  Corliss  engine,  as  originally  constructed  by 
Geo.  H.  Corliss,  and  there  are  many  engines  which,  while  not  re- 
sembling the  Corliss  engine,  have  some  arrangement  whereby  the 
cut-off  valves  are  tripped. 

On  pages  374  and  376  is  a  collection  of  diagrams,  which 
illustrate  very  nicely  the  peculiarities  and  difference  in  the  action 
of  throttling  and  automatic  engines.  The  four  diagrams  on 
page  374  were  taken  from  a  Ball  automatic,  in  an  electric  light 


376 


HANDBOOK   ON   ENGINEERING. 


Fig.  246.    Diagrams  from  a  Dickson  throttling  engine. 


HANDBOOK    ON    ENGINEERING.  377 


station.  The  first  diagram  was  taken  late  in  the  afternoon  when 
the  engine  was  started  and  before  any  load  was  thrown  on  to  the 
machine,  and  the  three  succeeding  cards  were  taken  at  intervals 
later  in  the  evening  as  the  number  of  lights  increased  and  the 
load  became  heavier.  Two  or  three  important  points  are  to  be 
noticed  in  connection  with  these  diagrams.  First,  the  initial 
pressure  of  the  steam  at  the  point  of  admission  is  very  nearly  the 
same  in  all  four  cards,  the  slight  variations  being  due  chiefly  to  a 
variation  in  the  boiler  pressure.  Second,  the  length  of  the  cut-off 
increases  with  the  load.  The  compression  also  becomes  later  as 
the  cut-off  lengthens,  and  while  there  is  also  a  change  in  the  points 
of  admission  and  release,  it  is  not  as  marked  as  the  changes  in  cut- 
off and  compression,  for  reasons  that  have  already  been  explained. 

Taking  the  cards  on  page  376,  we  have  four  excellent  examples 
of  the  action  of  a  throttling  engine.  These  cards  are  from  a 
Dickson  engine,  taken  at  the  same  station  and  under  the  same 
conditions  as  the  Ball  engine  cards,  with  the  exception  that  in 
this  case  both  head  and  crank-end  diagrams  were  taken  on  the 
same  cards,  while  only  the  head  end  diagrams  from  the  Ball 
engine  are  shown.  The  two  sets  of  diagrams  are  well  adapted 
for  comparison,  because  both  engines  are  of  the  single-valve  typej 
with  the  valve  moved  by  one  eccentric. 

The  points  to  be  noted  are,  first,  that  the  points  of  cut-off  are 
the  same,  namely  at  about  J  stroke,  in  all  the  throttling  cards, 
and  second,  that  the  power  of  the  engine  is  increased  by  the  action 
of  the  governor  in  opening  a  throttle  valve  wider,  allowing  steam 
to  enter  the  cylinder  at  higher  pressure. 

It  was  stated  at  the  outset  that  automatic  regulation  is  the 
most  approved  method  for  regulating  the  speed  of  steam  engines 
at  the  present  time.  It  is  generally  believed  and  it  is  probably 
true,  that  automatic  engines  give  better  economy  than  throttling 
engines  and  that  they  regulate  a  little  more  closely.  It  will 
readily  be  seen  that  when  the  governor  of  the  automatic  engine 


378  HANDBOOK    ON    ENGINEERING. 


changes  position,  it  measures  out  just  the  quantity  of  steam  that 
will  be  required  to  keep  the  engine  within  the  speed  limits  during 
the  following  stroke.  The  effect  of  this  regulation,  moreover,  is 
felt  at  one  point  in  the  stroke  only  —  the  point  of  cut-off  —  so  that 
any  change  in  the  governor  up  to  the  time  when  the  piston  nears 
the  point  of  cut-off  will  produce  an  immediate  change  in  the 
quantity  of  steam  admitted.  In  the  throttling  engine,  on  the 
other  hand,  the  regulation  is  effected  during  the  whole  stroke  up  to 
the  point  of  cut-off,  and  the  full  effect  of  any  change  of  the  gov- 
ernor cannot  be  felt  until  the  next  stroke.  With  regard  to  the 
relative  economy  of  the  two  types,  it  should  be  kept  in  mind  that 
the  throttling  engine  is  generally  of  cheap  construction,  has  large 
clearance,  a  single,  unbalanced  slide-valve  that  does  duty  for  both 
entering  and  exhaust  steam  and  aside  from  the  throttling  feature, 
is  inferior  to  the  average  automatic  engine.  It  is  reasonable  to 
suppose,  therefore,  that  at  least  a  part  of  the  large  steam  con- 
sumption generally  attributed  to  the  throttling  engine  is  due  to 
its  inferior  design  and  construction  and  not  to  its  method  of 
governing. 

For  example,  take  the  case  of  the  Ball  and  the  Dickson  engines, 
from  which  cards  are  shown.  They  both  have  a  single  slide- 
valve,  but  the  former  runs  at  higher  speed  than  the  latter  and  its 
valve  is  balanced,  so  that  for  these  reasons  it  would  be  expected 
to  be  a  little  more  economical.  We  should  not  expect,  however, 
that  a  test  would  show  any  decided  superiority  that  could  be 
attributed  to  the  method  of  governing.  If  we  were  to  compare 
the  average  throttling  engine  with  the  most  approved  type  of 
automatic  engine,  like  the  Corliss,  we  should  find  that  the  effi- 
ciency of  the  latter  was  much  higher.  The  gain,  however,  would 
be  due  to  a  large  extent  to  the  small  clearance  spaces,  separate 
steam  and  exhaust  valves,  and  other  important  features  of  the 
Corliss  engine,  rather  than  to  its  automatic  cut-off.  It  is  not 
the  purpose  to  discuss  here  why  these  features  give  improved 


HANDBOOK    ON    ENGINEERING.  379 

economy  over  the  single  valve,  but  simply  call  attention  to  the 
fact  that  they  exert  an  important  influence.  The  exact  influence, 
which  the  throttling  or  automatic  features  exert  apart  from  the 
general  constructive  features  of  the  engine  is  hard  to  determine. 
It  is  known  that  high-pressure  steam  is  more  economical  to  use 
than  low  pressure  steam  and  the  automatic  engine,  which  pre- 
serves nearly  the  boiler  pressure  up  to  the  point  of  cut-off,  gains 
on  this  account.  On  the  other  hand,  it  is  known  that  the  most 
economical  point  of  cut-off  for  a  non-condensing  engine  is  about 
one-third  stroke,  and  when  it  becomes  very  much  less  than  this 
there  is  a  serious  drop  in  the  economy.  A  very  short  cut-off 
with  high-pressure  steam  produces  so  great  a  variation  in  the 
temperature  during  one  stroke  of  the  piston  that  the  cylinder 
condensation  becomes  excessive.  For  very  light  loads,  therefore, 
it  would  be  better  to  throttle  the  steam  than  to  shorten  the  cut-off. 
It  is  necessary  for  all  engines  to  have  a  reserve  of  power  and 
hence  the  cut-off  of  throttling  engines  must  come  late  in  the 
stroke.  If  it  were  early  in  the  stroke,  there  would  not  be  enough 
reserve  power  with  the  reduction  in  the  pressure  of  the  steam  that 
is  necessary  with  this  type.  The  late  cut-off  produces  poor 
economy  when  the  load  is  heavy,  because  there  will  then  be  a 
high  terminal  pressure,  and  a  large  amount  of  heat,  corresponding 
to  this  pressure,  will  be  thrown  away.  A  throttling  engine  there- 
fore, may  be  expected  to  do  better  at  light  loads  than  at  heavy 
ones,  and  in  fact,  may  do  a  little  better  at  light  loads  than  the 
automatic  engine.  If  a  throttling  engine  could  be  run  so  as  not 
to  vary  much  from  its  most  economical  load,  and  could  be  de- 
signed to  have  the  good  features  of  the  best  automatic  engines, 
with  the  cut-off  at  an  earlier  period  in  the  stroke,  it  would  prob- 
ably be  nearly  or  quite  as  well  as  the  automatic  engine.  Under 
the  conditions  that  they  have  to  run,  however,  the  automatic  engine 
will  keep  the  lead,  although,  as  explained  above,  its  superiority 
is  not  due  entirely  to  the  automatic  feature. 


380  HANDBOOK   OF    ENGINEERING. 


CHAPTER    XV. 
ECONOMY  AND  OPERATION  OF  ENGINES. 

Engineers  over  the  country  have  been  discussing  whether  or 
not  more  steam  is  used  when  an  engine  is  made  to  run  faster  without 
changing  either  the  cut-off  or  the  back  pressure.  Some,  strange  as 
it  may  seem,  have  actually  held  to  the  opinion  that,  since  the  cut- 
off is  not  changed,  no  more  steam  is  used,  and  hence,  if  it  were 
possible  to  make  an  engine  run  faster  without  changing  the  cut-off, 
it  would  be  doing  more  work  than  before  without  any  increase  in 
the  consumption  of  steam.  Of  course,  this  is  wrong.  The  speed 
of  an  engine,  almost  any  engine,  may  easily  be  increased  without 
changing  the  cut-off,  and  when  this  is  done,  the  engine  will  do 
more  work  and  will  use  more  steam.  It  is  utterly  impossible  to 
get  something  for  nothing  out  of  a  steam-engine,  or  out  of  any 
engine  or  appliance.  The  only  way  in  which  a  steam-engine  can 
be  made  to  do  more  work  without  using  more  steam  is  to  increase 
its  efficiency.  And  when  everything  else  is  kept  the  same  and  the 
speed  only  of  an  engine  increased,  the  efficiency  is  very  slightly 
increased.  The  condensation  is  decreased  with  an  increase  of 
speed,  but  the  decrease  would  be  so  slight  for  most  cases  that  it 
would  hardly  be  worth  considering.  When  an  engine  is  cutting 
off  at  a  certain  part  of  the  stroke,  it  uses  at  every  stroke  a  cer- 
tain weight  of  steam  which  depends  upon  the  initial  pressure  of 
the  steam,  clearance  volume  of  the  engine  and  the  point  of  cut- 
off. If  the  engine  makes  400  strokes  per  minute  (200  revolu- 
tions, if  a  double  acting  engine)  the  weight  of  steam  used  will  be 


HANDBOOK   ON   ENGINEERING. 

400  times  the  weight  used  in  one  stroke ;  but  if  the  engine  be 
made  to  make  500  strokes  per  minute,  the  weight  of  steam  used 
per  minute  will  be,  neglecting  the  small  difference  in  condensa- 
tion, 500  times  the  weight  used  in  one  stroke. 

HOW  TO  INCREASE  THE  SPEED,  OR  INCREASE  THE  POWER 
OF  A  CORLISS  ENGINE. 

There  are  three  ways  in  which  this  can  be  done.  Take,  for 
example,  a  24"  x  48"  simple  Corliss  engine  making  70  revolu- 
tions per  minute,  the  boiler  gauge  pressure  80  Ibs.  per  square 
inch,  one-quarter  cut-off,  or  cut-off  12  inches  from  the  beginning 
of  the  stroke  ;  the  mean  effective  pressure,  say  about  42  Ibs.  per 
sq.  in.,  the  governor  pulley  on  the  main  shaft  10  inches  in  diam- 
eter, the  pulley  on  the  governor  shaft  7  in.  in  diameter,  and  the 
friction  of  engine,  cylinder  clearance,  condensation,  etc.,  left 
entirely  out  of  the  question.  It  is  desired  to  increase  the  speed 
of  this  engine  to  80  revolutions  per  minute,  and  in  this  manner 
increase  its  horse-power. 

First  method*  —  Regardless  of  piston  rod,  the  area  of  the  pis- 
ton is  452.4  square  inches,  nearly.  The  piston  speed  of  this 
engine  is  560  feet  per  minute,  and  its  horse-power  322,  nearly. 

452.4x42x560 

Thus: Qo/wm        ~  =322.     So  that  the  horse-power  of  this 

ooUUU 

engine  at  70  revolutions  per  minute  is  322,  nearly,  and  this  is 
what  the  manufacturer's  catalogue  gives.  Now,  in  order  to  get 
80  revolutions  per  minute,  take  the  7-inch  pulley  off  the  governor 
shaft,  and  put  in  its  place  an  8-inch  pulley.  Thus :  70 :  80 :  : 
7:8.  Then,  the  governor  balls  will  revolve  in  the  same  relative  • 
plane  that  they  did  before,  and  the  cut-off  will  remain  the  same ; 
that  is,  at  one-quarter,  or  12  in.  of  the  stroke.  Thus,  7:  10:: 
70 :  100.  And  8  :  10  :  :  80  :  100.  So  the  governor  balls  make  100 
revolutions  per  minute,  both  before  and  after  making  the  change. 


382  HANDBOOK    ON    ENGINEERING. 

Now,  with  the  engine  speeded  up  to  80  revolutions  per  minute, 
we  get  46  more  horse-power.     Thus:    Piston  speed  equals  640 

452.4x42x640 
feet    per   minute.     Then,       —  SSOCK)  -  =  ^^    horse-power, 

nearly.     And  368  minus  322  =46.     Now,  it  would  appear  that 
we  are  getting  46  horse-power  more  for  nothing,  but  such  is  not 

452.4x12x2x70 
the  case.     For,   -  VIZR  --  =439.8  +  ,    or    nearly    440 


cubic  ft.  of  steam   per  minute,   at  80  Ibs.   boiler  pressure,  are 

452.4x12x2x80 
required  to  develop  322  horse-power.     And, 


=  502.6+  or  nearly  503  cubic  ft.  of  steam  per  minute,  at  80 
Ibs.  boiler  pressure,  are  required  to  develop  368  horse-power. 
Then,  503  minus  440  =  63  cubic  feet  more  of  steam  at  80  Ibs. 
boiler  pressure,  which  means  more  water  evaporated  per  minute 
and  more  coal  burned  per  hour. 

Second  method*  —  Retain  the  same  engine  speed  and  the  same 
cut-off,  but  increase  the  boiler  pressure  from  80  to  90  Ibs.  Then 
80:  90:  :  42  :  47  +  ,  call  it  48  Ibs.  mean  effective  pressure. 

452.4x48x560 
Then,    -  SSOOQ  -  ==  ^^    horse-power,  nearly,  the  same  as 

before,  and  as  given  in  the  manufacturer's  catalogue.  We  are 
now  using  440  cubic  feet  of  steam  per  minute  at  90  Ibs.  pressure, 
with  an  increase  of  6  Ibs.  M.  E.  P.  ;  consequently,  more  coal  per 
hour  must  be  burned. 

Third  method*  —  Retain  the  same  boiler  pressure,  that  is  80 
Ibs.,  and  weight  the  governor  so  as  to  make  the  balls  revolve  in  a 
lower  plane  in  order  to  give  a  later  cut-off.  Thus,  322  :  368  :: 
J:f.  That  is,  the  cut-off  must  take  place  at  about  %  of  the 
stroke  instead  of  at  J.  Then,  J:f::42:48.  That  is  the 
M.  E.  P.  will  be  48  Ibs.  per  square  inch  with  a  cut-off  at  %  of  the 

452.4x48x560 
stroke.    Then,  -  33000  -  ==  ^68  horse-power,  the  same  as 


HANDBOOK    ON    ENGINEERING.  383 

before.  But,  %  of  48  =  13f ,  or  13.71  inches  nearly,  so  that, 
instead  of  cutting  off  at  12  inches  with  80  Ibs.  boiler  pressure, 
we  are  cutting  off  at  13.71  inches  and  using  63  cubic  feet  more 

452.4  x  13. 71x  2x70 

steam  per  minute.     Thus, =  503,    nearly. 

1728 

And,  503  minus  440=63,  that  is,  we  must  use  63  cubic  feet 
more  of  steam  per  minute  at  80  Ibs.  boiler  pressure,  in  order  to 
get  46  more  horse-power,  which  means  the  evaporation  of  more 
water  per  minute,  and  the  burning  of  more  coal  per  hour. 


HOW    TO   INCREASE    THE    HORSE-POWER    OF    AN    ENGINE 
HAVING  A  THROTTLING  GOVERNOR. 

There  are  three  ways  in  which  this  can  be  done,  also.  We 
will  take,  for  example,  a  plain  slide-valve  engine  10  x  16  inches, 
making  150  re  volutions  per  minute,  with  T9^  cut-off,  and  M.  E.  P. 
say  31£  Ibs.  per  square  inch,  with  a  boiler  pressure  of  60  Ibs. 
by  gauge.  The  governor  pulley  on  the  main  shaft  6  inches 
in  diameter,  and  the  pulley  on  the  governor  shaft  4  inches 
in  diameter.  The  horse-power  of  this  engine  is  about  30. 

Thus,    16x2  =  2f  ft.,  and  150  x  2|  =  400  ft.,  the  piston  speed. 
\a 

10  x  10  x. 7854x31.5x400  =       horse_power,  nearly. 

33000 

It  is  now  desired  to  run  the  engine  at  180  revolutions  per 
minute  in  order  to  develop  6  horse-power  more.  In  order  to 
obtain  these  results,  the  governor  pulley  must  be  enlarged,  so  as 
to  make  the  governor  balls  revolve  in  the  same  plane  at  180  revo- 
lutions per  minute,  that  they  now  do  at  150  revolutions.  Thus, 
4:6::  150:  225,  that  is,  the  governor  balls  are  now  making 
225  revolutions  per  minute.  And  150 :  180  : :  4 :  4.8.  Con- 
sequently, the  governor  pulley  must  be  increased  to  4.8  inches  in 


384  HANDBOOK   ON    ENGINEERING. 

diameter.  Then,  4.8 :  6  : :  180 :  225,  that  is,  the  governor  balls, 
after  the  change,  making  the  same  number  of  revolutions  as 
before.  At  18J3  revolutions  per  minute,  the  piston  speed  is  480 

feet    per    minute.     Thus,  =  21.     And,   180  x  2|  =  480. 

12 

Then,   78>54^3Q1^x480^  36  horse-power,  nearly.      It    might 

seem  from  the  above  that  we  are  getting  6  horse-power  more  for 
nothing ;  but  such  is  not  the  case.  For,  cutting  off  at  T9F  is 
equivalent  to  cutting  off  at  9  inches  of  the  stroke. 

™          78.54x9x2x150 

Then,  _          _ _  =  123  cubic  ft.,  nearly. 

1728 

78.54x9x2x180 

—  — 147  cubic    feet,    nearly.     And, 


1728 

147  minus  123  —  24.  So  that  for  6  horse-power  more,  we  are 
using  24  cubic  feet  more  of  steam  per  minute,  at  31.5  Ibs.  M.  E.  P. , 
which  means  more  water  evaporated  per  minute  and  more  coal 
burned  per  hour. 

If  the  boiler  pressure  may  be  safely  increased,  we  can  get  6 
horse-power  more  out  of  the  engine  without  increasing  its  speed, 
by  running  the  boiler  pressure  up  to  75  Ibs.  by  gauge.  Thus  75 
Ibs.  boiler  pressure  would  give  about  37.8  Ibs.  M.  E.  P.  with  T9^ 

cut-off.     Then,    ^8. 54  x  37.8  x  400  =  36  horse_power  nearly. 

33000 

In  this  case  no  change  should  be  made  in  the  governor,  nor  in 
the  speed  of  the  engine.  We  can  also  get  6  horse-power  more 
out  of  this  engine  by  cutting  off  later,  say  at  |,  in  order  to  get 
37.8  Ibs.  M.  E.  P.  But  a  later  cut-off  is  not  desirable,  because 
it  is  not  economical  of  steam,  and  besides,  it  would  require  a  new 
valve,  new  eccentric,  or  a  change  in  the  length  of  a  rocker  arm,  if 
not  a  change  of  the  valve-seat,  because  the  travel  of  the  valve 
would  have  to  be  increased. 


HANDBOOK   ON   ENGINEERING.  385 

HOW    TO    INCREASE  THE  HORSE-POWER    OF    AN    ENGINE 
HAVING  A  SHAFT  GOVERNOR. 

Suppose  it  is  desired  to  increase  the  speed  of  the  engine  from  250 
to  275  revolutions  per  minute,  cutting  off  at  i  stroke.  In  this 
case  the  governor  springs  should  be  so  adjusted  that  the  throw  of 
the  eccentric  will  be  the  same  at  275  revolutions  that  it  was  at  250 
revolutions.  This  will  require  an  increased  consumption  of  steam 
per  minute  at  the  same  initial  cylinder  pressure  as  before  making 
the  change,  consequently  more  fuel  will  be  required.  If  the  speed 
of  the  engine  is  not  to  be  changed,  an  increase  of  the  horse-power 
may  be  obtained  by  increasing  the  initial  cylinder  pressure,  if  the 
condition  of  the  boiler  will  so  permit.  Or,  the  initial  cylinder 
pressure  may  remain  unchanged  and  the  governor  springs  and 
levers  so  adjusted  as  to  give  a  later  cut-off,  say  at  |^  or  T7^  of  the 
stroke,  or  whatever  may  be  required  to  offset  the  increased  per- 
manent load,  the  speed  of  the  engine  remaining  unchanged.  Any 
one  of  the  changes  above  described  would  necessitate  an  increased 
consumption  of  fuel. 

HOW  TO  LINE  THE  ENGINE  WITH   A    SHAFT  PLACED    AT  A 
HIGHER  OR  A   LOWER  LEVEL. 

We  will  suppose  the  latter  shaft  not  yet  in  place,  but  to  be 
represented  by  a  line  tightly  drawn.  From  two  points  as  far 
apart  as  practicable,  drop  plumb  lines  nearly,  but  not  quite, 
touching  this  line.  Then  by  these  strain  another  line  parallel 
with  the  first,  and  at  the  same  level  as  the  center  line  of 
the  engine,  and  at  right  angles  with  this  stretch  another  represent- 
ing this  center  line,  and  extend  both  each  way  to  permanent  walls 
on  which  their  terminations,  when  finally  located,  should  be  care- 
fully marked,  so  they  can  at  any  time  be  reset.  The  problem  is 
to  get  the  latter  line  exactly  at  right  angles  with  the  former. 
Everything  depends  upon  the  accuracy  with  which  this  right 

25 


386 


HANDBOOK   ON    ENGINEERING. 


angle  is  determined.  It  is  done  by  the  method  of  right-angle 
triangles.  There  are  two  ways  of  applying  this  method.  In  the 
first,  one  end  of  a  measuring  line  is  attached  to  some  point  of 
line  No.  1,  and  its  other  end  is  taken  successively  to  points  on 
line  No.  2  on  opposite  sides  of  the  intersection,  as  illustrated  in 
the  following  figure,  in  which  A  B  is  a  portion  of  line  No.  1,  and 
C  D  of  line  No.  2,  the  direction  of  which  is  to  be  determined,, 
B  F  and  B  G  are  the  same  measuring  line  fixed  at  B,  and  applied 
to  the  line  C  D  successively  at  the  points  F  and  G.  The  dis- 


Fig.  247.    Lining  engine  with  line  shafting. 

tances  B  F  and  B  G  being,  therefore,  the  same,  when  E  F  is 
equal  to  E  G,  the  lines  A  B  and  C  D  are  at  right  angles  with  each 
other.  In  the  second,  application  is  made  of  the  law  that  the  square 
of  the  hypothenuse  of  a  right-angle  triangle  is  equal  to  the  sum 
of  the  squares  of  the  other  two  sides.  Thus  32  -j-  42  =  52.  So  if 
the  above  figure  E  B  =  4,  E  F=3,  and  B  F=6,  the  angle  at 
E  is  a  right-angle.  Any  unit  of  measure  may  be  used,  a  foot  is 
generally  the  convenient  one ;  so  any  multiple  of  these  numbers 
may  be  taken;  as,  for  example,  6,  8  and  10.  Respecting  the 
comparative  advantages  of  these  two  ways,  the  situation  will  of  ten 
determine  which  is  to  be  preferred.  In  the  former,  the  diagonal 


HANDBOOK   ON    ENGINEERING.  387 

being  the  same  line,  fixed  at  B  and  brought  successively  to  the 
points  F  and  6?,  its  length  is  immaterial,  though  generally  the 
longer  the  better ;  and  the  only  point  to  be  determined  is  the 
equality  of  E  F  and  E  G,  which  may  be  compared  with  each 
other  by  marks  on  a  rod.  In  the  latter,  the  proportionate 
lengths,  3,  4  and  5,  or  their  multiples,  must  be  exactly  measured. 
It  is  better  adapted  to  places  where  a  floor  is  laid  and  the  meas- 
urements can  be  transferred  by  trammels.  The  result  should  be 
verified  by  repeating  the  operation  on  the  opposite  side  of  the 
intersection  at  E,  and  when  so  verified  we  have,  in  fact,  the  first 
process,  without  the  additional  and  unnecessary  trouble  of  deter- 
mining the  relative  lengths  of  the  lines.  Care  should  be  taken 
when  a  measuring  line  is  used,  to  avoid  errors  from  its  elasticity „ 
On  this  account,  a  rod  is  often  employed.  Points  on  the  lines 
are  best  marked  by  tying  on  a  white  thread. 

HOW  TO  LINE  THE  ENGINE  WITH  A  SHAFT  TO  WHICH  IT  IS 
TO  BE  COUPLED  DIRECT. 

In  this  case,  it  is  supposed  that  the  engine  bed  and  the  bear- 
ings for  the  shaft  are  already  approximately  in  position.  They 
are  leveled  by  a  parallel  straight  edge  and  a  spirit  level.  To  line 
them  horizontally,  a  line  must  be  run  through  the  whole  series  of 
bearings  and  continued  to  a  permanent  wall  at  each  end,  and  its 
terminating  points,  when  determined,  carefully  marked,  as  already 
directed.  A  piece  of  wood  is  tightly  set  in  each  end  of  each 
bearing  and  the  surfaces  of  these  are  painted  white  or  chalked. 
Then  the  middle  of  each  piece  being  found  by  the  compasses,  two 
fine  lines  are  drawn  across  it,  equally  distant  from  the  middle,  and 
having  between  them  a  space  a  little  wider  than  the  thickness  of 
the  line.  The  line  being  tightened,  nearly  touching  the  blocks, 
or,  if  long,  having  its  sag  supported  by  them,  the  two  marks  on 
each  block  must  be  seen,  one  on  each  side  of  the  line,  with  the 
line  of  white  between. 


388  HANDBOOK    ON    ENGINEERING. 

HOW  TO  SET  A  SLIDE  VALVE  IN  A  HURRY. 

Open  the  cylinder  cocks;  then  open  the  throttle  slightly,  so 
as  to  admit  a  small  amount  of  steam  to  the  steam-chest.  Roll 
the  eccentric  forward  in  the  direction  the  engine  runs,  until  steam 
escapes  from  the  cylinder  cock  at  the  end  where  the  valve  should 
begin  to  open.  Now  screw  the  eccentric  fast  to  the  shaft.  Roll 
the  crank  to  the  next  center  and  ascertain  if  steam  escapes  at  the 
same  point,  at  the  opposite  end  of  the  cylinder.  If  so,  ring  the 
bell  and  go  ahead.  The  valve  gear  can  be  run  until  an  oppor- 
tunity occurs  to  remove  cover  from  steam-chest  and  examine  the 
valve. 

DO  YOU  DO  THESE  THINGS? 

A  writer  in  a  magazine  asks  and  answers  the  following 
pertinent  questions :  — 

Do  you  take  a  squirt-can  in  one  hand  and  project  a  stream  of 
oil  as  far  as  you  can  throw  it,  in  order  to  save  going  to  the  oil 
hole  itself  ? 

If  you  do,  don't  do  it  any  more ;  willful  waste  is  downright 
robbery. 

Do  you  use  an  oil  can  at  all  for  oiling,  except  on  emergency,  or 
for  the  moment  ? 

If  you  do,  don't  do  it  any  more,  for  much  better  lubrication 
can  be  had  by  automatic  apparatus. 

Do  you  keep  an  old  tin  coffee-pot  full  of  suet  on  the  steam- 
chest,  and  every  time  you  have  nothing  else  to  do,  pour  a  dipper- 
f  ul  into  the  steam-chest  ? 

If  you  do,  stop  it  and  get  a  sight-feed  cup,  which  will  save 
you  the  labor  of  slushing  the  cylinder  and  save  the  cylinder  and 
valve-seats,  the  piston  and  follower,  and  all  other  places  touched 
by  the  grease. 


HANDBOOK    ON    ENGINEERING.  389 

Do  you  feed  the  boiler  until  the  water  is  out  of  sight  in  the 
glass,  then  shut  off  the  feed,  put  in  a  big  fire  and  sit  down  in 
a  dark  corner  with  a  four-horse  brier  pipe  and  smoke,  until  you 
happen  to  think  that  maybe- the  water  is  low? 

If  you  do  these  things  you  should  notify  the  coroner  that  some 
day  his  services  will  be  needed,  but  it  is  better  to  cease  the  prac- 
tice mentioned  before  the  coroner  comes. 

Do  you  stop  leaks  about  the  boiler  as  fast  as  they  occur,  or  do 
you  wait  until  the  places  sound  like  a  snake's  den  before  you  stir? 

If  you  do,  you  waste  heat,  which  is  the  same  word  as  money, 
only  differently  spelled.  Every  jet  of  hot  water  leaking  from  a 
steam  boiler  is  just  so  much  money  thrown  away,  and  if  it  was 
your  money  you  would  be  bankrupt  in  a  short  time,  in  some 
boiler  rooms. 

Do  you  take  a  screw  wrench  and  yank  away  at  a  bolt  or  nut 
under  steam  pressure? 

If  you  do,  there  will  come  a  time,  sooner  or  later,  when  you 
will  do  so  once  too  often,  and  either  kill  yourself  or  some  one  else. 
Bolts  and  nuts  are  liable  to  strip  or  break  if  tampered  with  under 
pressure,  and  they  never  tell  any  one  beforehand  when  they  are 
going  to  do  it. 

Do  you  attempt  to  stop  pounding  in  the  engine  by  laying  for 
the  crank-pin  as  it  comes  round,  and  trying  to  hit  the  key  once  in 
a  while  ? 

If  you  do,  ask  the  strap  and  neck  of  the  connecting-rod  how 
he  likes  it,  when  you  don't  hit  the  key  and  do  hit  the  oil  cup? 

Do  you  pack  the  piston  by  taking  it  out  of  the  cylinder,  lay- 
ing it  on  the  floor,  setting  out  the  rings,  and  then  when  the  piston 
will  not  go  into  the  cylinder,  try  to  batter  it  in  with  a  four-foot 
stick  of  cord  wood? 

If  you  do,  you  should  reform,  and  pack  the  piston  in  the 
cylinder  where  it  belongs,  being  sure  to  get  it  central  by  meas- 
uring from  the  lathe  center  in  the  end  of  the  piston  rod. 


390 


HANDBOOK    ON    ENGINEERING. 


Do  you  put  a  new  turn  of  packing  on  top  of  the  old,  hard- 
burned  stuff  when  the  piston  rod  leaks  steam  ? 

If  you  do,  you  will  have  a  scored  piston  rod  and  broken  gland 
bolts  some  day.  Packing  under  heat  and  pressure  gets  so  hard 
that  it  cuts  like  a  file  when  left  in  the  stuffing-box,  and  as  one 
begins  to  leak  all  the  old  stuff  should  be  pulled  out  and  new  put 
in  its  place. 

THE    TRAVEL    OF    A    SLIDE   VALVE. 


Figs.  248  and  249.    The  throw  of  the  eccentric. 

The  travel  of  a  slide  valve  is  found  as  follows :  The  maximum 
port  opening  at  the  head  end,  plus  the  maximum  port  opening  at 
the  crank  end,  plus  the  lap  at  the  head  end,  plus  the  lap  at  the 
crank  end.  Therefore,  If"  +  If"  +  f"  +  f"=4J",  the  re- 
quired travel  of  valve.  Incidentally,  it  may  be  well  to  mention 
that  the  travel  of  a  valve  may  also  be  obtained  from  the  eccentric, 
by  subtracting  the  thin  part  of  the  eccentric  from  the  thick 
part  as  per  Fig.  248,  or  again,  by  taking  twice  the  distance  between 
the  center  of  rotation  and  center  of  the  eccentric.  This  distance 
on  the  eccentric  is  the  end  valve  travel,  and  is  termed  the  c  G  throw  ' ' 
of  the  eccentric.  In  the  above  question,  the  travel  may  also  be 


HANDBOOK    ON    ENGINEERING. 


391 


found  by  the  aid  of  the  diagram,  Fig.  249,  which  is  explained  as 
follows:  From  the  center^.,  with  a  radius  of  £  inch  (lap), 
describe  a  circle  BCD.  From  any  point  in  the  circumference, 
say  B,  lay  off  the  distance  B  E  equal  to  the  maximum  port  open- 
ing, If"  ;  from  the  center  A,  with  a  radius  A  E,  describe  the 
circle  E  F  G;  the  diameter  of  the  circle  E  F  G  is  equal  to  the 
travel  of  the  valve,  which  is  4J".  Let  the  reader  try  this  with 
another  set  of  figures,  to  prove  the  correctness  of  the  diagram. 

LOSS  OF  HEAT  FROM  UNCOVERED   STEAM  PIPES. 

The  following  table  shows  the  loss  of  heat  through  naked  sfceam 
pipes,  wrought  iron,  of  standard  sizes.  The  best  covering  for  a 
steam  pipe  is  hair  felt  from  one  to  two  inches  thick,  depending  on 
the  diameter  of  the  pipe,  say  one  inch  thick  for  pipe  from  1  to  4 
inches  in  diameter,  and  two  inches  or  more  for  larger  pipes. 
Such  covering  will  save  at  least  96  per  cent.  Cheaper  coverings 
will  save  from  75  to  90  per  cent.  The  chief  value  of  the  table  is 
as  an  aid  in  estimating  the  saving  that  can  be  made  by  covering 
the  pipe.  The  money  loss  by  naked  pipe  being  known,  the  sav- 
ing can  be  estimated  and  the  cost  of  the  covering  will  decide  its 
value  as  an  investment. 

TABLE    OF    MONEY    LOSS  FROM    100    FEET  OF  NAKED  STEAM  PIPE,  FOB 
ONE    YEAR    OF    3000    WORKING  HOURS.    . 


•335. 

STEAM  PRESSURES. 

||t| 

50 

60 

70 

80 

90 

100 

fc-oo.2 

Ibs. 

Ibs. 

Ibs. 

Ibs. 

Ibs. 

Ibs. 

1 

$13.15 

$13.70 

$14.20 

$14.66 

$15.08 

$15.47 

H 

16.58 

17.29 

,  17.92 

18.49 

19.02 

19.51 

\L 

18.98 

19.78 

20.51 

21.17 

21.77 

22.33 

2 

23.72 

24.73 

25.63 

26.45 

27.21 

27.91 

2£ 

28.72 

29.94 

31.03 

32.03 

32.94 

33.79 

3 

34.97 

36.45 

37.78 

38.99 

40.10 

41.14 

4 

44.93 

46.86 

48.57 

50.13 

51.56 

52.89 

5 

55.57 

57.92 

60.04 

61.96 

63.73 

65.38 

6 

66.27 

69.08 

71.60 

73.89 

76.01 

77.96 

392  HANDBOOK   ON   ENGINEERING. 

RULES    AND    PROBLEMS    APPERTAINING    TO    THE    STEAM 

ENGINE. 

To  find  the  H.  P.  of  a  simple  non-condensing  engine :  — 

Rule*  —  Multiply  the  net  area  of  the  piston  in  square  inches, 
by  the  mean  effective  pressure  in  pounds  per  square  inch,  and  by 
the  velocity  of  the  piston  in  feet  per  minute,  and  divide  the  last 
product  by  33,000.  The  quotient  will  be  the  gross  H.  P.  Sub- 
tract from  this  from  ten  to  twenty  per  cent  for  friction  in  the 
engine  itself,  and  the  remainder  will  be  the  delivered  H.  P. 

Example*  —  The  area  of  the  piston  is  500  sqr.  ins.  Half  the 
area  of  the  piston-rod  is  5  sqr.  ins.  The  M.  E.  P.  is  50  Ibs. 
per  sqr.  in.  The  stroke  is  3  feet,  and  the  revolutions  per  minute 
125.  The  friction  is  10  per  cent.  What  is  the  delivered  H.  P. 
of  the  engine?  Ans.  506.25  H.  P. 

Operation* —  3  ft.  X  2  =  6  ft.  twice  the  stroke. 

Then,  500  —  5  =  495  sqr0  ins.  net  area  of  piston. 

And,  125  X  6  =  750  ft.  the  piston  speed  per  minute. 

And, =^562.5. 

33,000 

Then,  562.5  X  -90  =  506.25.     The  delivered  H.  P. 

For  a  condensing  engine :  — Add  the  vacuum  to  the  M.  E.  P. 
and  proceed  as  above. 

The  M.  E.  P.  is  the  average  pressure  in  the  cylinder,  less  the 
back  pressure. 

To  find  the  H.  P.  of  a  compound  noncondensing  engine :  — 

The  usual  method  of  calculating  the  H.  P.  of  a  multiple  cyl- 
inder engine  is  to  assume  that  all  the  work  is  done  in  the  low 
pressure  cylinder  alone,  and  that  such  a  M.  E.  P.  is  obtained  in 
that  cylinder  as  will  give  the  same  H.  P.  as  is  given  by  the  whole 
engine. 

Rule* — Find  the  ratio  of  areas  of  the  high  and  low  pressure 
cylinders, —  when  of  the  same  stroke,  as  they  usually  are, —  and 


HANDBOOK   ON    ENGINEERING.  393 

multiply  it  by  the  number  of  expansions  in  the  high  pressure 
cylinder,  for  the  total  number  of  expansions  in  both  cylinders. 
Find  the  hyperbolic  logarithm  corresponding  to  this  result  and 
add  1  to  it,  and  divide  the  sum  by  the  total  number  of  expan- 
sions. Multiply  this  result  by  the  absolute  steam  pressure,  and 
subtract  the  back  pressure.  Subtract  again  the  loss  in  pressure 
between  cylinders,  and  the  remainder  will  be  the  M.  E.  P.  Then 
multiply  the  net  area  of  the  low  pressure  cylinder  by  this  M.  E.  P. 
and  by  the  piston  speed  in  feet  per  minute  and  divide  by  33,000. 
Deduct  the  friction  in  the  engine  itself  and  the  remainder  will  be 
the  delivered  H.  P. 

Example*  —  Given  a  tandem  compound  engine  with  cylinders 
20"  and  32"  diameter,  and  4  feet  stroke,  making  75  revolutions 
per  minute,  boiler  gauge  pressure  125  Ibs.  per  sqr.  in.,  J  cut-off 
in  high  pressure  cylinder,  back  pressure  15J  Ibs.  per  sqr.  in., 
drop  in  pressure  between  cylinders  15  per  cent,  and  friction  in 
engine  10  per  cent.  What  is  the  H.  P.  delivered  of  this  engine? 
Ans.  338.4  H.  P. 

Operation*  —  Neglecting  the  areas  of  the  piston  rods,  we 
have :  — 

20  X  20  X  .7854  —  314.16  sqr.  ins.  area  of  high  pressure 
cylinder. 

And,  32  X  32  x  .7854  =  804,2  sqr.  ins.  area  of  low  pressure 
cylinder. 

Then,  804.2  -f-  314.16  =2.56  =  the  ratio  between  cylinders. 

And,  2.56  X  4  =  10.24  =  the  total  number  of  expansions. 
The  hyperbolic  logarithm  of  10.24  =  2.328.  (Seetableonp.  892.) 

And,  1  +  2.328  =  3.328. 

Then,  3.328  ~  10.24  =  .325. 

Also,  125  +  15  =  140  Ibs.,  the  absolute  pressure. 

And,  .325  X  140  =45.5  Ibs.,  forward  pressure. 

And,  45.5  —  15.25  =  30.25  Ibs.,  the  M.  E.  P. 


. 

394  HANDBOOK  ON  ENGINEERING. 

And,    30.25  X  .85^25.7    Ibs.  =the    M.    E.    P.    less    the 
44  drop." 

Then,  804.2  X25.7X8X75_  p> 

33,000 

And,  376  X  .90  =  338.4  H.  P.  delivered. 

For  a  compound  condensing  engine,  proceed  as  above,  except 
that  the  condenser  pressure,  due  to  impaired  vacuum,  only  should 
be  subtracted  from  the  forward  pressure. 

To  find  the  linear  expansion  of  a  wrought-iron  pipe  or  bar  :  — 

Rule,  —  Multiply  the  length  of  the  pipe  or  bar  in  indies  by 
the  increase  in  temperature,  and  by  the  constant  number  .0007, 
and  divide  the  last  product  by  100. 

Example*  —  Given  a  6-inch  wrought-iron  pipe  75  feet  long. 
Steam  pressure  150  Ibs.  by  gauge.  Temperature  of  pipe  when 
put  up  60  degs.  Fah.  What  is  its  linear  expansion?  Ans. 
2  ins.  nearly. 

Operation*  —  The  diameter  of  the  pipe  is  immaterial. 

Then,  150  Ibs.  pressure  =  366  degs. 

And,  366  —  60  •=  306  degs. 

Also,  75  X  12  =  900  inches  length  of  pipe. 


Then,  '  ^1.9278  inch. 

For  copper,  use  the  constant  number  .0009  ;  for  brass,  use 
.00107  ;  for  fire-brick,  use  .0003,  and  proceed  as  above. 

To  find  the  proper  diameter  of  steam  pipe  for  an  engine  :  — 

The  velocity  of  steam  flowing  to  an  engine  should  not  exceed 
6,000  feet  per  minute. 

Rule.  —  Multiply  the  area  of  the~piston  in  square  inches  by  the 
piston  speed  in  feet  per  minute,  and  divide  by  6,000  ;  and  divide 
again  by  .7854,  and  extract  the  square  root  for  the  diameter  of  the 
pipe  and  take  the  nearest  commercial  size. 

Example*  —  Given  a  20"  X  48"  Corliss  engine  making  72  revo- 
lutions per  minute.  What  should  be  the  diameter  of  its  steam 
pipe?  Ans.  6  inches. 


HANDBOOK   ON   ENGINEERING.  395 


Operation.— 20  X  20  X  .7854  =314.16  sqr.  ins. 
And,  48"  X  2  X  72  =576  ft.  the  piston  speed. 

And>  314.16  X  576  =30>15> 
6,000 

Then,    .  1^.  =  6.1".    Take  6" pipe. 


To  find  the  water  consumption  of  a  steam  engine:  — 
The  most  reliable  method  for  determining  this,  is  to  make  an 
evaporation  test,  that  is,  to  measure  the  water  fed  to  the  boiler  in 
a  given  time  and  delivered  to  the  engine  in  the  form  of  steam. 
But  as  this  method  entails  considerable  trouble  and  expense,  it  is 
frequently  figured  from  indicator  diagrams.  This  plan,  however, 
does  not  insure  correct  results,  because  the  amount  of  water  ac- 
counted for  by  the  indicator  is  considerably  less  than  it  should  be 
owing  to  cylinder  condensation  and  leakage,  so  that  it  might  be 
possible  that  only  80  per  cent  of  the  water  passing  through  the 
cylinder  would  be  accounted  for  by  the  indicator.  But  the  cal- 
culation, used  in  connection  with  an  evaporation  test,  will  reveal 
the  extent  of  the  losses  caused  by  cylinder  condensation  and 
leakage,  by  deducting  the  amount  of  water  found  by  computation 
from  the  amount  of  water  fed  to  the  boiler  while  making  an 
evaporation  test. 

Rule*  4-  Divide  the  constant  number  859,375  by  the  M.  E.  P. 
of  any  indicator  card,  and  divide  this  quotient  by  the  volume  of 
its  total  terminal  pressure,  the  result  will  be  the  theoretical  con- 
sumption in  pounds  of  water  per  horse  power  per  hour. 
The  constant  number  859,375  is  found  as  follows:  — 
Compute  the  size  of  an  engine  that  will  give  just  one  horse- 
power at  one  pound  M.  E.  P.  per  square  inch,  thus: 
Area  of  piston  equals  412.5  sqr.  inches. 
Stroke  equals  4  feet,  and  revolutions  per  minute  equal  10. 


396 


HANDBOOK    ON    ENGINEERING. 


Then,  the  piston  speed  is  (4  x  2  X  10)  80  feet  per  minute. 
A   *    412.5X1X80 

33,000 

To  find  how  much  water  it  would  take  to  run  this  engine  one 
hour,  allowing  62 1  Ibs.  to  the  cubic  foot  of  water,  proceed  as 
follows :  — 

Twice  the  stroke  equals  96  inches. 
412.5  X  96 


Then    _nzir_l_l_LI-    equals  22.91666  cubic  feet  for  one  revo- 
1728 

lution. 

And,  22.91666  X  10  equals  229.1666  cubic  feet  for  10  revolu- 
tions, or  for  one  minute. 

Then,  229,1666  X  60  X  62 £  equals  859,375  Ibs.  of  water  used 
per  hour. 


SCALE  40 

M.  E.  P. 
37.  6  LBS. 


Fig.  250.    Finding  steam  consumption  from  the  diagram. 

Fig.  250  is  not  an  actual  indicator  card,  but  answers  to 
illustrate  the  rule. 

A  A  is  the  atmospheric  line,  and  from  A  to  A  is  the  whole 
stroke. 

VV  is  the  vacuum  line. 

Points  (a)  and  (b  )  are  equally  distant  from  the  vacuum  line. 
The  point  (a)  is  taken  at  or  very  near  the  point  of  release. 


HANDBOOK   ON   ENGINEERING. 


397 


Example. —  From  the  indicator  card  Fig.  250  compute  the  water 
consumption,  the  M.  E.  P.  being  37.6  Ibs.  per  square  inch,  the 
scale  of  spring  used  in  the  indicator  being  40,  the  distance  from 
point  (a)  to  point  (6)  being  3.03  inches,  the  stroke  AA  being 
3.45  inches,  and  the  pressure  at  point  (a)  being  25  Ibs.  per  sqr. 
inch  absolute.  Ans.  20.14  Ibs. 

Operation*—  859,375  ~  37.6  =  22,855.7. 

Now,  the  absolute  pressure  at  point  (a)  is  25  Ibs.,  and  steam 
tables  give  996  as  the  volume  of  steam  at  this  pressure,  that  is, 
steam  at  this  pressure  has  996  times  the  bulk  of  the  water  from 
which  it  was  generated. 

Then,  22,855.7  -f-  996  =  22.94  Ibs.  of  water.  But  as  the 
period  of  consumption  is  represented  by  (&)  (a),  AA  being  the 
whole  stroke,  the  following  correction  is  required:  The  distance 
from  point  (a)  to  point  (6)  is  3.03  ins.  Then,  22.94  X  3.03  = 
69.5080.  And  the  whole  stroke  or  length  of  line  AA  is  3.45 
ins. 

Then,  69.5080-^-3.45  =20.14  Ibs.  of  water  per  indicated 
horse  power  per  hour. 

Boiler  Feed  or  Pressure  Pumps. 

SIZES  AND  CAPACITIES. 


tl 


1 


I. 

CJ 

IJ 

O 


Capacity  per  minute  at 
ordinary  speed. 


!» 

¥ 

5 

r 
I* 

10 
12 
14 

16 

18 

20 


14 

i* 

I 
ft 

J* 

5 

6 

7 

8 
10 
12 
14 


.031 

.05 

.07 

.11 

.25 

.35 


1.02 
1.47 
2.00 
2.61 
5.44 
11.75 
16.00 


150  Strokes.  34  gals. 
150       "         4iJ£    •' 
74    " 
104    " 

]?*  " 

42 

49 

69 

85 
102 
147 
200 
261 
408 
588 
800 


150 
150. 
150 
125 
125 
125 
100 
100 
100 
100 
100 
100 
75 
50 
50 


10 


17x.5 
18x  5 
26x  6 
28x7 
31  x  8 
44x13 
45x14 
45x14 
55x16 
55x16 
67x19 
67x19 
67x20 
67x20 
80x22 
110x27 
111x29 


25 

40 
60 
.90 
130 
160 
200 
250 
300 
400 
600 


398  HANDBOOK    ON    ENGINEERING. 


CHAPTER     XVI. 

THE  STEAM  BOILER. 
THE  FORCE  OF  STEAM  AND  WHERE  IT  GOMES  FROfl. 

If  water  be  heated  it  will  expand  somewhat,  and  will  finally 
burst  forth  into  vapor.  The  vapor  will  expand  enormously,  and 
naturally  occupy  more  space  than  the  water  from  which  it  is 
formed.  A  cubic  inch  of  water  will  make  a  cubic  foot  of  steam  ; 
that  is,  the  water  has  been  expanded  by  heat  to  seventeen  hundred 
times  its  original  bulk.  The  steam  is  very  elastic  ;  the  water  was 
not.  When  we  say  that  a  cubic  inch  of  water  will  form  a  cubic 
foot  of  steam,  we  mean  that  it  will  do  so  when  the  steam  is  allowed 
to  rise  naturally  from  the  water  without  any  confinement.  If  the 
steam  is  confined,  as  it  would  be  in  a  boiler,  it  could  not  expand, 
and  consequently  would  not.  If  the  steam  is  allowed  to  rise  into  the 
atmosphere  from  an  open  vessel,  the  pressure  of  the  steam  would  be 
precisely  the  same  as  the  pressure  of  the  atmosphere,  that  pressure 
being  about  fifteen  pounds  to  the  square  inch.  An  ordinary  steam 
gauge  only  takes  notice  of  the  pressure  above  the  atmospheric 
pressure.  When  the  hand  of  the  steam  gauge  stands  at  zero,  it 
indicates  that  there  is  no  pressure  above  the  ordinary  pressure  of 
the  atmosphere.  An  ordinary  steam  gauge  not  connected  with 
anything  has  the  atmosphere  acting  upon  it  in  both  directions,  the 
same  as  the  atmosphere  acts  upon  everything  when  it  can  reach 
both  sides.  If  the  air  be  pumped  out  of  the  steam  gauge,  the 
atmosphere  will  then  act  upon  one  side,  and  the  hand  will  move 
backward  until  it  stands  at  fifteen  points  less  than  zero.  In 
this  condition  the  steam  gauge  indicates  the  absolute  zero  of 
pressure.  If  now  the  air  be  allowed  to  re-enter  where  it  was 

pumped  out,  it  will  begin  to  exert  its  pressure  upon  the  jsteara 

:    .  !  - 


HANDBOOK    ON    ENGINEERING.  399 

gauge,  and  the  hand  will  move  forward ;  when  the  full  air 
pressure  is  on,  the  gauge  hand  will  stand  at  its  usual  zero. 
To  gx>  into  this  matter  in  order  that  it  may  be  understood 
that  the  real  pressure  of  steam  is  always  fifteen  pounds  greater 
than  ordinary  steam  gauges  indicate.  In  all  of  the  finer  cal- 
culations relating  to  the  action  of  steam,  its  total  pressure  must 
be  known,  and  this  total  pressure  is  to  be  counted  from  the 
absolute  zero.  The  real  pressure  of  steam  is  always  the  steam 
gauge  pressure,  plus  fifteen  pounds.  When  a  steam  gauge  shows 
fifty  pounds,  the  steam  really  has  a  pressure  of  sixty-five  pounds. 
The  fifteen  pounds  of  this  pressure  is  nullified  by  the  atmospheric 
pressure,  and  the  steam  gauge  shows  us  our  useful  pressure.  As 
before  stated,  a  cubic  inch  of  water  will  make  a  cubic  foot  of 
steam  at  atmospheric  pressure ;  that  is,  fifteen  pounds  to  the 
square  inch,  abolute  pressure,  or  zero  by  the  steam  gauge.  If 
this  cubic  inch  of  water  was  made  into  steam  in  a  boiler  holding 
just  a  cubic  foot,  the  steam  gauge  would  show  zero.  If  the  boiler 
was  only  large  enough  to  hold  half  a  cubic  foot,  the  steam  would 
all  be  in  the  boiler,  and  being  con  lined  in  half  its  natural  space, 
it  would  have  double  pressure.  It  would  have  an  absolute  pres- 
sure of  thirty  pounds  to  the  square  inch,  and  the  steam  gauge 
would  indicate  fifteen  pounds.  If  this  steam  was  then  allowed  to 
pass  into  a  chamber  holding  a  cubic  foot,  the  steam  would  expand 
until  it  filled  the  chamber,  and  its  pressure  would  go  down  again 
to  fifteen  pounds  absolute.  In  short,  the  pressure  is  in  reverse 
proportion  to  the  amount  of  space  it  occupies.  The  pressure  of 
steam  may  be  doubled  by  compressing  the  steam  into 
one-half  its  former  volume,  and  so  on.  After  water  is 
turned  into  steam,  the  steam  may  be  made  hotter,  but 
it  is  not  very  much  expanded.  The  pressure  of  steam 
is  increased  by  forcing  more  steam  into  the  space  occupied. 
If  a  boiler  contains  steam  at  50  Ibs.  pressure,  we  may  increase 
the  pressure  by  adding  more  steam,  and  thus  compressing  all  the 


400  HANDBOOK    ON    ENGINEERING. 

steam  that  the  boiler  contains.  In  the  ordinary  operation  of  a 
steam  boiler,  the  fire  turns  the  water  into  steam  and  the  more 
steam  there  is  made  and  confined,  the  greater  the  pressure  will 
be.  If  the  steam  is  constantly  flowing  out  of  the  boiler  into  an 
engine,  the  pressure  in  the  boiler  must  be  kept  up  by  continually 
making  new  steam  to  take  the  place  of  that  drawn  off.  If  we 
make  steam  as  fast  as  it  is  drawn  off,  and  no  faster,  the  pressure 
will  remain  the  same.  If  we  make  steam  faster  than  the  engine 
draws  it  off,  the  pressure  will  rise,  and  if  it  is  drawn  off  faster 
than  we  make  it,  the  pressure  will  go  down. 

The  pressure  of  the  steam  is  due  to  its  desire  to  expand  into  a 
larger  body,  and  it  acts  outwardly  in  every  direction  against 
everything  upon  which  it  presses.  If  we  crowd  600  cu.  ft.  of 
steam  in  a  boiler,  which  will  only  hold  100  cu.  ft.,  the  steam  will 
be  held  compressed  into  one-sixth  its  natural  bulk,  and  will  thus 
have  a  pressure  of  90  Ibs.,  and  the  steam  gauge  will  show  75  Ibs. 
If  a  hole  1  in.  square  be  cut  in  the  boiler,  and  a  weight  of  75  Ibs. 
be  laid  over  the  hole,  the  steam  will  just  lift  the  weight.  If  the 
atmospheric  pressure  could  be  removed  from  one  sq.  in.  of  the 
top  of  the  weight,  the  steam  would  then  be  capable  of  lifting  a 
90  Ib.  weight.  The  force  which  this  steam  will  exert  to  lift  a 
weight,  or  any  similar  thing  against  which  it  acts,  will  equal  the 
pressure  per  square  inch  multiplied  by  the  number  of  square 
inches  which  the  steam  acts  upon.  It  will  thus  be  readily  under- 
stood that  if  we  lead  a  pipe  from  the  boiler  and  fit  a  piston  in  the 
pipe,  the  steam  will  tend  to  force  this  piston  out  of  the  pipe. 

THE   ENERGY   STORED   IN  STEAM   BOILERS. 

A  steam  boiler  is  not  only  an  apparatus  by  means  of  which  the 
potential  energy  of  chemical  affinity  is  rendered  actual  and  avail- 
able, but  it  is  also  a  storage  reservoir,  or  a  magazine,  in  which  a 
quantity  of  such  energy  is  temporarily  held ;  and  this  quantity, 


HANDBOOK    ON    ENGINEERING.  401 

always  enormous,  is  directly  proportional  to  the  weight  of  water 
and  of  steam  which  the  boiler  at  the  time  contains.  The  energy 
of  gunpowder  is  somewhat  variable,  but  a  cubic  foot  of  heated 
water  under  a  pressure  of  60  or  70  Ibs.  per  square  inch,  has  about 
the  same  energy  as  one  pound  of  gunpowder ;  at  a  low  red  heat, 
it  has  about  forty  times  this  amount  of  energy. 

The  letters  B.  T.  U.  are  the  initial  letters  of  the  words  British 
Thermal  Unit,  and  are  used  as  abbreviations  of  those  words. 
The  British  Thermal  Unit  is  the  unit  of  heat  used  in  this  country 
and  England,  and  may  be  said  to  be  the  amount  of  heat  required 
to  raise  the  temperature  of  one  pound  of  pure  water  from  39  to  40 
degrees  Fahr.  It  is  often  necessary  to  distinguish  between 
B.  T.  U.  used  in  this  country  and  the  French  thermal  unit  used  in 
France  and  most  of  the  countries  of  Europe.  The  French  ther- 
mal unit  is  called  the  calorie,  and  is  the  heat  required  to  raise  the 
temperature  of  one  kilogram  of  water  one  degree  centigrade. 

Safety  at  high  pressure  depends  entirely  upon  the  design, 
material,  and  workmanship,  and  it  is  a  question  that  may  be  re- 
garded as  settled  long  since,  that  a  steam  boiler  properly  con- 
structed and  designed  for  a  working  pressure  of  150  pounds  is  as 
safe  as  a  properly  constructed  boiler  designed  for  eighty  pounds, 
with  the  chances  in  favor  of  the  high  pressure,  for  the  reason  that 
less  care  is  taken  in  selecting  boilers  for  the  ordinary  pressure,  as 
anything  in  the  shape  of  a  boiler  is  regarded,  fry  careless  people, 
as  good  enough  for  the  lower  pressures,  with  which  they  have 
become  so  familiar  as  to  become  almost  too  careless. 

SPECIAL  HIGH   PRESSURE  BOILERS. 

The  extending  use  of  compound  steam  engines,  which  make 
necessary  the  employment  of  high  steam  pressures,  calls  for  steam 
boilers  specially  designed  to  successfully  operate  under  working 
pressures  ranging  from  100  to  160  pounds.  These  boilers  must 
be  safe  and  economical  and  of  such  construction  as  to  afford 

26 


402  HANDBOOK    ON    ENGINEERING. 

access  for  examination  and  repair,  moderate  in  first  cost  and 
maintenance  and  of  simplest  possible  form.  Fortunately,  the 
controlling  conditions  are  not  difficult  to  meet,  and  there  are  sev- 
eral well-tried  and  approved  types  Of  steam  boilers  from  which  to 
make  a  selection,  choice  being  governed  by  the  space  at  dis- 
posal, arrangement  of  plant,  kind  of  fuel  and  other  circum- 
stances. 

TYPES  OF  BOILERS. 

Four  types  that  are  very  succesfully  used,  and  they  represent 
good  practice  for  high  pressure  w^>rk,  being  respectively  the  Hori- 
zontal Tubular,  and  Vertical  Fixe  Box  Tubular  Boilers.  The  Fire 
Box  Locomotive  Tubular  Boiler  may  safely  be  added  to  this  list 
and  gives  most  excellent  results. 

THE  WATER  TUBE  BOILER. 

Steam  boilers  must  be  designed  with  reference  to  the  pres- 
sure of  steam  to  be  carried,  and  when  so  designed  and  constructed 
are  quite  as  safe  at  one  pressure  as  another,  preference  being 
given  to  the  type  that  is  simplest  in  form  and  the  least  liable  to 
destruction,  not  so  much  jj  reason  of  the  pressure  carried  as  by 
failure  to  provide  for  the  strains  of  expansion  and  contraction 
within  itself. 

HORSE  POWER  OF  BOILERS. 

In  determining  the  proper  size  or  evaporating  capacity  of  a 
boiler  to  supply  steam  for  a  given  purpose,  it  is  necessary  to  con- 
sider the  number  of  pounds  of  dry  steam  actually  required  per 
hour  at  the  stated  pressure.  The  standard  horse  power  rating 
for  any  steam  boiler  is  34^  pounds  of  water  evaporated  (made  into 
steam)  from  feed  water  at  212°,  per  hour.  The  total  pounds 
steam  required  for  any  purpose  per  hour  on  this  basis  divided  by 
34J  will  give  the  standard  boiler  horse  power  required.  Manu- 


HANDBOOK    ON    ENGINEERING.  403 

facturers  of  steam  boilers  sometimes  rate  the  horse  power  of  their 
boilers  by  so  many  square  feet  of  heating  surface  per  horse  power  ; 
8  to  15  sq.  ft.  of  heating  surface,  they  figure,  equals  one  horse 
power.  This  rating  does  not  represent  the  actual  capacity  of  the 
steam  boiler,  the  only  safe  guide  being  the  evaporative  perform- 
ance in  pounds  of  steam  from  water  at  212°  to  steam  at  212°. 
Some  boilers  will  evaporate  this  with  8  sq.  ft.,  some  requiring 
from  15  to  18  sq.  ft.,  hence,  the  absurdity  of  rating  horse  power 
of  boilers  of  unlike  construction  by  the  square  feet  of  heating 
surface.  But  as  the  practice  is  an  old  one  in  the  case  of  the 
well-known  tubular  boiler,  so  deservedly  popular  and  used  more 
than  any  other  kind,  good  practice  is  to  allow  approximately  as 
follows:  — 

Allow  for  each  Horse  Power- 
Steam  for  Heating,  etc.     ....  15  sq.  ft.  heating  surface. 
For  Plain  Throttle  Engine,     ...  15          "          "          " 
For  Simple  Corliss  Engine       ...  12          "          "          " 
For  Compound  Corliss  Condensing  .  10         "          "          " 

Hence,  a  boiler  for  heating  purposes  or  furnishing  steam  for  — 

Plain  Slide  engine  with  1,500  sq.  ft.  surface,  equals  .  100  H.  P. 
For  Simple  Corliss  Engine,  same  boiler  "  .  125  H.  f. 

For  Compound  Condensing  Engine  "      .  .      150  H.  P. 

The  best  method  is  to  compare  boilers  by  their  evaporative 
efficiency  and  not  by  heating  surface. 

The  following  is  an  approximate  consumption  of  steam  per 
indicated  horse  power  per  hour  for  engine :  — 

Plain  Slide  Engine    . 60  to  70  pounds. 

High  Speed  Automatic  Engine     .     .     .     .      .  30  to  50      .  " 

Simple  Corliss  Engine' 25  to  35       " 

Compound  Corliss  Engine       .     .     .     .     .     .  15  to  20       " 

Triple  Expansion  Engine  .     .     .     ...     .  13  to  17       <; 


404  HANDBOOK    ON    ENGINEERING. 

depending  upon  the  horse  power,   steam   pressure,   condition  of 
engine,  load,  etc. 

Each  pound  of  first-class  steam  coal  consumed  under  a  well- 
proportioned  steam  boiler,  well  managed,  should  evaporate  10 
pounds  of  water  at  212°  into  dry  steam  at  212°.  The  average 
boiler  throughout  the  country,  with  ordinary  fuel  and  manage- 
ment, ranges  from  5  to  8  pounds  steam  per  pound  of  coal,  and  it 
would  scarcely  be  safe  to  make  fuel  guarantees  per  horse  power 
of  engine  without  a  counter  guarantee  on  the  part  of  the  pur- 
chaser, when  his  old  boiler  is  used,  that  the  fuel  economy  is  based 
on  an  evaporative  efficiency  of  a  given  weight  of  water  evaporated 
per  pound  of  coal  per  hour  in  his  boiler.  The  usual  practice  is 
to  ignore  the  boiler  altogether  and  guarantee  pounds  of  steam 
per  indicated  horse  power  per  hour  used  by  the  engine.  This 
affords  an  exact  method  and  is  not  hampered  by  unknown  con- 
ditions, and  places  all  tests  on  an  equal  or  comparative  basis. 

THE   RATING  OF  BOILERS. 

It  is  considered  usually  advisable  to  assume  a  set  of  practically 
attainable  conditions  in  average  good  practice,  and  to  take  the 
power  so  obtainable  as  the  measure  of  the  power  of  the  boiler  in 
commercial  and  engineering  transactions.  The  unit  generally 
assumed  has  been  usually  the  weight  of  steam  demanded  per  horse 
power  per  hour  by  a  fairly  good  steam  engine.  In  the  time  of 
Watt,  one  cubic  foot  of  water  per  hour  was  thought  fair ;  at  the 
middle  of  the  last  century,  ten  pounds  of  coal  was  a  usual 
figure,  and  five  pounds,  commonly  equivalent  to  about  40  Ibs.  of 
feed  water  evaporated,  was  allowed  the  best  engines.  After  the 
introduction  of  the  modern  forms  of  engine,  this  last  figure  was 
reduced  25  per  cent,  and  the  most  recent  improvements  have  still 
further  lessened  the  consumption  of  fuel  and  of  steam.  By  general 
consent  the  unit  has  now  become  thirty  pounds  of  dry  steam  per 


HANDBOOK    ON    ENGINEERING.  405 

horse  power  per  hour,  which  represents  the  performance  of  non- 
condensing  engines.  Large  engines,  with  condensers  and  com- 
pound cylinders,  will  do  still  better.  A  committee  of  the 
American  Society  of  Mechanical  Engineers  recommended  thirty 
pounds  as  the  unit  of  boiler  power,  and  this  is  now  generally 
accepted.  They  advised  that  the  commercial  horse-power  be 
taken  as  an  evaporation  of  30  Ibs.  of  water  per  hour  from  a  feed 
water  temperature  of  100°  Fahr.  into  steam  at  70  Ibs.  gauge  pres- 
sure, which  may  be  considered  equal  to  34 £  Ibs.  of  water  evapo- 
ration, that  is,  34  J  Ibs.  of  water  evaporated  from  a  feed  water 
temperature  of  212°  Fahr.  into  steam  at  the  same  temperature. 
This  standard  is  equal  to  33,305  British  thermal  units  per  hour. 
A  boiler  rated  at  any  stated  power  should  be  capable  of 
developing  that  power  with  easy  firing,  moderate  draught  and 
ordinary  fuel,  while  exhibiting  good  economy,  and  at  least 
one-third  more  than  its  rated  power  to  meet  emergencies. 

WORKING  CAPACITY  OF  BOILERS. 

The  capacity  or  horse-power  of  a  boiler,  as  rated  for  purposes 
of  the  trade,  is  commonly  based  upon  the  extent  of  heating 
surface  which  it  contains.  The  ordinary  rating  was  for  a  long 
time  15  sq.  ft.  of  surface  per  horse-power.  At  the  present  time 
most  of  the  stationary  boilers  are  sold  on  the  basis  of  from  10  to 
12  sq.  ft.  per  horse-power,  the  power  referred  to  being  the  unit 
of  30  Ibs.  evaporation  per  .hour.  This  method  of  rating  is  arbi- 
trary, inasmuch  as  it  is  independent  of  any  condition  pertaining 
to  the  practical  work  of  the  boiler.  The  fact  that  10  or  12  sq. 
ft.  of  surface  is  sold  for  one  horse-power  is  no  guarantee  that  this 
extent  of  surface  will  have  a  capacity  of  one  horse-power  when 
the  boiler  is  installed  and  set  to  work.  The  boiler  in  service 
and  the  boiler  in  the  shop  are  two  entirely  different  things,  and 
where  one  passes  to  the  other,  the  trade  rating  disappears.  New 


406  HANDBOOK    ON   ENGINEERING. 

conditions,  such  as  draft,  grate  surface,  kind  of  fuel  and  man- 
agement, then  take  effect,  and  these  have  a  controlling  influence 
upon  the  working  capacity.  The  working  power  may  be  found 
to  be  much  less  than  the  arbitrary  rate,  or  it  may  be  a  much 
larger  quantity ;  all  depending  upon  the  surrounding  conditions, 
attention  is  had  to  this  subject,  because  it  is  important  in  some 
cases  to  have  a  clearer  understanding  as  to  what  is  the  working 
capacity  of  a  boiler.  Suppose  a  boiler  manufacturer  enters  into 
an  agreement  to  install  a  boiler,  which  will  have  a  capacity  of  100 
horse-power.  Suppose  that  on  account  of  poor  draft,  low  grade 
of  fuel,  or  unfavorable  surroundings,  all  of  which  are  known 
beforehand,  the  boiler  develops  the  power  named  only  with  the 
most  careful  handling.  Is  the  working  capacity,  under  the  cir- 
i  cumstances,  100  horse-power?  Assuredly  not,  for  the  purchaser 
could  not  depend  upon  it  in  ordinary  running  for  that  amount  of 
power.  Yet  the  builder  may  claim  that  he  has  fulfilled  his 
contract. 

The  former  boiler  test  committee  of  the  American  Society  of 
Mechanical  Engineers  established  a  working  rate  for  boiler  capac- 
ity which  meets  such  cases  in  a  definite  and  satisfactory  manner. 
They  realized  that  for  the  purpose  of  good  work,  a  boiler  should 
be  capable  of  developing  its  capacity  with  a  moderate  draft  and 
easy  firing;  and  that  it  should  be  capable  of  doing  one-third  more 
in  cases  of  emergency.  In  other  words,  a  boiler  which  is  sold 
for  100  horse-power  should  develop  133^  horse-power  under  con- 
ditions giving  a  maximum  capacity.  .In  the  instance  cited  above, 
the  boiler  should  have  been  capable  of  giving  100  horse-power 
with  such  ease  that  there  would  be  a  reserve  of  33|  horse-power 
available  when  urged  to  this  extra  power.  According  to  this 
rule,  the  capacity  of  a  boiler  in  a  working  plant  would  be  found 
by  determining  how  much  water  it  can  evaporate  under  conditions 
which  will  give  its  maximum  capacity ;  that  is,  with  w^de  open 
damper,  with  the  maximum  draft  available  arid  with  the  best  con- 


HANDBOOK    ON    ENGINEERING.  407 

ditions  as  to  the  handling  of  the  fire,  and  in  this  way  ascertain 
the  maximum  power  available  under  these  circumstances.  Hav- 
ing found  this  maximum  quantity,  the  working  capacity  or  the 
rated  power  would  be  determined  by  deducting  from  the  maxi- 
mum 25  per  cent.  This  rule,  it  will  be  seen,  does  not  take  into 
account  the  extent  of  the  heating  surface  or  the  trade  rating,  but 
it  deals  solely  with  the  capabilities  of  the  boiler  under  the  con- 
ditions which  pertain  to  its  work. 

CODE  OF  RULES  FOR  BOILER  TESTS. 

Starting  and  stopping  a  test*  —  A  test  should  last  at  least 
ten  hours  of  continuous  running,  and  twenty-four  hours  whenever 
practicable.  The  conditions  of  the  boiler  and  furnace  in  all 
respects  should  be,  as  nearly  as  possible,  the  same  at  the  end 
as  at  the  beginning  of  the  test.  The  steam  pressure  should  be 
the  same ;  the  water  level  the  same ;  the  fire  upon  the  grates 
should  be  the  same  in  quantity  and  condition  ;  and  the  walls,  flues, 
etc.,  should  be  of  the  same  temperature.  To  secure  as  near  an 
approximation  to  exact  conformity  as  possible  in  conditions  of 
the  fire  and  in  the  temperature  of  the  walls  and  flues,  the  follow- 
ing method  of  starting  and  stopping  a  test  should  be  adopted :  — 

Standard  method* — Steam  being  raised  to  the  working  pres- 
sure, remove  rapidly  all  the  fire  from  the  grate,  close  the  damper, 
clean  the  ash-pit,  and,  as  quickly  as  possible,  start  a  new  fire  with 
weighed  wood  and  coal,  noting  the  time  of  starting  the  test  and 
the  height  of  the  water  level  while  the  water  is  in  a  quiescent 
state,  just  before  lighting  the  fire.  At  the  end  of  the  test,  re- 
move the  whole  fire,  clean  the  grates  and  ash-pit,  and  note  the 
water-level  when  the  water  is  in  a  quiescent  state  ;  record  the  time 
of  hauling  the  fire  as  the  end  of  the  test.  The  water-level  should 
be  as  nearly  as  possible  the  same  as  at  the  beginning  of  the  test. 
If  it  is  not  the  same,  a  correction  should  be  made  by  computa- 


408  HANDBOOK    ON    ENGINEERING. 

tion,  and  not  by  operating  pump  after  test  is  completed.  It  will 
generally  be  necessary  to  regulate  the  discharge  of  steam  from  the 
boiler  tested  by  means  of  the  stop-valve  for  a  time  while  fires  are 
being  hauled  at  the  beginning  and  at  the  end  of  the  test,  in  order 
to  keep  the  steam  pressure  in  the  boiler  at  those  times  up  to  the 
average  during  the  test. 

Alternate  method*  —  Instead  of  the  standard  method  above 
described,  the  following  may  be  employed  where  local  conditions 
render  it  necessary :  At  the  regular  time  for  slicing  and  cleaning 
fires  have  them  burned  rather  low,  as  is  usual  before  cleaning, 
and  then  thoroughly  cleaned ;  note  the  amount  of  coal  left  on  the 
grate  as  nearly  as  it  can  be  estimated  ;  note  the  pressure  of  steam 
and  the  height  of  the  water-level  —  which  should  be  at  the  medium 
height  to  be  carried  throughout  the  test  —  at  the  same  time  ;  and 
note  this  time  as  the  time  for  starting  the  test.  Fresh  coal  which 
has  been  weighed,  should  now  be  fired.  The  ash-pits  should  be 
thoroughly  cleaned  at  once  before  starting.  Before  the  end  of  the 
test  the  fires  should  be  burned  low,  just  as  before  the  start,  and 
the  fires  cleaned  in  such  a  manner  as  to  leave  the  same  amount 
of  fire,  and  in  the  same  condition,  on  the  grates  as  on  the  start. 
The  water-level  and  steam  pressure  should  be  brought  to  the  same 
point  as  at  the  start,  and  the  time  of  the  ending  of  the  test  should 
be  noted  just  before  fresh  coal  is  fired. 

DURING  THE  TEST. 

Keep  the  conditions  uniform,  —  The  boiler  should  be  run  con- 
tinuously without  stopping  for  meal  times,  or  for  rise  or  fall  of 
pressure  of  steam  due  to  change  of  demand  for  steam.  The 
draught  being  adjusted  to  the  rate  of  evaporation  or  combustion 
desired  before  the  test  is  begun,  it  should  be  retained  constant 
during  the  test  by  means  of  the  damper.  If  the  boiler  is  not  con- 
nected to  the  same  steam  pipe  with  other  boilers,  an  extra  outlet 


HANDBOOK    ON    ENGINEERING.  409 

for  steam  with  valve  in  same  should  be  provided,  so  that  in  case 
the  pressure  should  rise  to  that  at  which  the  safety  valve  is  set,  it 
may  be  reduced  to  the  desired  point  by  opening  the  extra  outlet, 
without  checking  the  fire.  If  the  boiler  is  connected  to  a  main 
steam  pipe  with  other  boilers,  the  safety  valve  on  the  boiler  being 
tested  should  be  set  a  few  pounds  higher  than  those  of  the  other 
boilers,  so  that  in  case  of  a  rise  in  the  pressure  the  other  boilers 
may  blow  off,  and  the  pressure  be  reduced  by  closing  their  dam- 
pers, allowing  the  damper  of  the  boiler  being  tested  to  remain 
open,  and  firing  as  usual.  All  the  conditions  should  be  kept  ai 
nearly  uniform  as  possible,  such  as  force  of  draught,  pressure  of 
steam  and  height  of  water.  The  time  of  cleaning  the  fires  will 
depend  upon  the  character  of  the  fuel,  the  rapidity  of  combustion 
and  the  kind  of  grates.  When  very  good  coal  is  used  and  the 
combustion  not  too  rapid,  a  ten-hour  test  may  be  run  without  any 
cleaning  of  the  grates,  other  than  just  before  the  beginning  and 
just  before  the  end  of  the  test.  But  in  case  the  grates  have  to  be 
cleaned  during  the  test,  the  intervals  between  one  cleaning  and 
another  should  be  uniform. 

Keeping  the  records*  —  The  coal  should  be  weighed  and 
delivered  to  the  firemen  in  equal  portions,  each  sufficient  for  about 
one  hour's  run,  and  a  fresh  portion  should  not  be  delivered  until 
the  previous  one  has  all  been  fired.  The  time  required  to  con- 
sume each  portion  should  be  noted ,  the  time  being  recorded  at  the 
instant  of  firing  the  first  of  each  new  portion.  It  is  desirable  that 
at  the  same  time  the  amount  of  water  fed  into  the  boiler  should 
be  accurately  noted  and  recorded,  including  the  height  of  the 
water  in  the  boiler,  and  the  average  pressure  of  steam  and  tem- 
perature of  feed  during  the  time.  By  thus  recording  the 
amount  of  water  evaporated  by  successive  portions  of  coal,  the 
record  of  the  test  may  be  divided  into  several  divisions,  if  desired 
at  the  end  of  the  test,  to  discover  the  degree  of  uniformity  of  com- 
bustion, evaporation  and  economy  at  different  stages  of  the  test. 


410  HANDBOOK    ON    ENGINEERING. 

. 

PRIMING  TESTS. 

In  alt  tests  in  which  accuracy  of  results  is  important,  calori- 
meter tests  should  be  made  of  the  percentage  of  moisture  in  the 
steam,  or  of  the  degree  of  superheating.  At  least  ten  such 
tests  should  be  made  during  the  trial  of  the  boiler,  or  so  many  as 
to  reduce  the  probable  average  error  to  less  than  one  per  cent, 
and  the  final  records  of  the  boiler  tests  corrected  according  to  the 
average  results  of  the  calorimeter  tests.  On  account  of  the 
difficulty  of  securing  accuracy  in  these  tests,  the  greatest  care 
should  be  taken  in  the  measurements  of  weights  and  temperatures. 
The  thermometers  should  be  accurate  to  within  a  tenth  of  one 
degree,  and  the  scales  on  which  the  water  is  weighed  to  within 
one-hundredth  of  a  pound. 

ANALYSES  OF  GASES. 

• 

Measurement  of  air  supply,  etc* —  In  tests  for  purposes  of 
scientific  research,  in  which  the  determination  of  all  the  variables 
entering  into  the  test  is  desired,  certain  observations  should  be 
made  which  are  in  general  not  necessary  in  tests  for  commercial 
purposes.  These  are  the  measurements  of  the  air  supply,  the 
determination  of  its  contained  moisture,  the  measurement  and 
analysis  of  the  flue  gases,  the  determination  of  the  amount  of  heat 
lost  by  radiation,  of  the  amount  of  infiltration  of  air  through  the 
setting,  the  direct  determination  by  calorimeter  experiments  of 
the  absolute  heating  value  of  the  fuel,  and  (by  condensation  of 
all  the  steam  made  by  the  boiler)  of  the  total  heat  imparted  to 
the  water. 

The  analysis  of  the  flue  gases  is  an  especially  valuable 
method  of  determining  the  relative  value  of  different  methods  of 
firing,  or  of  different  kinds  of  furnaces.  In  making  these 
analyses,  great  care  should  be  taken  to  procure  average  samples 


HANDBOOK    ON    ENGINEERING. 


411- 


since  the  composition  is  apt  to  vary  at  different  points  of  the  flue, 
and  the  analyses  should  be  intrusted  only  to  a  thoroughly  com- 
petent chemist,  who  is  provided  with  complete  and  accurate 
apparatus.  As  the  determination  of  the  other  variables  men- 
tioned above  are  not  likely  to  be  undertaken  except  by  engineers 
of  high  scientific  attainments,  and  as  apparatus  for  making  them 
is  likely  to  be  improved  in  the  course  of  scientific  research,  it  is 
not  deemed  advisable  to  include  in  this  code  any  specific  direc- 
tions for  making  them. 

RECORD  OF  THE  TEST. 

A  "  log "   of  the  test   should   be  kept  on  properly   prepared 
blanks,  containing  headings  as  follows  :  — 


PRESSURES. 

TEMPERATURES. 

FUEL. 

FEED  WATER. 

8c 

« 

. 

£ 

bJD 

oj 

id 

ed 

2 

<u 

p 

bJD 

cS 

P 

o 

TIME. 

Barome 

1 
1 

W) 

<M 

Externa 

Boiler  r 

. 

V 

P 

E 

Feed  w£ 

Steam. 

i 
S 

Pounds 

1 
H 

b 

'  0 

s 

REPORTING  THE  TRIAL. 

The  final  results  should  be  recorded  upon  a  properly  prepared 
blank,  and  should  include  as  many  of  the  following  items  as  are 
adapted  for  the  specific  -object  for  which  the  trial  is  made.  The 
items  marked  with  a  *  may  be  omitted  for  ordinary  trials,  but  are 
desirable  for  comparison  with  similar  data  from  other  sources. 


412  HANDBOOK    ON    ENGINEERING. 


Resources  of  the  trials  of  a 

Boiler  at 

To  determine 

1.  Date  of  trial     .     .     . 

2.  Duration  of  trial  . 


DIMENSIONS    AND    PROPORTIONS. 

3.  Grate-surface          wide         long         area 

4.  Water-heating  surface 

5.  Superheating  surface 

6.  Ratio  of  water-heating  surface  to  gr^te- 

surface 

AVERAGE    PRESSURES. 

7.  Steam  pressure  in  boiler,  by  gauge     .     .  Ibs. 

*8.  Absolute  steam  pressure Ibs. 

*9.  Atmospheric  pressure,  per  barometer      .  in. 

10.  Force  of  draught  in  inches  of  water  .  in. 

AVERAGE    TEMPERATURES. 

*11.  Of  external  air deg. 

*15.  Of  fire-room deg. 

*13.  Of  steam deg. 

14.  Of  escaping  gases deg. 

15.  Of  feed-water deg. 

FUEL. 

16.  Total  amount  of  coal  consumed     .     .     .  Ibs. 

17.  Moisture  in  coal per  cent. 

18.  Dry  coal  consumed Ibs. 

19.  Total  refuse,  dry  pounds  equals    .     .     .  per  cent. 

20.  Total  combustible  (dry  weight  of  coal, 

item  18,  less  refuse,  item  19)    .     .     .  Ibs. 

*21.  Dry  coal  consumed  per  hour     .  .     .  Ibs. 

*22.  Combustible  consumed  per  hour    .     .     .  Ibs. 


HANDBOOK    ON    ENGINEERING.  413 

RESULTS    OF    CALORIMETRIC    TESTS. 

23.  Quality  of  steam,  dry  steam  being  taken 

as  unity 

24.  Percentage  of  moisture  in  steam    .     .     0  per  cent. 

25.  Number  of  degrees  superheated     ...  deg. 

WATER. 

26.  Total  weight  of  water  pumped  into  boiler 

and  apparently  evaporated    ....  Ibs. 

27.  Water  actually  evaporated,  corrected  for 

quality  of  steam Ibs. 

28.  P^quivalent    water   evaporated    into    dry 

steam  from  and  at  212°  F Ibs. 

*29.  Equivalent  total  heat  derived  from  fuel 

in  B.  T.  U B.  T.  U. 

*30.  Equivalent    water    evaporated     in     dry 

steam  from  212°  F.  per  hour     .     .     .  Ibs. 

ECONOMIC    EVAPORATION. 

31.  Water  actually  evaporated  per  pound  of 

dry   coal,    from   actual   pressure    and 

temperature       .     • Ibs. 

32.  Equivalent  water  evaporated  per  pound 

of  dry  coal,  from  212°  F Ibs. 

33.  Equivalent  water  evaporated  per  pound 

of  combustible  from  and  at  212°  F.     .  Ibs. 

COMMERCIAL    EVAPORATION. 

34.  Equivalent  water  evaporated  per  pound 

of  dry  coal  with  one-sixth  refuse,  at  70 
Ibs.  gauge  pressure,  from  temperature  of 
100°  F.,  equals  item  tests  33  X.  0.7249 
pounds Ibs. 

f  Corrected  for  inequality  of  water  level  and  of  steam  pressure  at 
beginning  and  end  of  test. 


414 


HANDBOOK   ON    ENGINEERING. 


*       KATE    OF    COMBUSTION. 

35.  Dry  coal  actually  burned  per  sq.  foot  of 
grate-surface  per  hour      .     .     .     . 

Per  sq.  ft.  of  grate 
Consumption     of      dry         surface 
coal  per   hour.     Coal 
assumed     with     one- 
sixth  refuse. 


*36. 
*37. 
*38. 


Per  sq.  ft.  of  water 
heating  surface  . 

Per  sq.  foot  of  least 
area  for  draught. 


RATE    OF    EVAPORATION. 

39.  Water  evaporated  from  and  at  212°  F.  per 
square  foot  of  heading  surface  per  hour. 

Per  sq.  ft.  of  grate 
Water    evaporated    per 

hour  from  temperature 
of  100°  F.  into  steam 
of  70  Ibs.  gauge  pres- 
sure. 


*40. 
*41. 
*42. 


surface      . 

Per  sq.  ft.  of  heat- 
ing surface  . 

Per  sq.  ft.  of  least 
area  for  draught. 


COMMERCIAL   HORSE    POWER. 

43.  On  basis  of  30  Ibs.  of  water  per  hour 

evaporated  from  temperature  of  100°  F. 
into  steam  of  70  Ibs.  gauge  pressure 
(34£  Ibs.  from  and  at  212°)  ... 

44.  Horse-power,    builders'    rating  at 

sq.  ft.  per  horse-power     .     .     .     ,     . 

45.  Per  cent  developed  above  or  below  rating 


IDS. 

ibs. 

Ibs. 
Ibs. 


Ibs. 

Ibs. 


H.  P. 


per  cent. 


*  NOTE.  Items  20,  22,  33,  34,  36,  37,  38  are  of  little  practical  value. 
For  if  the  result  proves  to  be  less  satisfactory  than  expected  on  the 
actual  coal,  it  is  easy  for  an  expert  fireman  to  decrease  No.  20  by  simply 
taking  out  some  partly  consumed  coal  in  cleaning  fires,  and  thus  make  a 
fine  showing  on  that  simply  ideal  or  theoretical  unit,  the  u  pound  com- 
bustible." The  question  at  issue  is  always  what  can  be  done  with  an 
actual  coal,  not  the  "  assumed  coal  "  of  items  34,  36,  37  and  38. 


HANDBOOK    ON    ENGINEERING.  415 

DEFINITIONS    AS   APPLIED    TO  BOILERS   AND    BOILER 
flATERIALS. 

Cohesion  is  that  quality  of  the  particles  of  a,  body  which  causes 
them  to  adhere  to  each  other,  and  to  resist  being  torn  apart. 

Curvilinear  seams*  —  The  curvilinear  seams  of  a  boiler  are 
those  around  the  circumference. 

Elasticity  is  that  quality  which  enables  a  body  to  return  to  its 
original  form  after  having  been  distorted,  or  stretched  by  jsome 
external  force. 

Internal  radius*  —  The  internal  radius  is  one-half  of  the  diam- 
eter, less  the  thickness  of  the  iron.  To  find  the  internal  radius 
of  a  boiler,  take  one-half  of  the  external  diameter  and  substract 
the  thickness  of  the  iron. 

Limit  of  elasticity*  —  The  extent  to  which  any  material  may  be 
stretched  without  receiving  a  permanent  "  set." 

Longitudinal  seams*  —  The  seams  which  are  parallel  to  the 
length  of  a  boiler  are  called  the  longitudinal  seams. 

Strength  is  the  resistance  which  a  body  opposes  to  a  disinte- 
gration or  separation  of  its  parts. 

Tensile  strength  is  the  absolute  resistance  which  a  body  makes 
to  being  torn  apart  by  two  forces  acting  in  opposite  direc- 
tions. 

Crushing  strength  is  the  resistance  which  a  body  opposes  to 
being  battered  or  flattened  down  by  any  weight  placed  upon  it. 

Transverse  strength  is  the  resistance  to  bending  or  flexure,  as 
it  is  called. 

Torsional  strength  is  the  resistance  which  a  body  offers  to 
any  external  force  which  attempts  to  twist  it  round. 

Detrusive  strength  is  the  resistance  which  a  body  offers  to 
being  clipped  or  shorn  into  two  parts  by  such  instruments  as 
shears  or  scissors. 

Resilience  or   toughness  is   another  form   of   the   quality   of 


416  HANDBOOK    ON    ENGINEERING. 

strength ;  it  indicates  that  a  body  will  manifest  a  certain  degree 
of  flexibility  before  it  can  be  broken ;  hence,  that  body  which 
bends  or  yields  most  at  the  time  of  fracture  is  the  toughest. 

"Working  strength* —  The  term  "  working  strength  "  implies 
a  certain  reduction  made  in  the  estimate  of  the  strength  of  ma- 
terials, so  that  when  the  instrument  or  machine  is  put  to  use,  it 
may  be  capable  of  resisting  a  greater  strain  than  it  is  expected  on 
the  average  to  sustain. 

Safe  working  pressure,  or  safe  load*  —  The  safe  working  pres- 
sure of  steam-boilers  is  generally  taken  as  £  of  the  bursting  pres- 
sure, whatever  that  may  be. 

Strain  in  the  direction  of  the  grain,  means  strain  in  the  direc- 
tion in  which  the  iron  has  been  rolled ;  and  in  the  process  of  man- 
ufacturing boiler-plates,  the  direction  in  which  the  fibres  of  the 
iron  are  stretched  as  it  passes  between  the  rolls. 

Stress*  —  By  the  term  "  stress  "  is  meant  the  force  which  acts 
directly  upon  the  particles  of  any  material  to  separate  them. 

HEAT  AND  STEAM. 

The  steam  engine  is  a  machine  for  the  conversion  of  heat  into 
power  in  motion.  The  heat  is  generated  by  the  combustion  of 
fuel ;  the  transmission  is  accomplished  through  the  agency  of 
steam  ;  the  power  is  made  available  and  brought  under  control  by 
means  of  the  engine. 

The  effect  of  heat  upon  water  is  to  vaporize  it,  if  there  be  inten- 
sity enough,  the  heat  will,  under  proper  conditions,  cause  water  to 
boil ;  the  vapor  produced  by  boiling  is  called  steam,  and  steam 
under  pressure  is  a  product  which  is  the  end  and  aim  of  that  por- 
tion of  that  steam  engine  known  as  the  boiler  and  furnace.  The 
steam  engine  then  is  to  be  considered  as  a  form  of  the  heat 
engine ;  of  which  the  furnace,  boiler,  and  the  engine  itself  are  to 
be  regarded  as  separate  portions  of  the  same  mechanism. 


HANDBOOK    ON    ENGINEERING.  417 

The  conditions  demanded  .upon  economic  grounds  to  secure 
the  highest  efficiency  in  the  steam  engine  are :  — 

1.  A  proper  construction  of  the  furnace  so  as  to  secure  the 
perfect  combustion  of  fuel. 

2.  The  heat  generated  in  the  furnace  must  be  transferred  to  the 
water  in  the  boiler  without  loss. 

3.  The  circulation  in  the  boiler  must  be  so  complete  that  the 
heat  from  the  furnace  may  be  quickly  and  thoroughly  diffused 
throughout  the  whole  body  of  water. 

4.  The  construction  of  an  engine  that  will  use  the  steam  with- 
out loss  of  heat,  except  so  much  as  may  be  necessary  to  perform 
work  required  of  the  engine. 

5.  The  recovery  of  heat  from  exhaust  steam. 

6.  The  absence  of  friction  and  back  pressure  in  the  working  of 
the  engine. 

It  is  superfluous  to  say  that  these  conditions  are  not  fulfilled 
in  any  engine  of  the  present  day.  At  best  the  combustion  of 
fuel  is  only  approximately  perfect,  the  losses  being  due  to  several 
causes,  among  which  are,  -  unburned  fuel  falling  through  the 
spaces  in  the  grates  and  mingling  with  the  ashes.  This,  with 
.some  kinds  of  coal,  and  improper  firing,  amounts  to  a  large 
>  Tcentage  of  the  furnace  waste.  It  is  not  possible  with  any 
present  method  of  setting  boilers  to  transfer  all  the  heat  of  the 
furnace  to  the  water  in  the  boiler ;  nor  can  there  be,  for  the 
reason  that  the  temperature  of  the  escaping  gases  must  not  be 
lower  than  that  of  the  steam  in  the  boilers,  or  direct  loss  will  result 
in  the  radiation  of  heat  from  the  tubes  or  flues  in  the  boiler,  by 
MIS  reheating  the  gases  to  the  steam  temperature.  If  the  steam 
pressure  is  80  Ibs.  per  square  inch  above  the  atmosphere,  the  cor- 
responding temperature  due  to  this  pressure  is  324°  Fahr.  The 
temperature  of  the  escaping  gases  ought  not,  therefore,  to  be  less 
than  350°  Fahr.,  where  they  leave  the  boiler  flues  or  tubes  to  pass 
off  into  the  chimney.  If  the  temperature  of  the  furnace  be  taken 

27 


HANDBOOK    ON    ENGINEERING. 

. 

at  2,000°  Fahr.,  and  the  escaping  gases  at  400°  Fahr.,  it  will  be 
seen  that  one-fifth  of  the  heat  generated  in  the  furnace  is  passing 
off  without  performing  work.  This  is  a  very  great  loss,  and 
these  figures  understate,  rather  than  correctly  give,  the  loss  from 
this  one  source.  Efforts  have  been  made  to  utilize  the  tempera- 
ture of  these  waste  gases  by  making  them  heat  feed -water  by 
means  of  coils,  or  by  that  particular  disposition  of  pipes  and 
connection  known  as  an  economizer.  Others  have  turned  it  into 
account  by  making  it  heat  the  air  supplied  the  fuel  on  the  grates. 
Any  heat  so  reclaimed  is  money  saved,  provided  it  does  not  cost 
more  to  get  it  than  it  is  worth  in  coal  to  generate  a  similar  quan- 
tity of  heat.  It  is  doubtful  whether  the  loss  in  this  particular 
direction  can  be  brought  below  20  per  cent  of  the  fuel  burned,  at 
least,  by  any  method  of  saving  now  known. 

The  loss  by  bad  firing  and  by  a  bad  construction  of  furnace 
is  often  a  large  one.  It  has  been  demonstrated  experimentally 
that  20  to  30  per  cent  of  fuel  can  be  saved  by  a  proper  construc- 
tion and  operation  of  the  furnace.  The  direct  causes  of  loss  are, 
too  low  temperature  of  furnace  for  properly  burning  fuels,  espe- 
cially such  as  are  rich  in  hydro-carbon  gases ;  or,  by  the  admis- 
sion of  too  much  cold  air  over  or  back  of  the  fire ;  or,  by  the 
admission  of  too  little  air  under  the  fire  so  that  carbonic  oxide  gas 
is  generated  instead  of  carbonic  acid  gas,  the  former  being  a 
product  of  incomplete,  the  latter  the  product  of  complete 
combustion.  The  relative  heating  powers  of  fuel  burned,  resulting 
in  the  production  of  either  of  these  two  gases  being  as  follows :  - 

Heat  Units. 

1  pound  of  carbon  burned  to  carbonic  acid  gas  .     .      14,500 
1  pound  of  carbon  burned  to  carbonic  oxide  .     .     .       4,500 

Units  of  heat  lost  by  burning  to  carbonic  oxide       .    ^10,000 
It  will  be  seen  that  here  is  an  enormous  source  of  loss,  and  all 
that  is  required  to  prevent  it  is  a  proper  construction  of  furnace. 


HANDBOOK    ON    ENGINEERING.  419 

Smoke  is  a  nuisance  which  ought  to  be  prohibited  by  stringent 
legislation.  There  is  no  good  reason  for  its  polluting  presence  in 
the  atmosphere,  defiling  everything  with  which  it  comes  in  con- 
tact. Smoke  regarded  as  a  source  of  direct  loss  is  greatly  over- 
estimated ;  the  fact  is,  the  actual  amount  of  coal  lost  to  produce 
smoke  is  very  trifling.  The  presence  of  smoke  indicates  a  low 
temperature  of  furnace  or  combustion  chamber ;  if  the  temper- 
ature were  sufficiently  high  and  the  furnace  properly  constructed, 
smoke  could  not  be  generated.  The  prevention  of  smoke  is 
easily  accomplished,  and  with  it  a  more  economical  combustion 
of  hydro-carbon  fuels. 

Radiation*  —  A  considerable  loss  of  heat  occurs  by  radiation 
from  the  furnace  walls  ;  this  may  be  prevented  in  part  by  making 
the  walls  hollow,  with  an  air  space  between.  If  a  force  blast  is 
used  the  air  may  be  admitted  at  the  back  end  of  the  boiler  setting 
and  by  passing  through  between  the  walls  will  become  heated, 
and  if  conveyed  into  the  ash  pit  at  a  high  temperature  will  greatly 
assist  combustion  and  thus  tend  to  a  higher  economy. 

Air  required*  —  In  regard  to  the  quantity  of  air  required,  it 
will  vary  somewhat  with  the  fuel  used,  but  in  general,  12  pounds 
of  air  are  sufficient  to  completely  burn  one  pound  of  coal ;  prac- 
tically, however,  15  to  25  pounds  are  furnished,  being  largely  in 
excess  of  that  which  the  fire  can  use,  and  must  pass  off  with  the 
gases  as  a  waste  product.  This  surplus  air  enters  cold  and 
leaves  the  furnace  heated  to  the  same  temperature  as  that  of  the 
legitimate  and  proper  products  of  combustion,  and  thus  directly 
operates  to  the  lowering  of  the  furnace  temperature. 

Measurement  of  heat*  —  A  heat  unit  is  that  quantity  of  heat 
necessary  to  raise  the  temperature  of  one  pound  of  water  one 
degree,  from  39°  to  40°  Fahr.,  this  being  the  temperature  of  the 
greatest  density  of  water.  A  thermal  unit,  a  heat  unit,  or  unit 
of  heat,  all  mean  the  same  thing.  Experiments  have  been  made 
to  determine  the  mechanical  equivalent  of  a  heat  unit,  and  it  is 


420  HANDBOOK  ON  ENGINEERING. 

found  to  be  equal  to  778  pounds  raised  one  foot  high.  This  is 
sometimes  called  "Joule's  equivalent,"  after  Dr.  Joule,  of 
England  ;  it  is  also  known  as  the  dynamic  value  of  a  heat  unit. 
Knowing"  the  number  of  heat  units  in  a  pound  of  coal  enables 
us  to  calculate  the  amount  of  work  it  should  perform.  Let  us 
suppose  a  pound  of  coal  to  be  burned  to  carbonic  acid  gas, 
and  to  develop  during  its  combustion  14,000  heat  units,  then: 
14,000x778  equals  10,892,000  foot  pounds. 

That  is  to  say,  if  one  pound  of  coal  were  burned  under  the 
above  conditions  it  would  have  a  capacity  for  doing  work  repre- 
sented by  the  lifting  of  ten  millions  of  pounds  one  foot  high 
against  the  action  of  gravity.  Suppose  this  to  be  done  in  one 
hour,  then  we  should  expect  to  get  from  one  pound  of  coal  an 
equivalent  of  5.45  H.  P.  It  is  well  known  that  only  a  very 
small  fraction  of  such  equivalent  is  secured  in  the  very  best 
modern  practice.  The  question  is,  where  does  this  heat  go, 
and  why  is  it  so  small  a  portion  of  it  is  actually  utilized  ?  The 
losses  may  be  accounted  for  in  several  ways,  and,  perhaps,  as 
follows :  — 

The  heat  wasted  in  the  chimney     ....     25  per  cent. 

Through  bad  firing 10       " 

Heat  accounted  for  by  the  engine  (not  indicated)      10      " 
Heat  by  exhaust  steam 55       " 


100  per  cent. 

This  is  about  2  pounds  of  coal  per  hour  per  indicated  horse 
power,  which  is  regarded  as  a  very  high  attainment,  and  is 
seldom  reached  in  ordinary  cut-off  engines.  It  requires  good 
coal,  good  firing,  and  an  economical  engine  to  get  an  indicated 
horse  power  from  two  pounds  of  coal  burned  per  hour.  As 
coal  varies  in  quality  it  is  a  better  plan  to  deduct  the  ashes 
and  other  incombustible  matter,  and  take  the  net  combustible 
as  a  basis  of  comparison.  The  best  coal  when  properly  burned 


HANDBOOK    ON    ENGINEERING.  421 

is  capable  of  evaporating  12  pounds  of  water  from  and  at  a 
temperature  of  212°  Fahr.  The  common  evaporation  is  about 
half  that  amount,  and  with  the  best  improved  furnaces  and  care- 
ful management,  it  is  seldom  that  10  pounds  of  water  is  exceeded, 
and  is  to  be  regarded  as  a  high  rate  of  evaporation.  In  experi- 
mental tests,  12  pounds  have  been  reported,  but  it  is  doubtful 
whether  there  is  any  steam  boiler  and  furnace  which  is  con- 
stantly yielding  any  such  results. 

Circulation  of  water  in  a  boiler  is  a  very  important  feature  to 
secure  the  highest  evaporative  results.  Other  things  being  equal, 
the  boiler  which  affords  the  best  circulation  of  water  will  be  found 
to  be  the  most  economical  in  service.  Circulation  is  greatly  hin- 
dered in  some  boilers  by  having  too  many  tubes ;  in  others,  by 
introducing  in  the  water  space  of  the  boiler  too  many  stays  and 
making  the  water  spaces  too  narrow.  To  secure  the  highest 
economy  there  must  be  thorough  circulation  from  below  upwards, 
in  the  boiler.  There  is  no  doubt  that  a  great  deal  of  heat  is  lost 
because  the  construction  is  such  as  to  hinder  a  free  flow  of  water 
around  the  tubes  and  sides  of  the  boiler. 

The  construction  of  an  engine  that  will  use  steam  without  loss 
of  heat,  except  so  much  as  may  be  necessary  to  perform  work 
required  of  it,  is  a  physical  impossibility.  Among  the  sources  of 
loss  in  an  engine  are :  radiation,  condensation  of  steam  in  un- 
jacketed  cylinders,  and  the  enormous  loss  of  heat  occasioned  by 
exhausting  the  steam  into  the  atmosphere. 

Radiation  is  usually  classed  among  the  minor  losses  in  a  steam 
engine.  There  is  a  considerable  loss  of  heat  caused  by  radiation 
from  steam  boilers  and  pipes  exposed  to  the  atmosphere,  and  not 
protected  by  a  suitable  covering.  Much  of  this  heat  may  be 
saved  by  employing  a  non-conducting  material  as  a  covering, 
which,  though  not  preventing  all  radiation,  will  save  enough  heat 
to  make  its  application  economical.  It  is  well  known  that  some 
bodies  conduct  and  radiate  heat  less  rapidly  than  others,  but  it 


422  HANDBOOK    ON    ENGINEERING. 

must  not  be  understood  that  the  absolute  value  of  such  a  cover- 
ing is  inversely  proportioned  to  the  conducting  power  of  the 
material  employed,  because,  in  its  application,  the  outer  surface 
is  enlarged  and  the  radiation  will  be  going  on  less  actively  at  any 
given  point,  but  the  enlarged  surface  exposed  reduces  somewhat 
the  apparent  gain. 

SELECTION  OF  A  BOILER. 

The  selection  of  a  boiler  for  a  particular  service  will  naturally 
suggest  the  following  questions  :  — 

1 .  What  kind  of  a  boiler  shall  it  be  ? 

2.  Of  what  material  shall  it  be  made? 

3.  What  size  shall  it  be  in  order  to  furnish  a  certain  power? 
In  reply  to  the  first  question,  it  is  to  be  expected  there  will  be 

wide  differences  of  opinion,  varying  with  the  locality,  usage,  and 
service  for  which  it  is  intended.  One  of  the  first  things  to  be 
taken  into  account  in  the  selection  of  a  boiler  is  the  quality  of 
water  to  be  used  in  it  for  generating  steam.  If  the  water  is  pure, 
then  it  makes  little  difference  what  kind  of  boiler  be  selected,  so 
far  as  incrustation  affects  selection.  If  the  water  is  hard  and 
will  deposit  scale  upon  evaporation,  then  a  boiler  should  be 
selected  which  will  admit  of  thorough  inspection  and  removal  of 
any  deposit  formed  within  it. 

For  hard  water,  the  ordinary  flue  boiler  will  be  found  a  good 
one,  as  it  is  favorable  to  a  thorough  circulation  of  water,  and 
permits  easy  access  to  all  parts  of  it  for  examination  and  clean- 
ing. It  does  not,  however,  present  the  extent  of  heating  surface 
for  a  given  space  that  tubular  boilers  offer ;  but  with  hard  water 
the  boiler  is  quite  as  economical  if  kept  in  good  condition. 

The  difficulty  with  tubular  boilers  when  used  in  connection 
with  hard  water  is  that  the  tubes  will  in  a  short  time  become 
coated  with  scale ;  this  prevents  the  transmission  of  heat,  not 
only,  but  impairs  the  circulation  of  the  water  around  them. 


HANDBOOK    ON    ENGINEERING.  423 

Both  of  these  are  opposed  to  economy  in  the  fact  that  it  requires 
more  coal  to  generate  a  given  weight  of  steam  in  the  first  case  ; 
and  second,  by  reason  of  deficient  circulation  the  plates  over  the 
fire  are  likely  to  become  overheated  and  burnt  and  so  become 
dangerous ;  thus  directly  contributing  to  accident  or  disaster. 

The  matter  of  circulation  in  boilers  is  one  which  should  have 
careful  attention  in  making  a  selection.  There  is  little  trouble  in 
this  regard  with  any  of  the  ordinary  types  of  boilers  so  long  as 
they  are  clean  and  new,  and  properly  proportioned.  Nor  is  there 
likely  to  be  any  difficulty  thereafter  if  the  water  is  soft  and  clean. 
Circulation  is  often  seriously  impaired  by  putting  in  too  many 
tubes  in  a  boiler,  the  effect  of  which  is  to  so  fill  up  the  space  that 
the  heated  particles  of  water  forcing  their  way  upwards  from 
below  meet  with  so  much  resistance  that  they  can  hardly  over- 
come it,  and  the  result  is  that  a  boiler  does  not  furnish  from  one- 
fourth  to  one-half  as  much  steam  for  a  given  weight  of  fuel  as  it 
should,  from  this  very  cause. 

Boilers  intended  for  use  in  distant  localities  where  the  facilities 
for  repairs  are  meager  or  entirely  wanting,  and  fuel  low  priced, 
should  be  of  the  simplest  description.  Cylinder  boilers  or  two- 
flue  boilers  will  perhaps  be  found  most  suitable.  These  are 
largely  used  by  coal  miners,  blast  furnaces,  saw  mills,  and  other 
branches  of  industry,  which  must,  of  necessity,  be  removed  from 
the  larger  towns  and  engineering  work  shops. 

In  selecting  a  boiler  for  a  mill  of  any  kind  where  they  burn 
shavings  or  offal,  or  any  other  place  in  which  the  fuel  is  of 
a  similar  description  and  the  firing  irregular,  there  should  be 
large  water  capacity  in  the  boiler  that  it  may  act  as  a  reser- 
voir of  power  in  much  the  same  way  that  a  fly  wheel  acts  as 
a  regulator  for  a  steam  engine.  It  is  a  common  notion  among 
wood  workers  that  firing  with  shavings  or  light  fuel  is  "  easy 
on  the  boiler."  There  is  abundant  reason  to  doubt  this. 
The  suddenness  and  rapidity  with  which  an  intense  fire  is  kin- 


424  HANDBOOK    ON    ENGINEERING. 

died  in  the  furnace,  filling  all  the  furnace  space  and  the  tubes  with 
flame,  and  with  an  intense  heat  which  envelops  all  within  the  limits 
of  draft  opening,  continuing  thus  for  a  few  minutes  only,  and  as 
suddenly  going  out,  can  hardly  be  regarded  as  the  ideal  furnace. 
Yet  there  are  thousands  of  just  such  furnaces  at  work,  and  it  is 
altogether  probable  that  little  or  no  change  will  be  made  in  them 
by  this  class  of  manufacturers,  at  least  in  the  near  future.  In 
regard  to  the  selection  of  a  boiler  for  this  service,  we  are  brought 
back  again  to  the  question  of  hard  or  soft  water.  The  decision 
should  be  largely  influenced  by  this,  but  whatever  type  of  a  boiler 
is  selected  there  should  be  a  surplus  of  boiler  power  of  at  least  20 
per  cent,  that  is,  if  a  50  horse-power  boiler  is  needed  to  do  the 
Work,  put  in  one  of  60  horse-power ;  this  will  prevent  the  fluctua- 
tions of  speed  in  the  engine  which  are  sure  to  follow  a  reduction  of 
boiler  pressure. 

This  increase  in  boiler  power  ought  not  to  be  simply  that  of 
tube  surface,  but  should  also  include  extra  water  space.  The 
reserve  power  of  a  boiler  is  in  the  water  heated  up  to  a  temperature 
corresponding  to  the  steam  pressure ;  when  this  pressure  is 
lowered,  the  water  then  gives  off  steam  corresponding  to  the  lower 
pressure ;  the  more  water  the  more  steam ;  and  in  this  way  the 
water  in  the  boiler  stores  up  heat  when  overtired ,  to  give  it  off 
again  when  the  fire  is  low,  and  so  acts  a  regulator  of  pressure,  a 
thing  that  extra  tube  surface  cannot  do.  This  kind  of  firing  is 
apt  to  induce  priming,  and  for  this  reason  a  boiler  should  be 
selected  having  a  large  water  surface.  Horizontal  boilers  are,  in 
general,  to  be  preferred  over  vertical  ones  for  mills,  because  of  the 
larger  water  surface  exposed  in  proportion  to  the  heating  surface. 
If  a  tubular  boiler  is  selected,  the  water  line  above  the  tubes 
should  be  not  higher  than  two-thirds  the  diameter  of  the  boiler 
measured  from  the  bottom,  and  the  boiler  should  be  made  having 
the  upper  edge  of  the  top  row  of  tubes  at  least  three  inches  below 
this ;  there  should  also  be  a  clear  space  up  through  the  center  of 


HANDBOOK    ON    ENGINEERING. 

the  boiler  of  sufficient  width  to  insure  a  perfect  circulation  of 
water. 

Horizontal  tubular  boilers  are  to  be  recommended  when  pure 
soft  water  is  used.  They  combine  at  once  the  qualities  of  great 
strength  without  excessive  bracing,  large  heating  surface,  high 
evaporative  capacity  without  liability  to  priming,  and  are  conve- 
nient of  access  for  external  and  internal  examination  when  set  in 
the  furnace. 

Firebox  boilers,  or  locomotive  boilers,  as  they  are  commonly 
called,  are  best  adapted  for  small  powers  and  with  a  fuel  which 
deposits  but  little  soot  in  the  tubes.  This  kind  of  boiler  is  sup- 
plied with  portable  or  agricultural  engines  and  is  very  well  adapted 
for  that  particular  service.  In  canvassing  the  desirability  of 
this  kind  of  a  boiler  for  stationary  use,  we  must  again  refer  to  the 
kind  of  water  to  be  used  in  it.  If  the  water  is  soft  and  clean 
there  is  then  no  particular  objection  to  a  boiler  of  this  construc- 
tion being  used  for  small  powers  ;  if  the  water  is  hard  and  will 
form  scale,  it  ought  not  to  be  chosen,  but  a  flue  boiler  selected 
instead. 

Vertical  boilers  are  used  in  great  numbers  for  small  engines, 
heating,  etc.  They  have  the  merit  of  being  compact  and  low 
priced.  A  common  defect  in  the  construction  of  this  kind  of 
boiler  is  that  too  many  tubes  are  put  in  the  head  in  the  fire  box, 
thereby  preventing  a  proper  circulation  of  water  between  them. 
This  defect  in  construction  induces  priming,  with  all  its  attendant 
annoyances  and  dangers.  This  style  of  boiler  is  not  suited  to 
hard  water,  but  pure  soft  water  only.  These  boilers  should  be 
provided  with  hand  holes  above  the  crown  sheet  and  around  the 
bottom  of  the  water  legs ;  at  least  three  at  each  place  mentioned. 
In  regard  to  the  material  of  which  a  boiler  shall  be  made  there  is 
but  the  simple  choice  between  iron  and  steel. 

Steel  for  boilers  should  not  be  of  too  high  tensile  strength ; 
55,000  to  60,000  pounds  tensile  strength  per  square  inch  makes 


426  HANDBOOK    ON    ENGINEERING. 

the  best  boilers.  If  the  steel  is  of  too  high  a  grade  it  will  take  a 
temper,  and,  therefore,  is  utterly  unfit  for  use  in  steam  boilers ; 
if  the  steel  is  of  too  low  tensile  strength  it  is  apt  to  be  loose  or 
spongy.  Among  the  advantages  steel  possesses  over  iron  may  be 
mentioned  the  circumstance  that  it  is  a  practically  homogeneous 
material  when  properly  made  and  rolled,  consequently,  it  is  nearly 
as  strong  in  one  direction  as  it  is  in  another.  In  this  respect, 
steel  is  superior  to  iron  plate  of  equal  thickness,  because  the  latter 
is  made  up  of  several  pieces  of  iron  welded  together  and  in  rolling 
into  the  plate  it  becomes  fibrous,  and  thus  of  unequal  strength, 
being  greatest  in  the  direction  of  the  fiber,  and  least,  when  tested 
across  it. 

BOILER  TRIMMINGS. 


HANDBOOK   ON    ENGINEERING.  427 

lever  and  weight,  or  whether  it  be  fitted  with  a  spring.  The 
former  is  the  usual  manner  of  loading  a  safety  valve  and  has  but 
few  objections.  For  portable  engines  and  locomotives  safety 
valves  are  loaded  with  springs,  which  by  suitable  adjustment  may 
be  made  to  blow  off  at  any  desired  pressure. 

The  following  rule  is  that  enforced  by  the  U.  S.  Government 
in  fixing  the  area  of  safety  valves  for  ocean  and  river  service,  when 
the  ordinary  lever  and  weight  safety  valve  is  employed  :  — 

Rule*  —  When  the  common  safety  valve  is  employed  it  shall 
have  an  area  of  not  less  than  one  square  inch  for  each  two  square 
feet  of  grate  surface. 

Another  rule  is  to  multiply  the  pounds  of  coal  burned  per 
hour  by  4 ;  this  product  is  to  be  divided  by  the  steam  pressure, 
to  which  a  constant  number  10  is  added. 

EXAMPLE  :  What  would  be  the  proper  area  for  a  safety  valve 
for  a  boiler  having  a  grate  surface  5  feet  square  and  burning  12 
pounds  of  coal  per  hour  per  square  foot  of  grate ;  the  steam 
pressure  being  75  pounds  per  square  inch  ? 

5x5  equal  25  square  feet  of  grate. 

25  x  12  equal  300  Ibs.  of  coal  per  hour. 

300x4  equal  1200. 

75  plus  10  equal  85  equal  steam  pressure  with  10  added,  then 
1200  ~-  85  equal  14.11  inches  area,  or  4J  inches  diameter. 

A  feed  pipe  should  be  at  least  twice  the  area  over  that  which  is 
regarded  as  simply  necessary  to  supply  the  boiler  with  water,  as 
sediment  or  scale  is  likely  to  form  in  it,  which  will  materially  re- 
duce its  area.  In  localities  where  the  water  is  hard  the  feed 
pipes  should  be  disconnected  near  the  boiler  and  examined  occa- 
sionally to  ascertain  whether  or  not  scale  is  forming  in  them. 

In  general,  the  sizes  of  feed  pipes  leading  from  the  pump 
to  the  boiler  are  fixed  by  the  size  of  tap  used  by  the  maker  of 
the  pump.  It  is  not  well  to  reduce  the  diameter  of  the  pipe  and 
the  size  should  be  the  same  throughout.  Care  should  be 


428  HANDBOOK    ON    ENGINEERING. 

cised  in  putting  pipes  in  place  that  no  strain  be  brought  upon  them 
by  imperfect  fitting,  as  it  is  certain  to  lead  to  leaky  joints  at  some 
time  or  other.  It  is  also  desirable  that  the  pipes  be  as  short  and 
straight  as  possible.  Feed  pipes  should  never  be  placed  under 
ground  if  it  is  possible  to  make  any  different  disposition  of  them. 
In  locating  pipes  it  is  desirable  to  arrange  for  the  expansion  of 
the  boiler,  as  well  as  for  that  of  the  pipes  themselves.  In  select- 
ing a  pump  it  should  have  a  much  larger  capacity  than  that  needed 
to  supply  the  boiler,  as  there  are  many  things  which  affect  the 
working  of  a  pump,  such  as  a  defective  suction  pipe,  leaky  valves, 
etc.  It  is  the  practice  of  most  manufacturers  to  give  the  capacity 
of  their  pumps  in  gallons  of  water  delivered  per  minute,  from 
which  it  is  easy  to  select  a  suitable  size  ;  but  the  speed  given  in 
the  tables  at  which  the  pump  is  to  run  is  generally  faster  than 
that  which  it  is  desirable  to  run  them.  As  a  general  thing,  and 
without  referring  to  any  particular  maker  or  design,  it  is  a  good 
plan  to  select  a  pump  having  four  times  the  capacity  actually 
needed  for  the  boiler ;  then  the  speed  may  be  reduced  to  half  that 
given  in  the  table,  and  will  require  less  repairs,  and  will  be  a  more 
satisfactory  purchase  in  the  long  run. 

In  selecting  an  injector  or  inspirator,  the  size  should  not 
greatly  exceed  that  actually  required  to  supply  the  boiler.  In 
making  the  steam  connections  the  pipes  should  start  from  the 
steam  space  of  the  boiler  and  should  not  be  branches  merely  from 
the  other  steam  pipes ;  neither  should  the  diameters  of  the  pipes 
be  less  than  that  which  the  instrument  calls  for.  The  pipes 
should  be  as  short  and  straight  as  practicable ;  abrupt  bends 
should  always  be  avoided  in  the  suction  pipes.  If  the  water  is 
taken  from  a  place  in  which  there  are  floating  particles  of  wood, 
leaves,  etc.,  a  strainer  should  be  used;  a  large  sheet  metal  box 
with  perforated  sides,  makes  a  good  strainer ;  the  openings  ought 
not  too  greatly  exceed  an  eighth  of  an  inch  in  diameter,  and  should 
be  several  times  the  area  of  the  suction  pipe. 


HANDBOOK    ON    ENGINEERING.  429 

A  check  valve  should  be  fitted  with  a  valve  between  it  and  the 
boiler,  so  that  in  the  event  of  its  not  working  satisfactorily  it  may 
be  taken  apart,  cleaned  and  replaced  without  stopping  for  exami- 
nation or  repairs. 

The  blow-off  pipe  should  be  so  arranged  that  it  will  entirely 
drain  the  boiler  of  water ;  it  is  also  a  good  plan  to  set  a  boiler 
with  a  slight  inclination  toward  the  blow-off  pipe  that  it  may  be 
thoroughly  drained ;  an  inclination  of  two  inches  in  twenty  feet 
works  well  in  practice.  The  blow-off  pipe  is  usually  fitted  at  the 
back  end  of  the  boiler. 

The  steam  pipe  may  be  connected  at  any  convenient  point  on 
the  top  of  the  boiler.  If  the  boiler  is  to  furnish  steam  for  an 
engine  only,  the  common  practice  is  to  make  the  diameter  of  the 
pipe  one-fourth  that  of  the  cylinder.  The  steam  pipe  should  be 
as  short  and  straight  as  possible.  If  bends  are  to  be  introduced 
in  steam  pipes  it  is  better  to  have  a  long  curved  bend  than  the 
abrupt  right-angle  fitting  usually  employed  for  the  purpose.  It 
is  also  a  good  plan  to  provide  a  stop-valve  next  to  the  boiler  to 
shut  off  the  steam  and  prevent  it  condensing  in  the  steam  pipe  at 
night,  or  other  long  stoppages. 

The  gauge  cocks  should  not  be  less  than  three  in  number,  and 
may  be  of  any  of  the  various  kinds  now  in  the  market.  For 
stationary  boilers,  the  Mississippi  gauge  cock  is,  perhaps,  as 
good  as  any.  For  portable  engines  a  compression  gauge-cock  is, 
perhaps,  the  best.  The  lower  gauge-cock  should  be  at  least 
2"  above  the  tubes  or  crown  sheet,  the  middle  2"  above  the  first 
ordinary  water  line,  the  upper  2"  to  3"  above  the  second,  de- 
pending on  the  size  of  the  boiler. 

A  glass  water  gauge  should  be  provided  for  each  boiler  and 
should  be  so  located  that  the  water  level  in  the  boiler  when  at  the 
lower  end  of  glass  shall  be  one  inch  above  the  top  of  flue.  When 
glass  gauges  are  so  fitted  the  fireman  can  always  tell  at  a  glance 
just  how  much  water  he  has  above  the  flues  or  crown  sheet ;  it 


430  HANDBOOK    ON    ENGINEERING. 

also  permits  the  easy  test  of  accuracy  by  trying  the  gauge-cocks 
with  the  water  at  a  certain  known  level.  Too  much  dependence 
must  not  be  placed  on  the  glass  water-gauge  alone,  but  should  be 
used  in  connection  with  the  gauge-cocks. 

A  steam  gauge  is  a  very  important  appendage  to  a  steam 
boiler,  and  should  be  chosen  with  special  reference  to  accuracy 
and  durability.  The  ordinary  gauges  now  in  the  market  are  the 
bent  tube  and  the  diaphragm  gauges.  It  matters  little  which  of 
the  two  kinds  is  selected,  provided  it  is  a  good  and  first-class 
gauge.  A  steam  gauge  should  be  compared  with  a  standard  test 
gauge  at  least  once  a  year,  to  see  that  it  is  correct.  The 
importance  of  this  will  be  fully  apparent  when  it  is  known  that  it 
furnishes  the  only  means  by  which  the  fireman  is  to  judge  of  the 
steam  pressure  in  the  boiler.  A  siphon  should  be  attached  to 
every  gauge,  and  provision  should  also  be  made  for  draining  the 
gauge  or  siphon,  to  prevent  freezing  when  steam  is  off  the  boiler. 
Neglect  of  this  may  endanger  the  accurate  reading  of  the  steam 
gauge  and  render  it  useless. 

Steam  dome*  —  This  is  a  reservoir  for  steam  riveted  to  the 
upper  portion  of  the  shell  and  communicated  by  a  central  opening 
with  the  steam  space  in  the  boiler.  When  this  reservoir  forms  a 
separate  fixture  and  is  attached  to  the  boiler  by  cast  or  wrought 
iron  nozzles,  it  is  then  called  a  steam  drum.  The  latter  answers 
all  the  purposes  for  stationary  boilers  that  the  former  does,  and 
is  to  be  preferred  because  of  the  smaller  openings  in  the  shell  of 
the  boiler.  A  considerable  number  of  boiler  explosions  have 
been  traced  directly  to  the  weakness  of  the  shell,  caused  by  the 
large  opening  in  and  imperfect  staying  of  the  shell  underneath 
the  dome.  When  a  dome  is  employed  and  has  a  large  hole  under- 
neath, the  strength  of  the  shell  is  impaired  in  two  ways:  1.  By 
reducing  the  longitudinal  sectional  area  of  shell  through  the  cen- 
ter of  opening  cut  for  it,  which  weakness  cannot  wholly  be  made 
good  by  a  strengthening  ring  around  the  opening.  2.  By  causing 


HANDBOOK    ON    ENGINEERING.  431 

a  tension  equal  to  that  on  the  crown  area  of  steam  dome,  upon 
the  annular  part  of  the  shell  covered  by  the  flange  of  the  dome. 
The  weakest  part  of  the  boiler  shell  will  be  where  the  distance 
from  rivet  hole  at  the  base  of  the  dome  to  edge  of  plate  is  least. 
It  is  difficult,  owing  to  the  complex  nature  of  the  strains,  to  form 
a  rule  whereby  to  determine  how  much  the  strength  of  the  shell 
is  impaired  by  using  a  dome ;  but  it  is  quite  apparent  from  gen- 
eral experience  that  they  are  in  many  cases  a  source  of  weakness, 
and  the  larger  the  dome  connection  with  the  shell,  the  greater  the 
liability  to  rupture.  This  tendency  to  rupture  is  due  to  the  fact 
that  the  dome,  with  its  connecting  flange,  is  practically  inelastic ; 
that  portion  of  the  shell  of  the  boiler  covered  by  the  dome  is,  as 
soon  as  the  pressure  is  introduced  on  both  sides  of  the  plate, 
simply  a  curved  brace.  The  pressure  of  the  steam  in  the  boiler 
has  a  tendency  to  straighten  the  shell  under  the  dome  and  thus 
brings  about  a  series  of  complex  strains, which  are  not  easily  rem- 
edied by  any  system  of  bracing,  so  that  on  the  whole  it  is  prefer- 
able to  use  a  small  connecting  nozzle  with  a  drum  above  it,  rather 
than  to  rivet  a  large  dome  directly  to  the  shell. 

Dry  pipe*  —  This  is  a  pipe  having  numerous  small  perforations 
on  its  upper  side,  and  inserted  in  the  upper  part  of  the  steam  space 
of  the  boiler.  This  pipe  does  not  dry  the  steam,  but  acts 
mechanically  by  separating  the  steam  from  the  water  when  the 
latter  is  in  a  violent  state  of  agitation,  and  is  liable  to  be  carried 
in  bulk  toward  or  into  the  steam  pipe.  The  object  of  these  numer- 
ous small  holes  in  the  pipe  is  that  a  small  quantity  of  steam  may 
be  taken  from  a  large  number  of  openings  at  one  time,  and  thus 
carried  over  a  larger  extent  of  surface  than  that  afforded  by  a 
single  opening,  and  by  this  single  device  checking  the  tendency  to 
priming. 

Steam  boiler  furnaces  are  receiving  more  attention  now  than 
perhaps  ever  before.  The  question  of  economy  of  fuel  is  being 
closely  studied,  and  there  is  now  an  effort  to  save  much  of  the 


432  HANDBOOK  ON  ENGINEERING. 

heat,  which  had  formerly  been  allowed  to  go  to  waste.  The  main 
thing  in  furnace  construction  is  to  get  perfect  combustion.  With- 
out this  there  must  be  of  necessity  a  great  loss  constantly  going 
on.  There  are  some  losses  which  it  is  difficult  to  prevent,  for 
example  —  the  loss  by  the  admission  of  too  much  air  in  the  ash 
pit ;  the  loss  by  incomplete  combustion ;  the  loss  occasioned  by 
the  heated  gases  escaping  up  the  chimney ;  the  loss  by  radia- 
tion ;  but,  chief  among  these,  is  that  of  incomplete  combustion. 
To  burn  a  pound  of  coal  requires  about  twenty-four  pounds  of  air, 
or,  say  300  cubic  feet.  Most  boiler  settings  permit  from  200  to  300 
feet  to  pass  through  the  fire.  It  is  needless  to  point  out  the 
great  source  of  loss  arising  from  this  one  cause  alone.  This  may 
be  prevented  in  a  measure  by  having  a  suitable  damper  in  the 
chimney,  and  regulating  the  flow  of  escaping  gases  by  it,  instead 
of  the  ash  pit  doors.  If  the  furnace  is  so  constructed  that  the 
fuel  is  imperfectly  burned,  so  that  carbonic  oxide  instead  of  car- 
bonic acid  gas  is  formed,  the  loss  is  very  great.  This  results 
often  from  too  little  air  supply  and  too  low  temperature  in  the 
furnace.  The  furnace  doors  should  be  provided  with  an  opening 
leading  into  the  space  between  the  door  proper  and  the  liner ; 
this  opening  ought  to  have  a  sliding  or  revolving  register  by  which 
the  admission  of  air  may  be  controlled.  By  this  means,  the 
quantity  of  air  admitted  above  the  fire  may  be  adjusted  to  its 
needs  by  a  little  attention  on  the  part  of  the  fireman.  The  liner 
to  the  furnace  door  should  have  a  number  of  small  holes  in  it, 
rather  than  a  solid  plate,  with  a  space  around  the  edges.  Great 
care  should  be  exercised  in  the  construction  of  furnace  walls, 
that  the  materials  and  workmanship  be  good  throughout.  The 
entire  structure  should  be  brick.  The  outer  walls  may  be  of 
good  hard  red  brick,  but  the  interior  walls,  around  the  furnace 
and  bridge  wall,  should  be  of  fire  brick.  The  best  quality  of  fire 
brick  for  withstanding  an  intense  heat  are  very,  very  strong  and 
tenacious ;  the  structure  is  open  and  they  are  free  from  black 


HANDBOOK    ON    ENGINEERING.  433 

spots,  due  to  sulphuret  of  iron  in  the  clay ;  if  well  burned  they 
will  not  be  very  light  colored  on  the  outside,  and  will  have  a 
clear  ring  when  struck. 

Fire  brick  should  be  dipped  in  a  thin  mortar  made  of  fire  clay, 
rather  than  in  a  lime  and  sand  mortar,  such  as  is  used  in  ordinary 
red  brickwork.  In  laying  up  these  portions  of  a  boiler  furnace 
requiring  fire  brick,  provision  should  be  made  in  the  original  wall 
for  replacing  the  fire  brick  and  without  disturbing  the  outer 
brickwork. 

CARE  AND  MANAGEMENT  OF  A  BOILER. 

It  is  not  enough  that  a  boiler  be  of  approved  design,  made  of 
the  best  materials,  and  put  together  in  the  best  manner ;  that  it 
have  the  best  furnace  and  the  most  approved  feed  and  safety 
apparatus.  These  are  all  desirable,  and  are  to  be  commended, 
but  cleanliness  and  careful  management  are  quite  essential  to  get- 
ting high  results,  and  are  also  conducive  to  long  use  in  service. 

Pumps*  —  Special  attention  should  be  given  at  all  times  to  the 
feed  and  safety  apparatus ;  the  pumps  should  be  in  good  working 
order ;  it  is  preferable  that  they  be  independent  steam  pumps 
rather  than  pumps  driven  by  the  engine,  or  by  a  belt ;  they  should 
be  kept  well  packed  and  the  valves  in  good  condition. 

Firing*  —  Kindle  a  fire  and  raise  steam  slowly  ;  never  force  a 
fire  so  long  as  the  water  in  the  boiler  is  below  the  boiling  point. 
The  fire  should  be  of  an  even  height,  and  of  such  a  thickness  as 
will  be  found  best  for  the  particular  fuel  to  be  burned,  but  should 
be  no  thicker  than  actually  necessary.  In  regard  to  the  size  of 
coal  used,  that  will  depend  upon  circumstances.  If  anthracite 
coal  is  used,  it  should  not,  for  stationary  boilers,  be  larger  than 
ordinary  stove  coal.  For  bituminous  coal,  which  is  always  shipped 
in  lumps  as  large  as  can  be  conveniently  handled,  the  size  will 
vary  somewhat  in  breaking,  but  it  may  in  general  be  used  in 
larger  lumps  than  anthracite.  If  the  coal  is  likely  to  cake  in  burn- 

28 


434  HANDBOOK    ON    ENGINEERING. 

ing,  the  fire  should  be  broken  up  quite  frequently  with  a  slice  bar, 
or  it  will  fuse  into  a  large  mass  in  the  center  of  the  furnace  and 
lower  the  rate  of  combustion.  If  the  coal  is  likely  to  form  a  con- 
siderable quantity  of  clinker,  or  enough  to  become  troublesome,  it 
may  be  advantageous  to  increase  the  grate  area  and  thus  lower 
the  rate  of  combustion  per  square  foot  of  grate,  and  have  a  fire  of 
less  intensity.  The  fire  should  be  kept  free  from  ashes,  and  the 
ash  pit  should  be  kept  clean.  Whenever  the  fire  door  of  a  steam 
boiler  furnace  is  opened,  the  damper  should  be  closed  to  prevent 
the  sudden  reduction  of  temperature  underneath,  which  is  likely 
to  injure  the  boiler  by  contraction,  and  thus  render  it  likely  to 
spring  a  leak  around  the  riveted  joints.  Some  firemen  are  very 
careless  in  this  respect,  and  there  is  little  doubt  that  many  a  dis- 
agreeable job  of  repairing  a  leaky  seam  might  be  prevented  by 
this  simple  precaution. 

Gauge  cocks  should  be  used  constantly  to  keep  them  free  from 
any  accumulation  of  sediment.  It  is  a  very  common  practice  to 
rely  wholly  on  the  indications  of  the  glass  water  gauge  for  the 
water  level  in  the  boiler.  This  is  all  wrong  and  should  be  dis- 
continued, if  once  begun.  The  glass  water  gauge  serves  a  very 
useful  purpose,  but  it  should  not  be  wholly  relied  on  in  practice. 
In  using  the  ordinary  gauge  cocks,  the  ear  more  than  the  eye, 
detects  the  water  level,  and  thus  acts  as  a  check  on  the  indications 
given  by  the  glass  gauge. 

Water  gauges  should  be  tested  several  times  during  the  day  to 
see  that  they  are  clear,  and  to  keep  them  free  from  any  sediment 
likely  to  form  around  the  lower  opening  to  the  water  in  the 
boiler.  If  this  is  not  attended  to,  the  water  gauge  is  likely  to 
indicate  a  wrong  water  level  and  a  serious  accident  may  be  the 
result. 

Steam  or  pressure  gauges  are  likely  to  become  set  after  long 
use  and  should  be  tested  at  least  once,  or  better  still,  twice  a  year 
by  a  standard  gauge  known  to  be  correct.  They  should  also  be 


HANDBOOK    ON    ENGINEERING.  435 

tested  every  few  days  if  the  boilers  are  constantly  under  steam 
by  turning  off  the  steam  and  allowing  the  pointer  to  run  back  to 
zero.  If  there  are  two  or  more  boilers  set  together  in  one  battery, 
and  each  boiler  has  its  own  steam  gauge,  and  which  will,  starting 
from  the  zero  point,  indicate  the  same  pressure  on  all  the  gauges, 
they  may  be  assumed  to  be  correct. 

Blow-off  cocks  or  valves  should  be  examined  frequently  and 
should  never  be  allowed  to  leak.  In  general  a  cock  is  to  be  pre- 
ferred to  a  valve,  but  both  is  safer  than  one ;  if  the  latter  is 
selected  it  should  be  some  one  of  the  various  u  straight- way 
valves,"  of  which  there  are  now  several  in  the  market.  If  the 
cock  is  a  large  one,  and  especially  if  it  has  either  a  cast  iron  shell 
or  plug,  it  should  be  taken  apart  after  each  cleaning  out  of  the 
boilers,  examined,  greased  with  tallow  and  returned. 

Blowing  out*  —  This  should  be  done  at  least  once  a  day, 
except  in  the  very  rare  instances  in  which  water  is  used  that  will 
not  form  a  scale.  The  water  should  not  be  let  out  of  a  boiler  or 
boilers  until  the  furnace  is  quite  cold ,  as  the  heat  retained  in  the 
walls  is  likely  to  injure  an  empty  boiler  directly  by  overheating 
the  plates,  and  indirectly  by  hardening  the  scale  within  the 
boiler.  Bad  effects  are  likely  to  follow  when  a  boiler  is  emptied 
of  its  water  before  the  side  walls  have  become  cool ;  but  greater 
injury  is  likely  to  result  when  cold  water  is  pumped  into  an  empty 
boiler  heated  in  this  manner.  The  unequal  contraction  of  the 
boiler  is  likely  to  produce  leaky  seams  in  the  shell  and  to  loosen 
the  tubes  and  stays.  It  is  a  better  plan  to  allow  the  boiler  to 
remain  empty  until  it  is  quite  cold,  or  sufficiently  reduced  in  tem- 
perature to  permit  its  being  filled  without  injury.  Many  boilers 
of  good  material  and  workmanship  have  been  ruined  by  the 
neglect  of  this  simple  precaution. 

Fusible  plugs  should  be  carefully  examined  every  six  months, 
as  scale  is  likely  to  form  over  the  portion  projecting  into  the 
water  space.  It  is  only  a  question  of  time  when  this  scale 


436  HANDBOOK    ON    ENGINEERING. 

would  form  over  the  end  of  the  plug,  and  thick  enough  to  with- 
stand the  pressure  of  steam  and  thus  fail  in  the  accomplishment  of 
the  very  object  for  which  it  was  introduced.  This  applies  espe- 
cially to  the  fusible  plugs  inserted  in  the  crown  sheets  of  portable 
engine  boilers. 

Cleaning  tubes*  —  This  should  be  done  every  day  if  bitumin- 
ous coal  is  used.  A  portable  steam  jet  will  be  found  an  extremely 
useful  contrivance  which  will  keep  them  reasonably  clean  by  blow- 
ing out  the  loose  soot  and  ashes  deposited  in  the  tubes.  Every 
two  or  three  days,  or  at  least  once  a  week,  a  tube  scraper  or  stiff 
brush  should  be  used  to  take  out  all  the  ashes  or  soot  adhering 
to  the  tubes  and  which  cannot  be  blown  out  with  the  jet.  Flues 
may  be  cleaned  the  same  way  but  will  not  require  to  be  done  so 
frequently. 

Low  water*  —  If  from  any  cause  the  water  gets  low  in  the 
boiler,  bank  the  fire  with  ashes  or  with  fresh  coal  as  quickly  as 
possible,  shut  the  damper  and  ash  pit  doors  and  leave  the  fire 
doors  wide  open ;  do  not  disturb  the  running  of  the  engine  but 
allow  it  to  use  all  the  steam  the  boiler  is  making;  do  not 
under  any  circumstances  attempt  to  force  water  in  the  boiler. 
After  the  steam  is  all  used  and  the  boiler  cooled  sufficiently  to  be 
safe,  then  the  water  may  be  admitted  and  brought  up  to  the  reg- 
ular working  height ;  the  damper  opened  and  the  fires  allowed  to 
burn  and  steam  raised  as  usual;  provided,  no  injury  has  been 
done  the  boiler  by  overheating. 

Foaming  and  priming  are  always  troublesome  and  often  danger- 
ous. Some  boilers  prime  almost  constantly,  because  of  their  bad 
proportion,  and  will  require  the  constant  care  of  the  person  in 
charge,  especially  at  such  times  as  the  engine  may  be  using  the 
steam  up  to  the  full  capacity  of  the  boiler.  In  a  case  of  this  kind, 
an  increase  in  pressure  will  often  check,  but  will  not  entirely 
prevent  it ;  nothing  short  of  an  increase  of  water  surface,  or  a 
better  circulation  of  water,  or  a  larger  steam  room  will  afford  a 


HANDBOOK    ON    ENGINEERING.  437 

complete  remedy.  If  the  foaming  or  priming  is  due  to  a  sudden 
liberation  of  steam,  or  on  account  of  impure  feed  water  it  may  be 
checked  by  closing  the  throttle  valve  to  the  engine  and  opening 
the  fire  door  for  a  few  minutes.  The  surface  blow  may  be  used 
with  advantage  at  this  time,  by  blowing  off  the  impurities  collected 
on  the  surface  of  the  water.  The  feed  pump  may  be  used  if 
necessary,  but  care  should  be  exercised  that  too  much  cold  water 
be  not  forced  into  the  boiler,  and  thus  lose  time  by  having  to 
wait  for  the  accumulation  of  the  regular  steam  pressure  required 
for  the  engine.  The  dangers  attending  foaming  or  priming  are : 
the  laying  bare  of  heating  surfaces  in  the  boiler,  and  of  breaking 
down  the  engine  by  working  water  into  the  cylinder.  The  com~ 
monest  damage  to  the  engine  being  either  the  breaking  of  a  cylin- 
der head,  or  the  cross-head,  or  the  breaking  of  the  piston.  Wbeu 
boilers  are  new  and  set  to  work  for  the  first  time  priming  is  a  very 
frequent  occurrence ;  in  fact,  it  may  be  said  that  for  the  first  few 
days  there  is  always  more  or  less  of  it.  All  that  is  needed  during 
this  time  is  a  little  care  on  the  part  of  the  attendant  to  see  that 
the  water  is  kept  up  to  the  required  level  in  the  boiler ;  it  is  also 
recommended  that  the  throttle  valve  to  the  engine  be  partially 
closed  to  prevent  any  very  great  variation  of  pressure  in  the 
boiler,  and  thus  prevent  water  passing  over  with  the  steam 
in  such  quantities  as  to  become  dangerous.  If  a  boiler 
continues  to  prime*  after  it  has  had  a  weeR's  work  and 
then  thoroughly  cleaned,  the  causes  are  to  be  attributed  to 
other  than  the  grease  and  dirt  in  it,  which  are  inseparable  from 
the  manufacture.  As  already  said,  priming  may  be  caused  by  a 
sudden  reduction  of  pressure ;  that  is,  a  boiler  may  be  working 
smoothly  and  well  with,  say,  80  pounds  pressure ;  if  an  increase 
of  load  be  suddenly  applied  to  an  engine  so  as  to  reduce  the 
pressure  to  70  or  60  pounds,  this  sudden  reduction  of  pressure 
will  almost  always  cause  priming ;  the  less  the  steam  space  in  the 
boiler,  the  greater  the  tendency  to  prime,  and  the  greater  the 


438  HANDBOOK    ON    ENGINEERING. 

difficulty  in  checking  it.  The  only  permanent  cure  for  this  is 
more  boiler  power ;  as  a  temporary  expedient,  the  engine  should 
be  throttled  sufficiently  to  make  the  drain  upon  the  boiler  con- 
stant instead  of  intermittent.  If  the  duty  required  of  an  engine 
is  irregular,  the  steam  pressure  should  be  carried  higher ;  in  any 
case  similar  to  the  above,  it  is  recommended  that  the  pressure  be 
increased  to  90  or  100  pounds  and  the  throttling  to  begin  with 
the  increased  drain  upon  the  boiler.  But  this  is  at  best  a  mere 
makeshift,  and  a  larger  boiler  power  becomes  imperative  both 
on  the  score  of  economy  and  safety. 

WATER  FOR  USE  IN  BOILERS. 

Water  is  never  pure,  except  when  made  so  in  a  laboratory  or 
by  distillation  ;  the  impurities  may  be  divided  into  four  classes : 
1.  Mechanical  impurities.  2.  Gaseous  impurities.  3.  Dissolved 
mineral  impurities.  4.  Organic  impurities. 

(a)  Mechanical  impurities  may  be    both  mineral  and  organic. 
The  commonest  suspended  impurity  in  water  is  mud  or  sand ; 
these  may  be  removed   by  filtration  or  by  allowing  the  water  to 
stand  long  enough  to  let  them  settle  to  the  bottom  of  the  tank  or 
cistern  and  then   carefully  drawing  the  water  from  the  top,  and 
without  disturbing  the  bottom. 

(b)  Gaseous  impurities  in  water  vary  somewhat  according  to  the 
localities  from  which  they  are  obtained.     The  commonest  gases 
found  in  the  water  are  an  excess  of  oxygen,  nitrogen  and  carbonic 
acid.     These  have  no  effect  on  water  intended  for  steam  boilers. 

(c)  Dissolved   mineral   impurities  in   water   are  of  the   most 
varied  description,  and  are  almost  always  found  in  it.     Among 
these  are  found  salts  of  iron,  sulphate  and  carbonates  of  lime ; 
sulphate  and  carbonates  of  magnesia ;   salt  and  alkalies,  such  as 
soda,   potash,    etc. ;  acids,  such   as    sulphuric,  phosphoric,  and 
others.     All  of  these  are  more  or  less  injurious  to  steam  boilers. 
The  most  objectionable  are  the  salts  of  lime  and  magnesia,  which 
impart  to  water  that  property  known    as  hardness.     When  such 


HANDBOOK    ON    ENGINEERING.  439 

water  is  used  in  a  steam  boiler  a  scale  will  gradually  form,  which 
will,  in  a  short  time,  become  very  troublesome. 

(d)  Organic  impurities  are  present,  to  a  certain  extent,  in 
most  waters.  They  are  sometimes  present  in  the  water  in  suffi- 
cient quantities  to  give  it  a  very  decided  color  and  taste. 

The  presence  of  organic  matter  in  water  is  often  dangerous  to 
health,  and  may  be  a  means  of  spreading  contagious  diseases, 
but  has  little  or  no  bad  effect  in  any  water  used  for  steam  boilers. 
In  general,  water  is  regarded  by  engineers  as  being  either  soft, 
hard  or  salt. 

Ebullition  is  the  motion  produced  in  a  liquid  by  its  rapid 
conversion  into  vapor.  When  heat  is  applied  to  the  bottom  of  a 
boiler,  the  particles  of  water  in  contact  with  the  plates  become 
heated  and  immediately  expand,  and  becoming  specifically  lighter, 
pass  upwards  through  the  colder  body  of  water  above  ;  the  heat  of 
the  furnace  is  in  this  way  diffused  throughout  the  whole  body  of 
water  in  the  boiler  by  a  translation  of  the  particles  of  water  from 
below  upwards,  and  from  top  to  bottom  in  regular  succession. 
After  a  time  this  liquid  mass  becomes  heated  to  a  degree  in  which 
there  is  a  violent  agitation  of  the  whole  body  of  water,  steam  is 
given  off  and  it  is  said  to  boil.  The  temperature  at  the  boiling 
point  of  water,  at  ordinary  atmospheric  pressure,  is  212°  Fahr., 
and  increases  as  the  pressure  of  steam  above  it  increases. 

Distilled  water  for  boilers  is  not  to  be  recommended  without 
some  reservation.  Chemically  pure  water,  and  especially  water 
which  has  been  redistilled  several  times,  has  a  corrosive  action  on 
iron  which  is  often  very  troublesome.  The  effect  on  steel  plates 
by  the  use  of  water  several  times  redistilled,  such,  for  example,  as 
that  supplied  for  heating  buildings,  is  well  known  ;  information  is 
yet  wanting  which  shall  point  with  certainty  to  the  exact  change 
which  the  water  undergoes  and  explain  why  its  action  on  or 
affinity  for  steel  is  so  greatly  intensified.  It  has  been  suggested 
as  a  means  of  neutralizing  this  corrosive  action  of  the  water,  to 


440  HANDBOOK    ON    ENGINEERING. 

introduce  with  the  feed  other  water,  which  shall  have  the  prop- 
erty of  forming  a  scale  and  continuing  it  long  enough  and  at  such 
intervals  as  will  permit  the  formation  of  a  thin  scale  in  the  interior 
of  the  boiler.  However  objectionable  this  may  seem  at  first 
sight,  it  is  at  present  the  best  practical  solution  of  the  difficulty. 

Scale  is  a  bad  conductor  of  heat  and  is  opposed  to  economical 
evaporation.  It  is  estimated  that  a  thickness  of  half  an  inch  of 
hard  scale  firmly  attached  to  a  boiler  plate  will  require  a  temper- 
ature of  about  700°  Fahr.  in  the  boiler  plate  in  order  to  raise  and 
maintain  an  ordinary  steam  pressure  of  75  pounds.  The  mis- 
chievous effects  of  accumulated  scale  in  the  boiler,  especially  in 
the  plates  immediately  over  the  fire,  are :  (1)  preventing  the  water 
from  coming  in  contact  with  the  plates,  and  thus  directly  con- 
tributing to  the  overheating  of  the  latter;  and  (2)  by  causing  a 
change  of  structure  in  the  plates  and  the  consequent  weakening 
brought  about  by  this  continual  overheating,  which  would,  in  a 
short  time,  render  an  iron  or  a  steel  plate  wholly  unfit  for  use  in 
a  steam  boiler.  The  two  principal  ingredients  in  boiler  scale  are 
lime  and  magnesia.  The  lime,  when  in  combination  with 
carbonic  acid,  forms  carbonate  of  lime  ;  when  in  combination  with 
sulphuric  acid,  it  then  becomes  sulphate  of  lime.  This  is  also 
true  of  magnesia. 

Carbonate  of  lime  will  form  in  the  boiler  as  a  loose  powder, 
which  is  held  mechanically  in  suspenion ;  while  in  this  stage  it 
may  be  blown  out  of  the  boiler  without  injury  to  it ;  but  it  is 
seldom  that  a  pure  carbonate  is  formed  in  the  boiler  as  there  are 
other  impurities  in  the  water  with  which  it  combines  to  form  a 
hard  scale.  This  is  especially  true  in  such  waters  as  also  contain 
sulphate  of  lime  in  solution.  This  fine  powder  (carbonate  of 
lime),  will  form  a  hard  scale  should  any  adhere  to  the  sides  or 
bottom  of  a  boiler ;  in  any  case  where  the  boiler  is  blown  out  dry 
while  the  furnace  walls  are  still  hot;  and  this,  in  itself,  forms  an 
excellent  reason  why  boilers  should  stand  until  the  furnace  walls 


HANDBOOK    ON    ENGINEERING.  441 

are  cold  before  blowing  out.  When  emptied,  nearly  or  all  of  this 
slushy  deposit  may  be  washed  out  of  the  boiler  by  means  of  a 
hose. 

Sulphate  of  lime  is  not  so  easily  got  rid  of,  as  it  is  heavier  than 
carbonate  of  lime  and  adheres  to  the  plates  while  the  boiler  is  at 
work.  It  is  the  most  troublesome  scale  steam  engineers  have  to 
deal  with ;  it  is  very  difficult  to  remove  and  by  successive  layers 
becomes  dangerous,  on  account  of  the  thickness  to  which  it 
eventually  accumulates. 

The  carbonates  of  lime  and  magnesia  may  be  largely  arrested 
by  passing  the  feed  water  through  a  suitable  heater  and  lime 
extractor.  It  must  be  apparent  to  every  one  that  any  device 
which  will  accomplish  this  is  a  very  desirable  attachment  to  a 
steam  boiler.  As  it  is  not  possible  to  eliminate  all  the  foreign 
matter  in  the  water  from  it,  recourse  is  often  had  to  the  use  of 
solvents  and  chemical  agencies  for  the  prevention  of  scale.  Some 
of  these  are  very  simple  and  within  easy  reach ;  others  are  sur- 
rounded by  an  atmosphere  of  uncertainty  and  the  real  nature  of 
the  compound  is  hidden  under  a  meaningless  trade-mark.  For 
carbonate  of  lime,  potato  has  been  found  to  be  very  service- 
able in  preventing  the  formation  of  scale ;  its  action  appears  to 
be  that  of  surrounding  the  particles  of  lime  with  a  coating  of 
starch  and  gelatine,  and  thus  preventing  the  cohesion  of  these 
particles  to  form  a  mass.  Various  astringents  have  been  used  for 
this  purpose,  such  as  extracts  of  oak  and  hemlock  bark,  nutgalls, 
catechu,  etc.,  with  varying  success. 

Carbonate  of  soda  has  been  used  and  with  very  great  success  in 
some  localities,  not  only  in  preventing,  but  in  actually  removing 
scale  already  formed.  It  acts  on  carbonate  of  lime,  not  only,  but 
on  the  sulphate  also.  It  is  clean,  free  from  grit,  and  is  quite 
unobjectionable  in  the  boiler ;  one  or  more  pounds  per  day,  de- 
pending on  the  size  of  the  boiler,  may  be  admitted  through  the 
pump  with  the  feed  water ;  or  admitted  in  the  morning  before 


442  HANDBOOK   ON    ENGINEERING. 

firing  up,  by  simply  mixing  with  water  and  pouring  into  the  boiler 
through  the  safety  valve  or  other  opening. 

Tannate  of  soda  has  been  similarly  employed  and  is  an  excel- 
lent scale  preventive.  It  will  also  act  as  a  solvent  for  scale 
already  formed  in  the  boiler,  acting  on  sulphate  as  well  as  carbon- 
ate of  lime. 

Crude  petroleum  has  been  found  very  beneficial  in  removing 
the  hard  scale  composed  principally  of  sulphate  of  lime. 

Zinc  in  steam  boilers*  —  The  employment  of  zinc  in  steam 
boilers,  like  that  of  soda,  has  been  adopted  for  two  distinct 
objects:  (1)  to  prevent  corrosion,  and  (2)  to  prevent  and 
remove  incrustation.  To  attain  the  first  object,  it  has  been  used 
chiefly  in  marine  boilers,  and  for  the  second,  chiefly  in  boilers  fed 
with  fresh  water.  In  order  that  the  application  of  zinc  in  marine 
boilers  may  be  effective,  it  is  necessary  that  the  metallic  contact 
should  be  insured.  If  galvanic  action  alone  is  relied  upon  for  the 
protection  of  the  plates  and  tabes,  it  will  doubtless  be  diminished 
materially  by  the  coating  of  oxide  that  exists  between  all  joints  of 
plates,  whether  lapped  or  butted,  and  also  between  the  rivets  and 
the  plates.  Assuming  the  preservative  action  of  zinc  to  be  proved 
when  properly  applied,  we  have  now  two  systems  for  preventing 
the  internal  decay  of  marine  boilers,  viz. :  allowing  the  plates  and 
tubes  to  become  coated  with  scale,  and  employing  zinc.  It 
remains  to  decide  which  of  these  two  systems  is  the  best  with 
respect  to  economy  and  practicability. 

We  come  now  to  consider  the  use  of  zinc  for  preventing  arid 
removing  incrustation. 

At  one  time  it  was  considered  that  the  action  of  zinc  in  pre- 
venting incrustation  was  physical  or  mechanical.  The  particles 
of  zinc,  as  it  wasted  away,  were  supposed  to  become  mixed 
amongst  the  solid  matter  precipitated  from  the  water,  in  such  a 
manner  as  to  prevent  it  adhering  together,  so  as  to  form  a  hard 
scale  ;  or  the  particles  of  zinc  were  supposed  to  become  deposited 


HANDBOOK    ON    ENGINEERING.  443 

upon  the  plates,  and  so  prevent  the  scale  from  adhering  to  them. 
Then  it  was  suggested  that  the  zinc  acted  chemically,  and  now,  it 
is  the  generally  received  opinion  that  its  action  is  galvanic  in 
preventing  incrustation  as  well  as  in  preventing  corrosion.  When 
the  water  contains  an  excess  of  sulphates  or  chlorides  over  the 
carbonates,  the  acid  of  the  former  will  form  soluble  salts  with  the 
oxide  of  zinc,  the  surface  of  the  zinc  will  be  kept  clean,  and  the 
galvanic  current,  to  which  the  efficiency  of  the  zinc  is  due,  will  be 
maintained.  On  the  other  hand,  should  there  be  a  preponderat- 
ing amount  of  carbonates,  the  zinc  will  be  covered  first  with  oxide, 
then  with  carbonates  and  its  useful  action  arrested  and  stopped. 
It  is  quite  as  important  that  the  zinc  should  be  in  metallic  con- 
tact with  the  plates  when  used  to  prevent  incrustation,  as  when 
employed  to  prevent  corrosion.  The  application  of  zinc  for  the 
former  purpose  should  never  be  attempted  without  first  having  the 
water  analyzed  in  order  to  ascertain  whether  it  is  likely  to  be 
effective.  The  use  of  zinc  in  externally  fired  boilers  should  be 
attempted  with  great  caution,  as  when  efficacious  in  preventing 
the  formation  of  a  hard  scale,  it  is  liable  to  produce  a  heavy 
sludge  that  may  settle  over  the  furnace  plates  and  lead  to  over- 
heating. On  the  whole  we  cannot  but  regard  the  evidence  as  to 
the  effect  of  zinc  upon  incrustation  as  being  very  conflicting. 

Leaks  should  be  stopped  as  soon  as  possible  after  their  dis- 
covery ;  the  kind  of  leak  will  indicate  the  treatment  necessary. 
If  it  occurs  around  the  ends  of  the  tubes,  it  may  be  stopped  by 
expanding  the  tubes  anew ;  if  in  a  riveted  joint,  it  should  be  care- 
fully examined,  especially  along  the  line  of  the  rivets  and  care 
should  be  exercised  in  determining  whether  there  is  a  crack 
extending  from  rivet  to  rivet  along  the  line  of  the  holes ;  should 
this  prove  to  be  the  case,  the  boiler  is  then  in  an  extremely 
dangerous  condition  and  under  no  circumstances  should  it  be 
again  fired  up  until  suitable  repairs  have  been  made  which  will 
insure  its 'safety. 


444  HANDBOOK    ON    ENGINEERING. 

Blisters  occur  in  plates  which  are  made  up  of  several  thick- 
nesses of  iron  and  which  from  some  cause  were  not  thoroughly 
welded  before  the  final  rolling  into  plates.  When  such  a  plate 
comes  in  contact  with  the  heat  of  the  furnace  the  thinnest  portion 
of  the  defective  plate  4t  buckles  "  and  forms  what  is  called  a 
blister.  As  soon  as  discovered,  there  should  be  thorough  exami- 
nation of  the  plate  and  if  repairs  are  needed  there  should  be  as 
little  delay  as  possible  in  making  them.  If  the  blister  be  very 
thin  and  altogether  on  the  surface  it  may  be  chipped  and  dressed 
around  the  edges ;  if  the  thickness  is  equal  or  exceeds  Ty  the 
blister  should  be  cut  off  and  patched,  or  a  new  plate  put  in. 

Patching  boilers*  —  When  a  boiler  requires  patching  it  is  bet- 
ter to  cut  out  the  defective  sheets  and  rivet  in  a  new  one ;  or  if 
this  cannot  be  done,  a  new  piece  large  enough  to  cover  the  defect 
in  the  old  sheet  may  be  riveted  over  the  hole  from  which  the 
defective  portion  has  been  cut.  If  this  occurs  in  any  portion  of 
the  boilei  subject  to  the  action  of  fire,  the  lap  should  be  the  same 
as  the  edges  of  the  boiler  seams,  and  should  be  carefully  calked 
around  the  edges  after  the  riveting.  Whenever  the  blisters  occur 
in  a  plate,  patching  is  a  comparatively  simple  thing  as  against  the 
repairs  of  a  plate  worn  by  corrosion.  In  the  latter  case,  the 
defective  portions  of  the  plate  should  be  entirely  removed  and  the 
openings  should  show  sound  metal  all  around  and  of  full  thick- 
ness. If  this  cannot  be  obtained  within  a  reasonable  sized  open- 
ing then  the  whole  plate  should  be  removed. 

It  often  occurs  that  a  minor  defect  is  found  in  a  plate  and  at  a 
time  when  it  is  not  convenient  to  stop  for  repairs ;  in  such  an 
event  a  "  soft"  patch  is  often  applied.  This  consists  of  a  piece 
of  wrought  iron  carefully  fitted  to  that  portion  of  the  boiler  plate 
needing  repairs  ;  holes  are  fitted  in  both  plates  and  patch,  and 
"  patch  bolts  "  provided  for  them.  A  thick  putty  consisting  of 
white  and  red  lead  with  iron  borings  or  filings  in  them  placed 
evenly  over  the  inner  surface  of  the  patch,  which  is  then  tightly 


HANDBOOK    ON    ENGINEERING.  445 

bolted  to  the  boiler  plate.  This  is  best  but  a  temporary  make- 
shift and  ought  never  to  be  regarded  as  a  permanent  repair.  A 
mistake  is  often  made  of  making  a  patch  of  thicker  metal  than 
that  of  the  shell  of  the  boiler  needing  it.  A  moment's  reflection 
ought  to  show  the  absurdity  of  putting  on  a  T5F  or  f  patch  on  an 
old  J  inch  boiler  shell ;  yet  it  is  not  so  rare  as  one  would  imagine. 
A  piece  of  new  iron  T3^"  thick  will,  in  most  cases,  be  found  to  be 
stronger  than  that  portion  of  a  J"  old  plate  needing  repairs. 

Inspection*  —  A  careful  external  and  internal  examination  of  a 
boiler  is  to  be  commended  for  many  reasons.  This  should  be  as 
frequent  as  possible  and  thoroughly  done ;  it  should  include  the 
boiler  not  only,  but  all  the  attachments  which  affect  its  working 
or  pressure.  Particular  attention  should  be  paid  to  the  examina- 
tion of  all  braces  and  stays,  safety  valve,  pressure  gauges,  water 
gauges,  feed  and  blow-off  apparatus,  etc. ;  these  latter  refer  more 
particularly  to  constructive  details  necessary  to  proper  manage- 
ment and  safety.  The  inspection  would  obviously  be  incomplete, 
did  it  not  include  an  examination  into  the  causes  of  "  wear  and 
tear,"  and  determine  the  extent  to  which  it  had  progressed. 
Among  the  several  causes  which  directly  tend  to  rendering  a 
boiler  unsafe,  may  be  mentioned  the  dangerous  results  occasioned 
by  the  overheating  of  plates,  thus  changing  the  structure  of  the 
iron  from  fine  granular,  or  fibrous,  to  coarse  crystalline.  This 
may  easily  be  detected  by  examination,  and  will  in  general  be 
found  to  occur  in  such  cases  where  the  boilers  are  too  small  for 
the  work,  are  fired  too  hard,  or  have  a  considerable  accumulation 
of  scale  or  sediment  in  contact  with  the  plates.  Blistered  plates 
are  almost  instantly  detected  at  sight,  so  also  is  corrosion,  from 
whatever  cause  it  may  have  proceeded. 

Corrosion  of  boiler  plates*  —  Iron  will  corrode  rapidly  when 
subjected  to  the  intermittent  action  of  moisture  and  dryness. 
Land  boilers  are  less  subject  to  corrosion  than  marine  boilers. 
The  corrosion  of  a  boiler  may  be  either  external  or  internal.  Ex- 


446  HANDBOOK    ON    ENGINEERING. 

ternal  corrosion  may,  in  general,  be  easily  prevented  by  carefully 
caulking  all  leaks  in  the  boiler ;  by  preventing  the  dropping  of 
water  on  the  plates,  such,  for  example,  as  from  a  leaky  joint  in 
the  steam  pipe  or  from  the  safety  valve.  A  leaky  roof,  by  allow- 
ing a  continual  or  occasional  dropping  of  water  on  the  top  of  a 
boiler,  especially  if  the  boiler  is  not  in  constant  use,  would  pro- 
mote external  corrosion.  Sometimes  external  corrosion  is  caused 
by  the  use  of  coal  having  sulphur  in  it,  and  acts  in  this  way :  The 
sulphur  passes  off  from  the  fire  as  sulphurous  oxide,  which  often 
attaches  to  the  sides  of  a  boiler ;  so  long  as  this  is  dry  no  especial 
mischief  is  done ;  but  if  it  comes  in  contact  with  a  wet  plate  the 
sulphurous  oxide  is  converted  into  sulphuric  acid  over  so  much 
of  the  surface  as  the  moisture  extends ;  this  acid  attacks,  and 
will,  in  time,  entirely  destroy  the  boiler  plate.  Internal  corrosion 
is  not  so  easily  accounted  for  and  is  very  difficult  to  correct, 
especially  when  it  occurs  above  the  water  line.  It  is  generally 
believed  to  be  due  to  the  action  of  acids  in  the  feed  water. 
Marine  boilers  are  especially  subject  to  internal  corrosion  when 
used  in  connection  with  surface  condensers.  A  few  years  ago  it 
was  generally  supposed  to  be  due  to  galvanic  action  but  that  idea 
is  now  almost  entirely  given  up.  From  the  fact  that  boilers  using 
distilled  water  fed  into  them  from  surface  condensers  are  more 
liable  to  internal  corrosion  than  other  boilers,  has  led  to  the  theory 
that  it  is  the  pure  water  that  does  the  mischief,  and  that  a  water 
containing  in  slight  degree  a  scale-forming  salt,  is  to  be  preferred 
to  water  which  is  absolutely  pure.  Whatever  maybe  the  truth  or 
falsity  of  this  theory,  it  is  a  well  established  fact  that  distilled 
water  has  a  most  pernicious  action  on  various  metals,  especially 
on  steel,  lead  and  iron.  This  action  is  attributed  to  its  peculiar 
property,  as  compared  with  ordinary  water,  of  dissolving  free 
carbonic  acid.  One  of  the  worst  features  in  connection  with 
internal  corrosion  is  that  its  progress  cannot  be  easily  traced  on 
account  of  the  boiler  being  closed  while  at  work.  As  it  does  not 


HANDBOOK    ON    ENGINEERING.  447 

usually  extend  over  any  very  great  extent  of  surface,  the  ordinary 
hydraulic  test  fails  to  reveal  the  locality  of  corroded  spots  ;  the 
hammer  test,  on  the  contrary,  rarely  fails  to  locate  them,  if  the 
plates  are  much  thinned  by  its  action. 

Testing  boilers* — It  is  the  general  practice  to  apply  the 
hydraulic  test  to  all  new  steam  boilers  at  the  place  of  manufacture, 
and  before  shipment.  The  pressure  employed  in  the  test  is  from 
one  and  a  half  to  twice  the  intended  working  steam  pressure. 
This  test  is  only  valuable  in  bringing  to  notice  defects  which 
would  escape  ordinary  inspection.  It  is  not  to  be  assumed  that 
it  in  any  way  assures  good  workmanship,  or  material,  or  good 
design,  or  proper  proportions ;  it  simply  shows  that  the  boiler 
being  tested  is  able  to  withstand  this  pressure  without  leak- 
ing at  the  joints,  or  distorting  the  shell  to  an  injurious  degree. 
Bad  workmanship  may  often  be  detected  at  a  glance  by  an  expe- 
rienced person.  The  material  must  be  judged  by  the  tensile 
strength  and  ductility  of  the  sample  tested.  The  design  and  pro- 
portions are  to  be  judged  on  constructive  grounds,  and  have  little 
or  nothing  in  common  with  the  hydraulic  test.  The  great  majority 
of  buyers  of  steam  boilers  have  but  little  knowledge  on  the  sub- 
ject of  tests,  and  too  often  conclude  that  if  they  have  a  certified 
copy  of  a  record  showing  that  a  particular  boiler  withstood  a  test 
of  say,  150  Ibs.,  it  is  a  good  and  safe  boiler  at  75  to  100  Ibs. 
steam  pressure.  If  the  boiler  is  a  new  one  and  by  a  reputable 
maker,  that  may  be  true ;  if  it  has  been  used  and  put  upon  the 
market  as  a  second-hand  boiler,  it  may  be  anything  but  safe  at 
half  the  pressure  named.  By  the  hydraulic  test,  the  braces  in  a 
boiler  may  be  broken,  joints  strained  so  as  to  make  them  leak, 
bolts  or  pins  may  be  sheared  off,  or  so  distorted  as  to  be  of  little 
or  no  service  in  resisting  steam  when  pressure  is  on. 

Hammer  test*  —  The  practice  of  inspecting  boilers  by  sounding 
with  a  hammer  is,  in  many  respects,  to  be  commended.  It 
requires  some  practical  experience  in  order  to  detect  blisters  and 


448 


HANDBOOK    ON    ENGINEERING. 


tlie  wasting  of  plates,  by  sound  alone.  The  hammer  test  is 
especially  applicable  to  the  thorough  inspection  of  old  boilers.  It 
frequently  happens  in  making  a  test  that  a  blow  of  the  hand 
hammer  will  either  distort  it,  or  be  driven  entirely  through  the 
plate ;  and  it  is  just  here  that  the  superiority  of  this  method  of 
testing  over,  or  in  connection  with  the  hydraulic  test,  becomes 
fully  apparent.  The  location  of  stays,  joints  and  boiler  fittings  all 
modify  and  are  apt  to  mislead  the  inspector  if  he  depends  upon 
sound  alone.  There  is  a  certain  spring  of  the  hammer  and  a  clear 
ring  indicative  of  sound  plates,  which  are  wanting  in  plates  much 
corroded  or  blistered.  The  presence  of  scale  on  the  inside  of  the 
boiler  has  a  modifying  action  on  the  sound  of  the  plate.  When  a 
supposed  defect  is  discovered,  a  hole  should  be  drilled  through 
the  sheet  by  which  its  thickness  may  be  determined,  as  well  as 
its  condition. 

In  order  to  thoroughly  inspect  a  boiler,  the  inspector  should 
crawl  into  the  boiler  (when  it  is  possible  to  do  so)  and  he  should 
look  for  pitting  and  grooving  of  plates,  test  all  braces,  and 
examine  all  inlets  and  outlets. 

TOTAL  STORED  ENERGY  OP  STEAM  BOILERS. 


Grate 
Surface. 

Heating 
Surface. 

Steam 
Pressure. 

Rated 

Energy  in  Foot  Pounds  Stored  in  the 

feq.  Ft. 

Sq.  Ft. 

Lbd. 

H.  P. 

Water. 

Steam. 

Total. 

15 

120 

100 

10 

46605200 

676698 

47281898 

15 

875 

125 

425 

64253160 

1302431 

65556691 

20 

400 

150 

35 

80572050 

2377357 

8294  9407 

20 

1200 

125 

600 

64452270 

1766447 

66218718 

22 

1070 

125 

525 

52561075 

1483896 

54044971 

30 

852 

75 

60 

60008790              1022731 

51031521 

30 

1350 

125 

650 

69148790               21358U2 

71284692 

32 

768 

75 

300 

71272370               1462430 

72734800 

36 

730 

30 

60 

57570750 

709310 

58260060 

50 

1119 

75 

350 

107408340               2316392 

109724732 

70 

2806 

100 

250 

172455270 

2108110 

1745633feO 

72 

1755 

30 

180 

102628410 

1643854 

104272264 

72 

2324 

bO 

200 

90531490 

1570517 

92101987 

100 

3000 

100 

250 

227366000 

3513830 

230879830 

HANDBOOK   ON   ENGINEERING.  449 


CHAPTER     XVII. 
USE  AND  ABUSE  OF  THE  STEAM-BOILER. 

Steam-boilers*  —  A  steam-boiler  may  be  defined  as  a  close 
vessel,  in  which  steam  is  generated.  It  may  assume  an  endless 
variety  of  forms,  and  can  be  constructed  of  various  materials. 
Since  the  introduction  of  steam  as  a  motive  power  a  great  variety 
of  boilers  have  been  designed,  tried  and  abandoned;  while  many 
others,  having  little  or  no  merit  as  steam  generators,  also  have 
their  advocates  and  are  still  continued  in  use.  Under  such  cir- 
cumstances, it  is  not  surprising  that  quite  a  variety  of  opinions 
are  held  on  the  subject.  This  difference  of  opinion  relates  not 
only  to  the  form  of  boiler  best  adapted  to  supply  the  greatest 
quantity  of  steam  with  the  least  expenditure  of  fuel,  but  also  to 
the  dimensions  or  capacity  suitable  for  an  engine  of  a  given  num- 
ber of  horse-power ;  and  while  great  improvements  have  been 
made  in  the  manufacture  of  boiler  materials  within  the  past 
fifteen  years,  yet  the  number  of  inferior  steam-boilers  seem  to 
increase  rather  than  diminish.  It  would  be  difficult  to  assign  any 
reasonable  cause  for  this,  except  that,  of  late  years,  nearly  the 
whole  attention  of  instructors  and  mechanical  engineers  has  been 
directed  to  the  improvement  and  perfection  of  the  steam-engine, 
and  practical  engineers,  following  the  example  set  by  the  leaders, 
devote  their  energies  to  the  same  object.  This  is  to  be  regretted, 
as  the  construction  and  application  of  the  steam-boiler,  like  the 
steam-engine,  is  deserving  of  the  most  thorough  and  scien- 
tific study,  as  on  the  basis  of  its  employment  rest  some 
of  the  most  important  interests  of  civilization.  Until  quite 
recently,  the  idea  was  very  generally  entertained  that  the 
purely  mechanical  skill  required  to  enable  a  person  to  join 


450  HANDBOOK    ON    ENGINEERING. 

- 

together  pieces  of  metal,  and  thereby  form  a  steam-tight  and 
water-tight  vessel  of  given  dimensions,  to  be  used  for  the  gen- 
eration of  steam  to  work  an  engine,  was  all  that  was  needed  ; 
experience  has  shown,  however,  that  this  is  but  a  small  portion  of 
the  knowledge  that  should  be  possessed  by  persons  who  turn  their 
attention  to  the  design  and  construction  of  steam-boilers,  as  the 
knowledge  wanted  for  this  end  is  of  a  scientific  as  well  as  of  a 
mechanical  nature.  As  the  boiler  is  the  source  of  power  and  the 
place  where  the  power  to  be  applied  is  first  generated,  and  alsc 
the  source  from  which  the  most  dangerous  consequences  may  arise 
from  neglect  or  ignorance,  it  should  attract  the  special  attention 
of  the  designing  and  mechanical  engineer,  as  it  is  well  known 
that  from  the  hour  it  is  set  to  work,  it  is  acted  upon  by  destroy- 
ing forces,  more  or  less  uncontrollable  in  their  work  of  destruc- 
tion. These  forces  may  be  distinguished  as  chemical  and 
mechanical.  In  most  cases  they  operate  independently,  though 
they  are  frequently  found  acting  conjointly  in  bringing  about  the 
destruction  of  the  boiler,  which  will  be  more  or  less  rapid  accord- 
ing to  circumstances  of  design,  construction,  quality  of  material, 
management,  etc.  The  causes  which  most  affect  the  integrity  of 
boilers  and  limit  their  usefulness  are  either  inherent  in  the  mate- 
rial, or  due  to  a  want  of  skill  in  their  construction  and  manage- 
ment ;  they  may  be  enumerated  as  follows :  — 

First,  inferior  material ;  second,  slag,  sand  or  cinders  being 
rolled  into  the  iron ;  third,  want  of  lamination  in  the  sheets ; 
fourth,  the  overstretching  of  the  fiber  of  the  plate  on  one  side  and 
puckering  on  the  other  in  the  process  of  rolling,  to  form  the  circle 
for  the  shell  of  a  boiler ;  fifth,  injuries  done  the  plate  in  the  pro- 
cess of  punching ;  sixth,  damage  induced  by  the  use  of  the  drift- 
pin  ;  seventh,  carelessness  in  rolling  the  sheets  to  form  the  shell, 
as  a  result  of  which  the  seams,  instead  of  fitting  each  other 
exactly,  have  in  many  instances  to  be  drawn  together  by  bolts, 
which  aggravates  the  evils  of  expansion  and  contraction  when  the 


HANDBOOK    ON    ENGINEERING.  451 

boiler  is  in  use ;  eighth,  injury  done  the  plates  by  a  want  of  skill 
in  the  use  of  the  hammer  in  the  process  of  hand-riveting ;  ninth, 
damage  done  in  the  process  of  calking. 

Other  causes  of  deterioration  are  unequal  expansion  and  con- 
traction, resulting  from  a  want  of  skill  in  setting  ;  grooving  in  the 
vicinity  of  the  seams ;  internal  and  external  corrosion ;  blowing 
out  the  boiler  when  under  a  high  pressure  and  filling  it  again  with 
cold  water  when  hot ;  allowing  the  fire  to  burn  too  rapidly  after 
starting,  when  the  boiler  is  cold  ;  ignorance  of  the  use  of  the  pick 
in  the  process  of  scaling  and  cleaning ;  incapacity  of  the  safety- 
valve  ;  excessive  firing ;  urging  or  taxing  the  boiler  beyond  its 
safe  and  easy  working  capacity;  allowing  the  water  to  become 
low,  and  thus  causing  undue  expansion  ;  deposits  of  scale  accum- 
ulating on  the  parts  exposed  to  the  direct  action  of  the  fire, 
thereby  burning  or  crystallizing  the  sheets  or  shell ;  wasting  of  the 
material  by  leakage  and  corrosion ;  bad  design  and  construction 
of  the  different  parts  ;  inferior  workmanship  and  ignorance  in  the 
care  and  management.  All  these  tend  with  unerring  certainty  to 
limit  the  age  and  safety  of  steam  boilers.  On  account  of  want  of 
skill  on  the  part  of  the  designer  and  avarice  on  the  part  of  the 
manufacturer,  or  perhaps  both  reasons,  boilers  are  sometimes  so 
constructed  as  to  bring  a  riveted  seam  directly  over  the  fire,  the 
result  of  which  is  that  in  consequence  of  one  lap  covering  the 
other,  the  water  is  prevented  from  getting  to  the  one  nearest  the 
fire,  for  which  reason  the  lap  nearest  the  fire  becomes  hotter  and 
expands  to  a  much  greater  extent  than  any  other  part  of  the 
plate ;  and  its  constant  unequal  expansion  and  contraction,  as 
the  boiler  becomes  alternately  hot  and  cold,  inevitably  results  in  a 
crack.  Such  blunders  are  aggravated  by  the  scale  and  sediment 
being  retained  on  the  inside,  between  the  heads  of  the  rivets, 
which  should  be  properly  removed  in  cleaning. 

The  tendency  of  manufacturers  to  work  boilers  beyond  their 
capacity,  especially  when  business  is  driving,  is  too  great  in  this 


452  HANDBOOK    ON    ENGINEERING. 

country  ;  and  no  doubt  many  boiler  explosions  may  be  attributed 
to  this  cause.  Boilers  are  bought,  adapted  to  the  wants  of  the 
manufactory  at  the  time,  but,  as  business  increases,  machinery 
is  added  to  supply  the  demand  for  goods,  until  the  engine  is 
overtasked,  the  boiler  strained  and  rendered  positively  danger- 
ous. Then  again,  it  not  unfrequently  occurs  that  engines  in 
manufactories  are  taken  out  and  replaced  by  those  of  increased 
power,  while  the  boilers  used  with  the  old  engine  are  retained  in 
place,  with  more  or  less  cleaning  and  patching,  as  the  case  may 
require.  Now,  it  is  evident  to  any  practical  mind  that  boilers 
constructed  for  a  twenty  horse  power  engine  are  ill  adapted  to 
an  engine  of  forty  horse  power,  more  especially  if  those  boilers 
have  been  used  for  a  number  of  years.  In  order  to  supply 
sufficient  steam  for  the  new  engine,  with  a  cylinder  of  increased 
capacity,  the  boiler  must  be  worked  beyond  its  safe  working 
pressure,  consequently  excessive  heating  and  pressure  greatly 
weaken  it  and  endanger  the  lives  of  those  employed  in  the  vicinity. 
The  danger  and  impracticability  of  using  boilers  with  too 
limited  steam  room  may  be  explained  thus :  Suppose  the  entire 
steam  room  in  a  boiler  to  be  six  cubic  feet,  and  the  contents  of 
the  cylinder  which  it  supplies  to  be  two  cubic  feet ;  then  at  each 
stroke  of  the  piston  one-third  of  all  the  steam  in  the  boilers  is 
discharged,  and  consequently,  one-third  of  the  pressure  on  the 
surface  of  the  water  before  that  stroke  is  relieved ;  hence,  it  will 
be  seen  that  excessive  fires  must  be  kept  up  in  order  to  generate 
steam  of  sufficiently  high  temperature  and  pressure  to  supply  the 
demand.  The  result  is  that  the  boilers  are  strained  and  burned. 
Such  economy  in  boiler  power  is  exceedingly  expensive  in  fuel, 
to  say  nothing  of  the  danger.  Excessive  firing  distorts  the  fire- 
sheets,  causing  leakage,  undue  and  unequal  expansion  and  con- 
traction, fractures,  and  the  consequent  evils  arising  from  external 
corrosion.  Excessive  pressure  arises  generally  from  a  desire  on 
the  part  of  the  steam-user  to  make  a  boiler  do  double  the  work  for 


HANDBOOK    ON    ENGINEERING.  453 

which  it  was  originally  intended.  A  boiler  that  is  constructed  to 
work  safely  at  from  fifty  to  sixty  pounds  was  never  intended  to 
run  at  eighty  and  ninety  pounds  ;  more  especially  if  it  had  been 
in  use  for  several  years.  Boilers  deteriorated  by  age  should  have 
their  pressure  decreased,  rather  than  increased. 

One  of  the  first  things  that  should  be  done  in  manufacturing 
establishments  would  be  to  provide  sufficient  boiler  power  and,  in 
order  to  do  this,  the  work  to  be  done  ought  to  be  accurately  cal- 
culated and  the  engine  and  boilers  adapted  to  the  results  of  this 
calculation.  Steam  users  themselves  are  frequently  to  blame  for 
the  annoyances  and  dangers  arising  from  unsafe  boilers  and  those 
of  insufficient  capacity.  From  motives  of  false  economy  they  are 
too  easily  swayed  in  favor  of  the  cheaper  article,  simply  because 
it  is  cheap,  when  they  should  consider  they  are  purchasing  an 
article  which,  of  almost  all  others,  should  be  made  in  the  most 
thorough  manner  and  of  the  best  material.  In  view  of  the  fearful 
explosions  that  occur  from  time  to  time,  every  steam  user  should 
secure  for  his  use  the  best  and  safest.  The  object  of  a  few 
dollars  as  between  the  work  of  a  good,  responsible  maker  and 
that  of  an  irresponsible  one,  should  not  for  one  moment  be 
entertained. 

It  is  very  bad  policy  for  steam-users  to  advertise  for  estimates 
for  steam-boilers,  or  to  inform  all  the  boilermakers  in  the  town 
or  city  that  a  boiler  or  boilers  to  supply  steam  for  an  engine  of  a 
certain  size  is  needed,  because  in  this  way  steam-users  frequently 
find  themselves  in  the  hands  of  needy  persons,  who,  in  their 
anxiety  to  get  an  order,  will  sometimes  ask  less  for  a  boiler  than 
they  can  actually  make  it  for ;  consequently,  they  have  to  cheat 
in  the  material,  in  the  workmanship,  in  the  heating  surface  and  in 
the  fittings.  As  a  result,  the  boiler  is  not  only  a  continual  source 
of  annoyance,  but,  in  many  instances,  an  actual  source  of  danger. 
The  most  prudent  course,  and  in  fact  the  only  one  that  may  be 
expected  to  give  satisfaction,  is  to  contract  with  some  responsible 


434  HANDBOOK    ON    ENGINEERING. 

manufacturer  that  has  an  established  reputation  for  honesty, 
capability  and  fair  dealing,  and  who  will  not  allow  himself  to  be 
brought  in  competition  with  irresponsible  parties  for  the  purpose 
of  selling  a  boiler.  There  are  thousands  of  boilers  designed,  con- 
structed and  set  up  in  such  a  manner  as  to  render  it  utterly 
impossible  to  examine,  clean  or  repair  them.  Generally,  in  such 
cases,  in  consequence  of  imperfect  circulation,  the  water  is 
expelled  from  the  surface  of  the  iron  at  the  points  where  the 
extreme  heat  from  the  furnace  impinges,  and,  as  a  result,  the 
plates  become  overheated  and  bulge  outward,  which  aggravates 
the  evil,  as  the  hollow  formed  by  the  bulge  becomes  a  receptacle 
for  scale  and  sediment.  By  continued  overheating,  the  parts 
become  crystallized  and  either  crack  or  blister ;  this,  if  not 
attended  to  and  remedied,  will  eventually  end  in  the  destruction 
of  the  boiler.  Many  boilers,  to  all  appearance  well  made  and  of 
good  material,  give  considerable  trouble  by  leakage  and  fracture, 
owing  to  the  severe  strains  of  unequal  expansion  and  contraction 
induced  by  the  rigid  construction,  the  result  of  a  want  of  skill  in 

the  original  design. 

• 

DESIGN  OF  STEAM-BOILERS. 

It  has  become  a  general  assertion  on  the  part  of  writers  on  the 
steam-boiler  that  the  most  important  object  to  be  attained  in  its 
design  and  arrangement  is  thorough  combustion  of  the  fuel. 
This  is  only  partially  true  as  there  are  other  conditions  equally 
important,  among  which  are  strength,  durability,  safety,  economy 
and  adaptability  to  the  particular  circumstances  under  which  it  is 
to  be  used.  However  complete  the  combustion  may  be,  unless 
its  products  can  be  easily  and  rapidly  transferred  to  the  water, 
and  unless  the  means  of  escape  of  the  steam  from  the  surfaces  on 
which  it  is  generated  is  easy  and  direct,  the  boiler  will  fail  to 
produce  satisfactory  results,  either  in  point  of  durability  or 
economy  of  fuel. 


HANDBOOK    ON    ENGINEERING.  455 

Strength  means  the  power  to  sustain  the  internal  pressure  to 
which  the  boiler  may  be  subjected  in  ordinary  use,  and  under 
careful  and  intelligent  management.  To  secure  durability,  the 
material  must  be  capable  of  resisting  the  chemical  action  of  the 
minerals  contained  in  the  water,  and  the  boiler  ought  to  be 
designed  so  as  to  procure  the  least  strain  under  the  highest  state 
of  expansion  to  which  it  may  be  subjected  —  be  so  constructed 
that  all  the  parts  will  be  subjected  to  an  equal  expansion,  con- 
traction, push,  pull  and  strain,  and  be  intelligently  and  thoroughly 
cared  for  after  being  put  in  use.  These  objects,  however,  can 
only  be  obtained  by  the  aid  of  a  knowledge  of  the  principles  of 
mechanics,  the  strength  and  resistance  of  materials,  the  laws  of 
expansion  and  contraction,  the  action  of  heat  on  bodies,  etc. 
The  economy  of  a  steam  boiler  is  influenced  by  the  following  con- 
ditions: cost  and  quantity  of  the  material,  design,  character  of  the 
workmanship  employed  in  its  construction,  space  occupied,  capa- 
bility of  the  material  to  resist  the  chemical  action  of  the  ingredi- 
ents contained  in  the  water,  the  facilities  it  affords  for  the 
transmission  of  the  heat  from  the  furnace  to  the  water,  etc.  The 
safety  of  any  structure  depends  on  the  designer's  knowledge  of 
the  principles  of  mechanics,  the  resistance  of  materials  and  the 
action  of  bodies  as  influenced  by  the  elements  to  which  they  are 
exposed ;  and -in  the  case  of  steam  boilers,  the  safety  depends  on 
the  judgment  of  the  designer,  the  quality  of  the  material,  the 
character  of  the  workmanship  and  the  skill  employed  in  the  man- 
agement. Safety  is  said  to  be  incompatible  with  economy,  but 
this  is  undoubtedly  a  mistake,  as  an  intelligent  economy  includes 
permanence  and  seeks  durability.  Adaptability  to  the  peculiar 
purposes  for  which  they  are  to  be  used  is  one  of  the  first  objects 
to  be  sought  for  in  the  design  and  construction  of  any  class  of 
machines,  vessels  or  instruments,  and  it  is  undoubtedly  this  that 
gave  rise  to  the  great  variety  of  designs,  forms  and  modifications 
of  steam  boilers  in  use  at  the  present  day,  which  are,  with  very 


456  HANDBOOK    ON    ENGINEERING. 

few  exceptions,  the  result  of  thought,   study,  investigation  and 
experiment. 

FORMS  OF  STEAfl-BOILERS. 

According  to  the  well-known  law  of  hydrostatics,  the  pressure 
of  steam  in  a  close  cylindrical  vessel  is  exerted  equally  in  all 
directions.  In  acting  against  the  circumference  of  a  cylinder, 
the  pressure  must,  therefore,  be  regarded  as  radiating  from  the 
axis,  and  exerting  a  uniform  tensional  strain  throughout  the 
inclosing  material. 

Familiarity  with  steam  machinery,  more  especially  with  boil- 
ers, is  apt  to  beget  a  confidence  in  the  ignorant  which  is  not 
founded  on  a  knowledge  of  the  dangers  by  which  they  are  contin- 
ually surrounded ;  while  contact  with  steam,  and  a  thoroughly 
elementary  knowledge  of  its  constituents,  theory  and  action,  only 
incline  the  intelligent  engineer  and  fireman  to  be  more  cautious 
and  energetic  in  the  discharge  of  their  duties.  Many  regard 
steam  as  an  incomprehensible  mystery ;  and  although  they  may 
employ  it  as  a  power  to  accomplish  work,  know  little  of  its 
character  or  capabilities.  Steam  may  be  managed  by  common 
sense  rules  as  well  as  any  other  power ;  but  if  the  laws  which 
regulate  its  use  are  violated,  it  reports  itself,  and  often  in  louder 
tones  than  is  pleasant.  If  steam-boilers  in  general  were  better 
cared  for  than  they  are,  their  working  age  might  be  greatly  in- 
creased. Deposits  of  incrustation,  small  leaks  and  slight  cor- 
rosion, are  too  often  neglected  as  matters  of  little  consequence, 
but  they  are  the  forerunners  of  expensive  repairs,  delay  and 
disaster. 

SETTING   STEAM-BOILERS. 

While  engineers  differ  very  much  in  opinion  respecting  the  best 
manner  of  setting  boilers,  they  all  readily  allow  that  the  results 
obtained,  as  regards  economy  of  fuel  and  the  generation  of  steam, 


HANDBOOK    QN    ENGINEERING.  457 

depend  in  a  great  measure  on  the  arrangement  of  the  setting. 
Particularly  is  this  the  case  with  horizontal  tubular  boilers,  and 
there  have  been  numerous  plans  introduced  to  obtain  a  maximum 
of  steam  with  a  minimum  of  fuel.  Some  of  the  most  practical 
designs  and  best  laid  plans  are  frequently  rendered  useless  for 
want  of  knowledge  on  the  part  of  those  whose  duty  it  is  to  exe- 
cute or  carry  them  out.  This  has  perhaps  been  more  frequently 
the  case  as  regards  the  setting  of  steam  boilers  than  any  other 
class  of  machines,  as  it  is  customary  for  owners  of  steam  boilers 
to  depend  too  much  on  the  knowledge  of  masons  and  bricklayers ; 
consequently,  a  great  many  blunders  have  been  made  which 
necessitated  changes  in  the  size  of  gratebars,  alteration  of  brick- 
work, alteration  of  flues,  chimney,  etc.,  with  a  list  of  other  annoy- 
ances, such  as  insufficiency  of  steam,  poor  draught,  or  something 
else.  In  setting  or  putting  in  boilers,  all  the  surface  possible  should 
be  exposed  to  the  action  of  the  heat  of  the  fire,  not  only  that  the 
heat  may  be  thus  completely  absorbed,  but  that  a  more  equal  ex- 
pansion and  contraction  of  the  structure  may  be  obtained.  Long 
boilers  are  often  hung  by  means  of  loops  riveted  to  the  top  of 
them  and  connected  to  crossbeams  and  arches  resting  on  masonry 
above  them,  by  means  of  hangers.  This  is  a  very  .mischievous 
arrangement,  unless  turn-buckles,  or  some  other  contrivance,  are 
used  to  maintain  a  regular  strain  on  all  the  hangers,  as  long  boil- 
ers exposed  to  excessive  heat  are  apt  to  lengthen  on  the  lower 
side  and  relieve  the  end  hangers  of  any  weight;  consequently, 
the  whole  strain  is  transmitted  to  the  central  hanger,  which  has  a 
tendency  to  draw  the  boiler  out  of  shape  —  in  many  instances 
inducing  excessive  leakage,  rupture,  and,  eventually,  explosion. 

DEFECTS   IN  THE  CONSTRUCTION  OF   STEAM-BOILERS. 

The  following  cuts  illustrate  some  of  the  mechanical  defects 
that  impair  the  strength  and  limit  the  safety  and  durability  of 


458 


HANDBOOK    ON    ENGINEERING. 


steam  boilers.  All  punched  holes  are  conical,  and  unless  the 
sheets  are  reversed  after  being  punched,  so  as  to  bring  the 
small  sides  of  the  holes  together,  it  will  be  impossible  to  fill  them 
with  the  rivets.  Fig.  251  shows  the  position  of  the  rivet  in  the 
hole  without  the  sheets  being  reversed  ;  and  it  will  be  observed 
that,  as  very  little  of  the  rivet  bears  against  the  material,  the  ex- 
pansion and  contraction  of  the  boiler  have  a  tendency  to  work  it 
loose.  It  is  apparent  that  such  a  seam  would  not  possess  over 
one-third  the  strength  that  it  would  if  the  holes  in  the  sheets 


Fig.  251. 


Fig.  252. 


258. 


Fig.  254. 


Fig.  255. 


Fig.  256. 


Showing  positions  of  rivet  in  rivet  hole. 

were  reversed  and  thoroughly  filled  with  the  rivet,  as  shown  in 
Fig.  252.  Fig.  253  represents  what  is  known  in  boilermaking 
as  a  blind  hole,  which  means  that  the  holes  do  not  come  opposite 
each  other  when  the  seams  are  placed  together  for  the  purpose  of 
riveting.  Fig.  254  shows  the  position  of  the  rivet  in  the  blind  hole 
after  being  driven.  It  will  be  observed  that  the  heads  of  the 
rivet,  in  consequence  of  its  oblique  position  in  the  hole,  bear  only 
on  one  side,  and  that  even  the  bearing  is  very  limited,  and 
through  the  expansion  and  contraction  of  the  boiler,  is  liable  to 


HANDBOOK    ON    ENGINEERING.  459 

work  loose  and  become  leaky.  Such  a  seam  would  be  actually 
weaker  than  that  presented  in  Fig.  251.  Fig.  255  shows  the 
metal  distressed  and  puckered  on  each  side  of  the  blind  hole  in  the 
sheets,  which  is  the  result  of  efforts  on  the  part  of  the  boiler- 
maker,  by  the  use  of  the  drift-pin,  to  make  the  holes  correspond 
for  the  purpose  of  inserting  the  rivet.  Fig.  256  shows  the  metal 
broken  through  by  the  same  means.  Now,  it  will  be  observed 
that  nearly  all  the  above  defects  are  the  result  of  ignorance  and 
carelessness,  showing  a  want  of  skill  in  laying  out  the  work,  as 
well  as  a  want  of  proper  appliances  for  that  purpose.  The  evils 
arising  from  such  defects  are  greatly  aggravated  by  the  fact  that 
they  are  all  concealed,  frequently  defying  the  closest  scrutiny,  and 
are  only  revealed  by  those  forces  which  unceasingly  act  on  boilers 
when  in  use.  Such  pernicious  mechanical  blunders  ought  to  be 
condemned,  as  they  are  always  the  forerunners  of  destruction 
and  death.  There  can  be  no  reason  why  boilers  should  not  be 
constructed  with  the  same  degree  of 'accuracy,  judgment  and  skill 
as  is  considered  so  essential  for  all  other  classes  of  machinery. 

IMPROVEMENTS  IN   STEAM  BOILERS. 

Until  quite  recently  the  steam  boiler  has  undergone  very  little 
improvement.  This  arose,  perhaps,  from  the  fact  that  men  of 
intelligence  and  mechanical  genius  directed  their  thoughts  and 
labors  to  something  more  inviting  and  less  laborious  than  the 
construction  of  steam  boilers.  Consequently,  that  branch  of 
mechanics  was  left  almost  entirely  to  a  class  of  men  that  had  not 
the  genius  to  rise  in  their  profession  or  improve  much  in  anything 
they  attempted.  As  a  result  ignorance,  stupidity  and  a  kind  of 
brute  force  were  the  predominant  requirements  in  the  construc- 
tion of  the  steam  boiler  ;  but  within  the  past  few  years  this  state 
of  things  has  been  changed,  as  some  very  important  improvements 
have  been  made,  not  only  in  the  manufacture  of  the  material  of 
which  boilers  are  made,  but  also  in  the  mode  of  constructing 


460  HANDBOOK    ON    ENGINEERING. 

them.  The  imposing,  powerful  and  accurate- boiler  machinery  in 
use  at  the  present  time  is  an  evidence  that  the  attention  of  emi- 
nent mechanics  and  manufacturers  is  directed  to  the  steam  boiler, 
and  that  in  the  future  its  improvement  will  keep  pace  with  that  of 
the  steam  engine. 

Boiler  plate  is  now  rolled  of  sufficient  dimensions  to  form  the 
rings  for  boilers  of  any  diameter  with  only  one  seam,  obviating 
the  necessity  of  bringing  riveted  seams  in  contact  with  the  fire; 
as  was  usually  the  case  in  former  times.  In  the  manner  of  laying 
off  the  holes  for  the  rivets,  accurate  steel  gauges  have  taken  the 
place  of  the  old-fashioned  wooden  templet,  thereby  removing  the 
evils  induced  by  blind  holes,  and  obviating  the  necessity  of  using 
the  drift-pin.  So,  also,  in  the  method  of  bending  the  sheets  to 
form  the  requisite  circle  —  with  a  better  class  of  machinery,  the 
work  is  now  mo  re  accurately  performed.  The  old  process  of  chip- 
ping is,  in  nearly  all  the  large  boilershops,  superseded  by  planing 
the  bevels  on  the  edge  of  the  sheet,  preparatory  to  calking.  Recent 
improvements  in  u  calking  "  have  resulted  in  perfect  immunity  from 
the  injuries  formerly  inflicted  on  boilers  in  that  process. 
In  most  establishments  of  any  repute  in  this  country,  riveting  is 
done  by  machinery,  which  is  (as  is  well  known  to  all  intelligent 
mechanics)  very  much  superior  to  hand  riveting.  It  is  only 
small  shops  that  enter  into  rivalry  to  secure  orders  and  build 
cheap  boilers,  using  poor  material  and  an  inferior  quality  of 
mechanical  skill,  that  use  the  same  old  crude  appliances  —  in 
many  cases  the  merest  makeshifts  —  that  were  in  use  a  quarter  of 
a  century  ago,  and  constructed  without  regard  to  any  of  the  rules 
of  design  that  are  considered  so  essential  in  appliances  for  the 
construction  of  all  other  classes  of  machinery.  Every  engineer 
should  inform  himself  on  the  subject  of  the  safe  working  pressure 
of  boilers,  and  when  he  finds  the  limit  of  safety  has  been  reached, 
he  should  promptly  inform  his  employer  and  use  his  influence  to 
have  the  boiler  worked  within  the  bounds  of  safety. 


HANDBOOK   ON   ENGINEERING.  461 

To  find  the  heating  surface  of  a  water  tube  boiler :  — 

Rule*  —  Add  the  combined  outside  area  of  the  tubes  in  square 
feet  to  one-half  the  area  of  the  shell  of  the  steam  drum  in  square 
feet  and  the  sum  will  give  the  total  heating  surf  ace  0 

Example  f* —  What  is  the  heating  surface  of  a  water  tube 
boiler  having  fifty  tubes,  each  three  inches  outside  diameter  and 
fifteen  feet  long,  and  the  steam  drum  thirty-two  inches  in 
diameter  and  fifteen  feet  long  ? 

Operation*  —  3  X  3.1416  equals  9.4248  inches,  the  circumfer- 
ence of  one  tube.  15  X  12  equals  180  inches  the  length  of  one 

9.4248  X  180 
tube.  • JIT"  "  e(luals  11-781    square  feet  in  one  tube,  and 

11.781  X  50  equals  589.05  square  feet  of  heating  surface  in  fifty 

32  X  3.1416 

tubes.     Then, ^ equals  8.3776  linear  feet  the  circum- 
ference of  the  steam  drum  and  8.3776  X  15  equals  125.664  square 

125.664 
feet  of  heating  surface  in  steam  drum,  and 5 equals  62.832 

square  feet,  half  the  heating  surface  of  steam  drum. 

Then,  589.05  plus  62.832  equals  651.882  square  feet,  the  total 
heating  surface.  Answer. 


STRENGTH  OF  RIVETED  SEAflS. 

The  strength  of  a  riveted  seam  depends  very  much  upon  the 
arrangement  and  proportion  of  the  rivets ;  but  with  the  best 
design  and  construction,  the  seams  are  always  weaker  than  the 
solid  plate,  as  it  is  always  necessary  to  cut  away  a  part  of 
the  plate  for  the  rivet  holes,  which  weakens  the  plate  in  three 
ways:  1st,  by  lessening  the  amount  of  material  to  resist  the 
strains ;  2d,  by  weakening  that  left  between  the  holes ;  3d,  by 
disturbing  the  uniformity  of  the  distribution  of  the  strains. 


462  HANDBOOK    ON    ENGINEERING. 

COMPARATIVE  STRENGTH  OF  SINGLE  AND  DOUBLE 
RIVETED  SEAMS. 

On  comparing  the  strength  of  plates  with  riveted  joints,  it  will 
be  necessary  to  examine  the  sectional  areas  taken  in  a  line  through 
the  rivet  holes,  with  the  section  of  the  plates  themselves.  It  is 
obvious  that  in  perforating  a  line  of  .holes  along  the  edge  of  a 
plate,  we  must  reduce  its  strength.  It  is  also  clear  that  the  plate 
so  perforated  will  be  to  the  plate  itself  nearly  as  the  areas  of  their 
respective  sections,  with  a  small  deduction  for  the  irregularities 
of  the  pressure  of  the  rivets  upon  the  plate ;  or,  in  other  words, 
the  joint  will  be  reduced  in  strength  somewhat  more  than  in  the 
ratio  of  its  section  through  that  line  to  the  solid  section  of  the 
plate.  It  is  also  evident  that  the  rivets  cannot  add  to  the  strength 
of  the  plates,  their  object  being  to  keep  the  two  surfaces  of  the 
lap  in  contact.  When  this  great  deterioration  of  strength  at  the 
joint  is  taken  into  account,  it  cannot  but  be  of  the  greatest 
importance  that  in  structures  subject  to  such  violent  strains  as 
boilers,  the  strongest  method  of  riveting  should  be  adopted.  To 
ascertain  this,  a  long  series  of  experiments  was  undertaken  by 
Mr0  Fairbairn.  There  are  two  kinds  of  lap  joints,  single  and 
double  riveted.  In  the  early  days  of  steam-boiler  construction, 
the  former  were  almost  universally  employed ;  but  the  greater 
strength  of  the  latter  has  since  led  to  their  general  adoption  for 
all  boilers  intended  to  sustain  a  high  steam  pressure.  A  riveted 
joint  generally  gives  way  either  by  shearing  off  the  rivets  in  the 
middle  of  their  length,  or  by  tearing  through  one  of  the  plates  in 
the  line  of  the  rivets. 

In  a  perfect  joint,  the  rivets  should  be  on  the  point  of  shearing 
just  as  the  plates  were  about  to  tear ;  but,  in  practice,  the  rivets 
are  usually  made  slightly  too  strong.  Hence,  it  is  an  established 
rule  to  employ  a  certain  number  of  rivets  per  linear  foot,  which 
for  ordinary  diameters  and  average  thickness  of  plate,  are  about 


HANDBOOK    ON    ENGINEERING.  463 

six  per  foot  or  two  inches  from  center  to  center ;  for  larger 
diameters  and  heavier  iron,  the  distance  between  the  centers 
is  generally  increased  to,  say  2  j-  or  2i  inches :  but  in  such 
cases  it  is  also  necessary  to  increase  the  diameter  of  the  rivet, 
for  while  |,  or  even  J  inch  rivets  will  answer  for  small  diameters 
and  light  plate,  with  large  diameters  and  heavy  plate,  experi- 
ence has  shown  it  to  be  necessary  to  use  f  to  J  rivets.  If 
these  are  placed  in  a  single  row,  the  rivet  holes  so  nearly 
approach  each  other  that  the  strength  of  the  plates  is  much 
reduced ;  but  if  they  are  arranged  in  two  lines,  a  greater  number 
may  be  used,  more  space  left  between  the  holes  and  greater 
strength  aud  stiffness  imparted  to  the  plates  at  the  joint. 
Taking  the  value  of  the  plate  before  being  punched,  at  100,  by 
punching  the  plate  it  loses  44  per  cent  of  its  strength ;  and,  as  a 
result,  single-riveted  seams  are  equal  to  56  per  cent,  and  double- 
riveted  seams  to  70  per  cent  of  the  original  strength  of  the  plate. 
It  has  been  shown  by  very  extensive  experiments  at  the  Brooklyn 
Navy  Yard,  and  also  at  the  Stevens  Institute  of  Technology, 
Hoboken,  N.  J.,  that  double-riveted  seams  are  from  16  to  20  per 
cent  stronger  than  single-riveted  seams  —  the  material  and  work- 
manship being  the  same  in  both  cases : 

Taking  the  strength  of  the  plate  at "    .  100 

The  strength  of  the  double-riveted  joint  would  then  be  .     .       70 
The  strength  of  the  single-riveted  would  be 56 

To  find  the  thickness  of  plates  for  the  shell  of  a  cylindrical 
boiler  for  a  required  safe  working  pressure  in  pounds  per  square 
inch :  — 

Rule*  —  Multiply  the  required  pressure  per  square  inch  by  the 
radius  of  the  shell  in  inches,  and  by  the  constant  number  6  for 
single  riveted  side  seams,  and  divide  the  last  product  by  the 
tensile  strength  of  the  plates.  For  double  riveted  side  seams  use 
the  constant  number  5  instead  of  6. 

Example  J*  —  What  should  be  the  thickness  of  plates  for  a  boiler 
60  inches  in  diameter,  with  single  riveted  side  seams,  for  a  work- 


464 


HANDBOOK   ON    ENGINEERING. 


ing  pressure  of  125  pounds  per  square  inch,  the  tensile  strength 
of  the  plates  being  60,000  pounds  per  square  inch? 

125  X  30  X  6 
Operation*  —  --  6Q  QQQ  --  equals  .375  or  3/8  in.     Answer. 

Example  2*  —  What  should   be  the  thickness  of  plates  for  a 
boiler  60  inches  diameter,  with  double  riveted  side  seams,  for  a 
working   pressure   of    150   pounds   per  square  inch,  the  tensile 
strength  of  plates  being  60,000  pounds  per  square  inch. 
150  X  30  X  5 

Operation*  —  --  60~000  -  e(luals  -375  or  3/8  in.     Answer. 

The  following  formulas*  equivalent  to  those  of  the  British 
Board  of  Trade,  are  given  for  the  determination  of  the  pitch, 
distance  between  rows  of  rivets,  diagonal  pitch,  maximum  pitch, 
and  distance  from  centers  of  rivets  to  edge  of  lap  of  single  and 
double  riveted  lap  joints,  for  both  iron  and  steel  boilers:  — 

Let  p  =  greatest  pitch  of  rivets,  in  inches  ; 
n  =  number  of  rivets,  in  one  pitch  ; 
jpd  =  diagonal  pitch,  in  inches  ; 
d  =  diameter  of  rivets,  in  inches  ; 
T  =  thickness  of  plate,  in  inches; 
V=  distance  between  rows  of  rivets,  in  inches  ; 
E  =  distance  from  edge  of  plate  to  center  of  rivet,  in  inches. 

TO   DETERMINE   THE   PITCH. 

• 

Iron  plates  and  iron  rivets  — 

^X.7854Xtt  f 
P=-       —%,—     -  +  ef  . 

Example  :  First,  for  single-riveted  joint  — 
Given,   thickness  of   plate    (T)=£  inch,  diameter  of  rivet 
(d)  =  £  inch.     In  this  case,  n  =  I.     Required,  the  pitch. 
Substituting  in  formula,  and  performing  operation  indicated. 


Piteh  =  +  f  =  2.077  inches. 


HANDBOOK    ON    ENGINEERING.  465 

For  double-riveted  joint  — 

Given,  t  =  £  inch,  and  d  =  $%  inch.  In  this  case,  n  =  2. 
Then  — 

Pitch  =  (il)'X.7854X2     ,      _  2>886  ^ 

^ 

For  steel  plates  and  steel  rivets  :  — 

28  X  «P  X  »   ,    . 

P~-        28  XT     +  d" 

Example,  for  single-riveted  joint  :  Given,  thickness  of  plate  =  \ 
inch,  diameter  of  rivet  —  -^f  inch.  In  this  case,  n  =  l. 
Then  — 


Example,  for  double-riveted  joint  :  Given,  thickness  of  plate  — 
inch,  diameter  of  rivet  —  J  inch,     n  =  2.     Then  — 

2  +    =  2.85  inches. 


FOR    DISTANCE    FROM    CENTER    OF    RIVET    TO    EDGE    OF    LAP. 

v     3X<* 
E=  ~^ 

Example  :  Given,  diameter  of  rivet  (d)  =|  inch  ;  required,  the 
distance  from  center  of  rivet  to  edge  of  plate. 

E  =  ^^=  1.312  inches, 
2 

for  single  or  double  riveted  lap  joint. 

FOR    DISTANCE    BETWEEN    ROWS    OF    RIVETS. 

The  distance  between  lines  of  centers  of  rows  of  rivets  for 
double,  chain-riveted  joints  (F)  should  not  be  less  than  twice  the 
diameter  of  rivet,  but  it  is  more  desirable  that  V  should  not  be 

i        4*      M  •+  * 
less  than  —  -  —  • 


466  HANDBOOK    ON    ENGINEERING . 

Example  under  latter  formula:   Given,  diameter  of  rivet  —  | 
inch,  then — 

F^(4X|)  +  1  =  2.25  inches. 
For  ordinary,  double,  zigzag -riveted  joints, 

V=^ 


10 

Example :   Given,  pitch  =  2.85  inches,  and  diameter  of  rivet  =  J 
inch,  then  — 


V  (11  X  2.85  +4  X|)  (2.85  +4  X  |)       '' 

—    —  -  =  1. 


.„.     .    , 
487  inches. 


DIAGONAL    PITCH. 

For  double,  zigzag-riveted  lap  joint.     Iron  and  steel. 


Example:   Given,  pitch  =  2.  85  inches,  and  eZ  —  J  inch,  then  — 


j 

MAXIMUM    PITCHES    FOR    RIVETED    LAP    JOINTS. 

For  single-riveted  lap  joints,  maximum  pitch  =(1.31  X 

For  double-riveted  lap  joints,  maximum  pitch  =(2.62  X  T)  -f  If. 

Example:  Given  a  thickness  of  plate  =  %  inch,  required,  the 
maximum  pitch  allowable. 

For  single-riveted  lap  joint,  maximum  pitch  =  (1.31  X  i)  + 
If  =  2.28  inches. 

For  double-riveted  lap  joint,  maximum  pitch  =  (2.62  X  i)  + 
If  =  2.  935  inches. 

The  following  tables,  taken  from  the  handbook  of  Thomas  W. 
Traill,  entitled  "Boilers,  Marine  and  Land,  their  Construction 


HANDBOOK    ON    ENGINEERING. 


467 


and  Strength,"  may  be  taken  for  use  in  single  and  double  riveted 
joints,  as  approximating  the  formulas  of  the  British  Board  of 
Trade  for  such  joints :  — 


IRON  PLATES  AND   IRON  RIVETS. 

DOUBLK-RIVKTED    LAP    JOINTS. 


Thickness 
of  plates. 

Diameter 
of  rivets. 

Pitch  of 
rivets. 

Center  of 
rivets  to 
edge  of 
plates. 

Distance  between  rows 
of  rivets. 

Zigzag 
riveting. 

Chain 
riveting. 

T 

d 

P 

E 

V 

V 

A 

1 

2.272 

.937 

1.145 

1.750 

32 

tt 

2.386 

.984 

1.202 

1.812 

f 

n 

2.500 

1.031 

.    .260 

1.875 

it 

.23 

i2 

2.613 

1.078 

.317 

1.937 

Jv 

2.727 

1.125 

.374 

2.000 

1 

i| 

2.826 

.171 

.426 

2.062 

jj- 

2.886 

.218 

.465 

2.125 

H 

J 

2.948 

.265 

.504 

2.187 

ft 

3.013 

.312 

.544 

2.250 

if 

Sf 

3.079 

.359 

.585 

2.312 

1 

3.146 

.406 

.626 

2.375 

ft 

3.216 

.453 

.667' 

2.437 

1                    3.284 

.500 

.709 

2.500 

fl 

1A                3.355 

.546 

.751 

2.562 

1 

1A                3.426 

.593 

.794 

2.625 

if 

1A               3.498 

.640 

.836 

2.687 

1$ 

H                 3.571 

.687 

1.879 

2.750 

fj 

1A               3.645 

.734 

1.923 

2.812 

{ 

1A                3.718 

.781 

1.966 

2.875 

H 

iA               3.793 

.828 

2.009 

2.937 

II 

U                 3.867 

.875 

2.053 

3.000 

ft 

1A                3.942 

.921 

2.096 

3.062 

i 

1A 

4.018 

1.968 

2.140 

3*125 

On  the  following  page,  Fig.  257  shows  a  zigzag,  and  Fig.  258 
a  chain  riveted  joint. 


468 


HANDBOOK   ON   ENGINEERING. 


[ 

I 

-  -f — t-4. -.- — I — -  ... 

I  I 

6   -<±>-- 
)    O    4 


Fig.  257.    Zigzag  rireted  joint. 


o  -e- 


Fig.  258.    Chain  riveted  joint. 


HANDBOOK   ON   ENGINEERING. 

IRON  PLATES  AND  IRON   RIVETS. 
SINGLE-KIVETED  LAP  JOINTS, 


469 


CD 


__*— 


Thickness  of 
plates. 

Diameter  of 
rivets. 

Pitch  of 
rivets. 

Center  of  rivets  to 
edge  of  plates. 

T 

d 

.P 

E 

«' 

r 

.524 

.937 

T 

\ 

.600 
.676 
.753 

.984 
.031 
.078 

| 

.829 

.125 

• 

I 

!4 

.905 

•171 

• 

v 

1 

1.981 

.218 

- 

i 

"L 

2.036 

.265 

. 

2.077 

.312 

** 

\\ 

2.120 

.359 

*g 

ft 

2.164 

.406 

I 

If 

2.210 

.453 

2.256 

.500 

I 

1 

iA- 
2 

A 

2.304 
2.352 
2.400 

.546 
.593 
.640 

] 

I 

2.450 

.687 

; 

1 

A 

2.500 

.734 

', 

1 

2.550 

.781 

. 

| 

2.601 

.828 

' 

2.652 

1.875 

1 

s 

2.703 
2.755 

1.921 
1.968 

470  HANDBOOK   ON    ENGINEERING. 

STEEL  PLATE  AND  STEEL  RjVETS. 

SINGLE-RIVETED   LAP   JOINTS. 


.  —  t  ------  ,  --- 

\ 


O 


ET 

• 

•?(""• 

\E 


Thickness  of 
plates. 

Diameter  of 
rivets. 

Pitch  of 
rivets. 

Center  of  rivets 
to  edge  of 
plates. 

r 

<* 

P 

E 

1 

Ll 

1.562 

.031 

A 

i 

i 

1.633 

.078 

A 

! 

1.704 

.125 

H 

i                           1.775 

.171 

I 

^ 

| 

1.846 

.218 

¥ 

^ 

J- 

1.917 

.265 

j 

1.988 

.312 

if 

-. 

| 

2.036 

.359 

| 

-| 

2.071 

.406 

iJ 

i 

i 

2.108 

.453 

iff 

f 

2.146 

.500 

II 

1-3 

L2 

2.186 

.546 

I* 

2.227 

.593 

21 

J 

S 

2.269 

.640 

Ll 

1 

2.312 

.687 

32 

A 

2.356 

.734 

| 

j 

s 

2.400 

.781 

32 

! 

5 

2.445 

.828 

1$ 

S 

2.500 

.875 

32 

12 

a2 

2.562 

.921 

| 

1, 

4 

2.623 

.968 

II 

ij 

2.687 

2.015 

a 

Q 

2.750 

2.062 

HANDBOOK  .ON   ENGINEERING. 


471 


STEEL  PLATE  AND  STEEL  RIVETS. 

DOUBLE -RIVETED    LAP  JOINTS. 


Distance  between  rows 

Center  of 

of  rivets. 

Thickness 

Diameter 

Pitch  of 

rivets  to 

of  plates. 

of  rivets. 

rivets. 

edge  of 

plates. 

Zigzag 

Chain 

riveting. 

riveting. 

T 

d 

P 

E 

'V 

V 

A 

H 

2.291 

1.031 

1.187 

1.875 

H 

1  1 

2.395 

.078 

1.240 

1.937 

I 

i 

2.500 

.125 

1.295 

2.000 

ii 

II 

2.604 

.171 

1.349 

2.062 

A 

fl 

2.708 

.218 

1.403 

2.125 

15. 

3  2 

•  32" 

2.803 

265 

1.453 

2.187 

£ 

2  850 

.312 

1.487 

2.250 

32f 

2.900 

.359 

1.522 

2.312 

¥ 

if 

2.953 

.406 

1.558 

2.375 

t| 

32 

3.008 

.453 

1.595 

2.437 

1 

1 

3.064 

.500 

1.631 

2.500 

i 

fA 

3.122 
3.181 

.546 
.593 

1.669 
1.707 

2.562 
2.625 

23 
32 

h4 

3.241 

1.640 

1.745 

2.687 

if 

3.302 

1.684 

1.784 

2.750 

If 

3.364 

1.734 

1.823 

2.812 

If 

i-ig. 

3.427 

1.781 

1.863 

2.375 

|1 

i  _  i  . 

3490 

1.828 

1.902T 

2.937 

£- 

3.554 

1.875 

1.942 

3.000 

fl 

r 

3.618 

1.921 

1.981 

3.062 

le 

i-^ 

3.683 

1.968 

2.021 

3.125 

tl 

lit 

3.748 

2.015 

2.061 

3.187 

1 

11 

3.814 

2.062 

2.102 

3.250 

I 

On  the  following  page  Fig.  259  shows  a  zigzag  riveted  joint 
and  Fig.  260  a  chain  riveted  joint  with  steel  plate  and  steel 
rivets. 


472 


HANDBOOK  ON  ENGINEERING. 


;i*~- ?. 


6 


.•-i — 
I 


O 


E 


Fig.  259.    Zigzag  riveted  joint. 


-+- 
I 
I 


O    -0- 


E 

* 

r 


Fig.  260.    Chain  riveted  joint. 


HANDBOOK   ON    ENGINEERING.  473 

STRENGTH  OF  STAYED  AND  FLAT  BOILER  SURFACES. 

The  sheets  that  form  the  sides  of  fire-boxes  are  necessarily 
exposed  to  a  vast  pressure,  therefore,  some  expedient  has  to  be 
devised  to  prevent  the  metal  at  these  parts  from  bulging  out. 
Stay-bolts  are  generally  placed  at  a  distance  of  4£  inches  from 
center  to  center,  all  over  the  surface  of  fire-boxes,  and  thus  the 
expansion  or  bulging  of  one  side  is  prevented  by  the  stiffness  or 
rigidity  of  the  other.  Now,  in  an  arrangement  of  this  kind,  it 
becomes  necessary  to  pay  considerable  attention  to  the  tensile 
strength  of  the  stay-bolts  employed  for  the  above  purpose,  since 
the  ultimate  strength  of  this  part  of  the  boiler  is  now  transferred 
to  them,  it  being  impossible  that  the  boiler  plates  should  give  way 
unless  the  stay-bolts  break  in  the  first  instance.  Accordingly, 
the  experiments  that  have  been  made  by  way  of  test  of  the 
strength  of  stay-bolts,  possess  the  greatest  interest  for  the  practi- 
cal engineer.  Mr.  Fairburn's  experiments  are  particularly  val- 
uable. He  constructed  two  flat  boxes,  22  inches  square.  The 
top  and  bottom  plates  of  one  were  formed  of  £  inch  copper,  and 
of  the  other,  f  inch  iron.  There  was  a  2£  inch  water-space  to  each, 
with  ^|  inch  iron-stays  screwed  into  the  plates  and  riveted  on  the 
ends.  In  the  first  box  the  stays  were  placed  five  inches  from 
center  to  center,  and  the  two  boxes  tested  by  hydraulic  pressure. 
In  the  copper  box,  the  sides  commenced  to  bulge  at  450  Ibs. 
pressure  to  the  sq.  in. ;  and  at  815  Ibs.  pressure  to  the  sq.  in. 
the  box  burst,  by  drawing  the  head  of  one  of  the  stays  through 
the  copper  plate.  In  the  second  box,  the  stays  were  placed  at 
4-inch  centers;  the  bulging  commenced  at  515  Ibs.  pressure  to 
the  sq.  in.  The  pressure  was  continually  augmented  up  to  1,600 
Ibs.  The  bulging  between  the  rivets  at  that  pressure  was  one- 
third  of  an  inch ;  but  still  no  part  of  the  iron  gave  way.  At 
1,625  Ibs.  pressure  the  box  burst,  and  in  precisely  the  same  way 
as  in  the  first  experiment  —  one  of  the  stays  drawing  through  the 


474  HANDBOOK    ON    ENGINEERING. 

iron  plate  and  stripping  the  thread  in  plate.  These  experiments 
prove  a  number  of  facts  of  great  value  and  importance  to  the 
engineer.  In  the  first  place,  they  show  that  with  regard  to  iron 
stay-bolts,  their  tensile  strength  is  at  least  equal  to  the  grip  of 
the  plate. 

The  grip  of  the  copper  bolt  is  evidently  less.  As  each  stay, 
in  the  first  case,  bore  the  pressure  on  an  area  of  5  x  5  —  25  square 
inches,  and  in  the  second  on  an  area  4x4  i=  16  sq.  inches,  the 
total  strains  borne  by  each  stay  were,  for  the  first,  815  x25  = 
20,375  pounds  on  each  stay;  and  for  the  second,  1,625  x  16  = 
26,000  Ibs.  on  each  stay.  These  strains  were  less,  however,  than 
the  tensile  strength  of  the  stays,  which  would  be  about  28,000 
Ibs.  The  properly  stayed  surfaces  are  the  strongest  part  of  boil- 
ers, when  kept  in  good  repair. 

BOILER  STAYS. 

Advantage  is  usually  taken  of  the  self-supporting  property  of 
the  cylinder  and  sphere,  which  enables  them,  in  most  cases,  to  be 
made  sufficiently  strong  without  the  aid  of  stays  or  other  support. 
But  the  absence  of  this  self-sustaining  property  in  flat  surfaces 
necessitates  their  being  strengthened  by  stays  or  other  means. 
Even  where  a  flat  or  slightly  dished  surface  possesses  sufficient 
strength  to  resist  the  actual  pressure  to  which  it  is  subjected,  it  is 
yet  necessary  to  apply  stays  to  provide  against  undue  deflection 
or  distortion,  which  is  liable  to  take  place  to  an  inconvenient  de- 
gree, or  to  result  in  grooving,  long  before  the  strength  of  plates 
or  their  attachments  is  seriously  taxed.  Boiler  stays,  in  any 
case,  are  but  substitutes  for  real  strength  of  construction.  They 
would  be  of  no  service  applied  to  a  sphere  subject  to  internal 
pressure  ;  and  the  power  of  resistance  would  be  exactly  that  of 
the  metal  to  sustain  the  strain  exerted  upon  all  its  parts  alike. 
The  manner  in  which  stays  are  frequently  employed  renders  them 
a  source  of  weakness  rather  than  an  element  of  strength.  When 


HANDBOOK    ON    ENGINEERING. 


475 


the  strain  is  direct  the  power  of  resistance  of  the  stay  is  equal  to 
the  weight  it  would  sustain  without  tearing  it  asunder ;  but  when 
the  position  of  the  stay  is  oblique  to  the  point  of  resistance,  any 
calculation  of  their  theoretic  strength  or  value  is  attended  with 
certain  difficulties.  All  boilers  should  be  sufficiently  stayed  to 
insure  safety,  and  the  material  of  which  they  are  made,  their 
shape,  strength,  number,  location  and  mode  of  attachment  to  the 
boiler,  should  all  be  duly  and  intelligently  considered.  Boiler 
stays  should  never  be  subjected  to  a  strain  of  more  than  one- 
eighth  of  their  breaking  strength.  The  strength  of  boiler  stays 
may  be  calculated  by  multiplying  the  area  in  inches  between  the 
stays  by  the  pressure  in  pounds  per  square  inch. 

Rule  for  finding  the  strain  allowed  on  a  diagonal  boiler  head 
brace  or  stay  ;  also  rule  for  finding  the  number  of  stays  required 
for  a  certain  size  crown  sheet. 

Iron  stays  should  not  be  subjected  to  a  greater  stress  than 
from  7,000  to  9,000  pounds  per  square  inch  of  section,  and  if 
they  are  located  obliquely,  the  diameter  will  need  to  be  increased 
an  amount  that  depends  on  the  angle  of  the  stay  to  the  shell. 
Find  the  area  in  square  inches  to  be  supported  by  the  stay,  and 
multiply  it  by  the  pressure  per  square  inch,  multiply. the  product 
by  the  length  of  the  diagonal  stay,  and  divide  the  result  by  the 
perpendicular  length  from  the  flat  surface  to  the  end  of  the  stay. 
The  quotient  will  be  the  stress  on  the  stay,  and  to  obtain  the 
diameter,  divide  the  stress  by  the  allowable  stress  per  square  inch 

of    section,  and  the  quotient 
mmmm *  by  .7854.     The  square  root  of 

the  last   quotient  will  be  the 

diameter  of  the  stay. 

Thus,  in  the  accompanying 

diagram,  we  wish  to  find  the 

Fis.  261.  Diagonal  boiler  stay,  diameter  of  the  diagonal  stay 
A,  which  supports  an  area  6"  x  8"  or  48  square  inches.  The 


476  HANDBOOK    ON    ENGINEERING. 

length  of  the  stay  is  25",  and  the  perpendicular  distance  be- 
tween the  stayed  surface  and  the  end  of  the  stay  is  24.148". 
The  boiler  pressure  is  100  pounds  gauge,  so  that  the 
pressure  on  the  surface  supported  will  be  48  x  100  or  4,800 
pounds.  We  multiply  4,800  by  25  and  divide  the  product  by 
24.148",  which  gives  4,970,  nearly.  The  quotient  of  4,970, 
divided  by  7,000  equals  .71;  .71,  divided  by  .7854  equals 
.9039,  and  the  square  root  of  this  is  .95  or  .95",  the  diameter  of 
a  stay  that  will  support  48  square  inches  in  the  position  shown. 
A  convenient  formula  for  finding  the  diameter  of  oblique  stays 


D  equals 


cosB 


D  equals  diameter  of  the  stay. 

A      "       area  in  square  inches  to  be  supported. 

P      "       pressure  per  square  inch. 

L      "       safe  load  per  square  inch  of  stay  section. 

B      "       angle  between  the  shell  and  the  stay. 

Using  the  preceding  problem  as  an  example  and  referring  to 
the  same  diagram,  we  have  angle  B  equal  to  15°,  and  all  the  other 
dimensions  as  previously  given.  Therefore, 


T.  ,  Q    J48  X  100 

D  equals  1.13A —  ° 
\  7C 


7000  X  .96593 

The  diameter  of  the  stay,  when  the  above  is  simplified,  is 
.9526",  or  practically  1".  A  rule  for  finding  the  pitch  of  stays 
for  any  flat  surface  is  given  below. 

J.  A  safe  formula  for  the  strength  of  stayed  flat  surfaces  is 
that  given  by  Unwin's  Machine  Design.  When  the  spacing  of 
the  stays  is  desired,  assuming  that  it  is  the  same  in  each  direc- 
tion, we  have, 


a  equals  3  t 


N/Z 
\2  p 


HANDBOOK.  ON    ENGINEERING.  477 

where  a  equals  spacing  of  stays  or  rivets  in  inches,/  equals  safe 
working  strength  of  the  plate,  t  equals  thickness  of  plate,  and  p 
equals  boiler  pressure.  Expressed  as  a  rule,  this  reads  :  Divide 
the  safe  strength  of  the  plate  by  twice  the  pressure  ;  extract  the 
square  root  of  the  quotient  and  multiply  the  final  result  by  three 
times  the  thickness  of  the  plate.  The  result  will  be  the  spacing 
of  the  stays  in  inches.  For  example,  boiler  pressure  100  pounds, 
plate  1/2  inch  thick,  safe  strength  of  plate,  10,000  pounds  per 
square  inch  ;  2j9  equals  2  x  100  equals  200  ;  f/2p  equals  10000/200 
equals  50;  V^O  equals  7.07;  3£  equals  3/2  equals  1-1/2  equals 
1.5;  7.07x1.5  equals  10.6  for  the  spacing.  In  making  such  a 
calculation  care  must  be  exercised  not  to  assume  too  high  values 
for  the  strength  of  the  plate.  It  is  not  safe  to  count  on  more 
than  60,000  pounds  for  the  strength  of  steel  plates  and  40,000 
for  iron.  The  working  strength  must  be  taken  not  higher  than  1/6 
of  this,  or  10,000  for  steel  and  6,666  for  iron,  and  lower  values 
still  would  be  better,  say  9,000  for  steel  and  6,000  for  iron. 

2*  The  safe  pressure  for  a  boiler  to  carry,  so  far  as  the 
flat,  stayed  surfaces  are  concerned,  may  be  found  from  the 
above  formula  by  transposing  it  a  little,  as  follows:  — 

9  Z2/ 
p  equals  ~^T 

Now,  applying  this  to  the  above  example,  we  have  p  equals 
9  x.52  x  10000  9  x  .25  x  10000 


2x110.25  2x110.25 

22500 

duction  equals  ^^-^  equals  102,  or  substantially  the  pressure 
£i  ZO»oO 

assumed  in  the  first  example. 

RIVETED  AND  LAP-WELDED  FLUES. 

The  following  table  shall  include  all  riveted  and  lap-welded 
flues  exceeding  6  inches  in  diameter  and  not  exceeding  40  inches 
in  diameter  not  otherwise  provided  by  law,  as  required  by  U.  S.  Gov. 


478 


HANDBOOK    ON    ENGINEERING. 


CHART  TO  FIND  STEAM  PIPE  NEEDED  FOR  HEATING 
WATER  IN  TANKS 

From  careful  experiments  it  is  found  that  one  square  foot  of 
pipe,  filled  with  steam  and  immersed  in  water,  will  condense 
0.155  Ibs.  of  steam  per  hour  for  each  Faht.  degree  of  difference 
between  the  temperature  of  the  steam  and  the  mean  temperature 
of  the  water.  The  Ideal  Fitter. 

Steam  condensed  per  square  root  01  pipe  per  hour  in  Lbs. 

^  «  N  co  co  •*  o  to'  to'  t^  oo  »  o   o   -'  e;   n  m  •*    o  to   £*   £  oo  »    c   o   -j 
g 


II 


I 


Chart  <fc  A  M 

Example.  —  It  is   required  to  condense  500  Ibs.  of  steam  per 
hour  in  a  pipe  coil  immersed  in  the  water  of  a  storage  tank. 

Temperature  of  steam  in  the  pipe 220 

Initial  temperature  of  the  water 40 

Terminal  temperature  of  the  water 160 

Mean  temperature  of  the  water *  100 

Temp,  difference  between  steam  and  water     .     .     .     120 


HANDBOOK    ON    ENGINEERING.  479 

CHART  TO  FIND  STEAM  PIPE  NEEDED  FOR  HEATING 
WATER  IN  TANKS.  — Continued 

How  many  square  feet  of  pipe  must  the  coil  contain? 

Referring  to  Chart  A,  find  the  horizontal  line  marked  120 
degrees  temperature  difference,  which  intersects  the  diagonal 
line  at  the  vertical  line  reading  18.60  Ibs.  (the  quantity  of  steam 
one  sq.  ft.  will  condense  in  one  hour),  and  as  500  Ibs.  is  to  be 
condensed  divide  500  by  18.60,  which  gives  27  sq.  ft.  of  pipe. 
To  condense  500  Ibs.  in  two  hours  will  require  half  of  27,  or  13.5 
sq.  ft. 

These  experiments  were  made  with  1|  inch  black  iron  pipe. 
Galvanized  iron  pipe  would  doubtless  be  better,  as  it  would  not 
corrode  so  quickly.  Brass  pipe  would  be  the  best  to  use,  not  so 
much  for  its  higher  conductivity  as  for  its  resistance  to  the  action 
of  impure  water. 

I       CHART  TO  FIND  BOILER  POWER  REQUIRED  TO  HEAT 
SWIMMING  POOLS 

In  heating  large  bodies  of  water,  large  boilers  are  employed, 
and  when  anthracite  coal  is  burned  in  them,  there  will  be  avail- 
able, from  each  pound  of  coal  burned,  8333  B.  T.  U.  or  8.6 
Ibs.  water  will  be  evaporated,  and  on  this  basis  the  chart  is  con- 
structed. 

One  square  foot  of  grate  will  burn  8  Ibs.  anthracite  coal  per 
hour,  whieh  is  the  index  for  finding  the  size  boiler  required  for  a 
given  quantity  of  work. 

The  horizontal  lines  on  Chart  "  B  "  represent  water  in  U.  S. 
gallons,  which  may  be  increased  by  any  suitable  multiplier,  pro- 
viding the  coal  and  steam  required  are  increased  in  like  propor- 
tion. 

The  figures  at  the  bottom  of  vertical  lines  show  the  eoal  re- 
quired, each  line  representing  10  Ibs.,  and  those  at  the  top  the 


480 


HANDBOOK    ON    ENGINEERING. 


steam  generated  by  the  combustion  of  the  quantity  of  coal  on  the 
same  vertical  line  —  each  line  representing  86  Ibs.  of  steam. 

The  diagonal  lines  represent  the  rise,  or  increase,  in  tempera- 
ture of  the  water  per  hour  in  Faht.  degrees. 

Water  in  U.  S.  gallons 

iiiiiiiili. 


!(__        I     ip 
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\2&)  '  * 
:j;  =  f|||l::  N$ 

2       *  " 
5"     160  —  j>::  —  zifl;:: 

7c:-_      <:      _,i_^^^7     7^/2       

l:::i^j^z:i^^!  1290 

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/f;::/::/^"^;:::;;::::  1720 

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i:^:^?::::::::::::::::2580^ 

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o    S350::::-:::^::;:::::-:::z 

3    o  400^-"-"---?-  /----/--^ 

i^:::::::::::::::::::::3440* 

0    E.       --^  —  7---  ---Z.___z_.  z!^ 

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L     .     _    D 

CO 

g"  S  5002:::_:  :2.::::z:::::::^: 

:_::"::  :__::__:::_::>:::  4300  S. 

S  5'       7  ;z---z~/z^~~~ 

:::::::::::::::::::::::::473o3 

^  •        :i::::::i::::S--Oi:::::: 

^     flo°  _/  —  z::2ij!  

5160g 

650  ^  2_   tfi*"          ~    I 

__.       ._    _:_:_--__::  5580  ss 

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.     

860-:^:-::=:::::=::::::::::: 

6880 

Chart 


HANDBOOK    ON    ENGINEERING.  481 

CHART  TO  FIND  BOILER  POWER  REQUIRED  TO  HEAT 
SWinniNd  POOLS  — Continued 

Example  1 .  —  What  size  boiler  is  required  to  warm  the  water 
n  a  swimming  pool,  containing  130,000  gallons,  from  40°  to  80Q 
n  24  hours. 


By  reference  to  Chart  B  it  is  found  that  the  horizontal  line 
narked  1000  gallons  intersects  the  40  degree  diagonal  line  at 
;he  40  Ib.  vertical  line,  showing  that  40  Ibs.  of  coal  are  required 
;o  add  40  degrees  to  1000  gallons  of  water.  Then  100,000  gal- 
ons  will  require  100  times  as  much  coal,  or  4000  Ibs.  In  the 
jame  manner  3000  gallons  require  120  Ibs.,  and  30,000 
gallons  will  require  ten  times  120,  or  1200  Ibs.,  making  a  total 
)f  5,200  Ibs.  of  coal  which  must  be  burned  to  add  40  degrees  to 
L30,000  gallons  of  water. 

Having  24  hours  in  which  to  heat  the  pool,  divide  5200  Ibs, 
>y  24,  and  it  is  found  that  216  pounds  of  coal  must  be  burned 
)er  hour  for  24  hours.  Now  as  8  Ibs.  of  coal  is  burned  per 
iour  on  one  sq.  ft.  of  grate,  divide  216  by  8,  which  shows  that 
)oilers  containing  27  sq.  ft.  of  grate  must  be  provided.  Each 
'rate  section  of  the  usual  36  inch  Sectional  Boiler  contains  2 
jq.  ft.  of  grate  and  cast  iron  Sectional  Boilers  have  one  less 
'rate  section  than  the  total  number  of  sections  in  the  boiler. 
Co  obtain  the  27  sq.  ft.  of  grate,  select  two  which  will  have 
14  sq.  ft.  in  each. 

HEATING  POOLS  BY  STEAM  COILS. 

Example  2  —  If  the  pool  is  to  be  heated  by  steam  coils  and 
;he  temperature  of  the  steam  is  215°,  find  the  mean  temperature 
)f  the  water  is  40  +  80  ^-  2  =  60°  and  215  —  60  =  155 
legrees  temperature  difference  between  steam  and  water. 

Turn  to   Chart  A,  which   shows  that   with  this   temperature 


482  HANDBOOK    ON    ENGINEERING. 

difference  1  sq.  ft.  of  pipe  will  condense  24  Ibs.  of  steam  per 
hour,  and  as  216  Ibs.  of  coal  must  be  burned  per  hour,  find  by 
interpolation  in  Chart  B  tha'o  216  Ibs.  of  coal  will  evaporate 
1857  Ibs.  steam,  which  divide  by  24  and  find  shall  require  in 
round  figures  78  sq.  ft.  of  condensing  pipe  in  the  pool.  The 
boilers  will  be  the  same  size  as  for  water. 

78  sq.  ft.  is  equal  to  180  linear  feet  of  1£  in.  pipe,  156  ft.  1£ 
in.,  or  125  ft.  of  2  in.  If  but  12  hours  can  be  allowed  to  do  the 
work,  double  the  hourly  consumption  of  coal  and  steam  and 
furnish  boilers  of  double  the  capacity  required  for  24  hours'  time. 

CHART  TO  FIND  BOILER  POWER  REQUIRED  TO  HEAT 
SWIMMING  POOLS  —  Continued. 

As  there  will  now  be  twice  as  much  steam  to  condense  in  an 
hour,  double  the  quantity  of  condensing  coil. 

There  is,  however,  another  factor  which  must  not  be  overlooked. 

In  large  bodies  of  water,  warmed  in  the  manner  just  described, 
there  will  be  a  zone,  of  which  the  condensing  pipe  is  the  center, 
where  the  mean  temperature  of  the  water  will  be  much  higher 
than  figured  in  the  foregoing,  unless  artificial  means  are  em- 
ployed to  agitate  the  water  and  keep  it  all  at  an  even  tempera- 
ture. It  will,  therefore,  be  good  practice  to  add  at  least  50  per 
cent  to  the  condensing  coil  when  used  in  large  bodies  of  still  water. 

CHART  TO  FIND  TANK  HEATER  CAPACITY  FOR  RAISING 
WATER  IN  TANKS  TO  A  SPECIFIC  TEMPERATURE. 

Power  in  small  tank  heaters,  7000  B.  T.  U.  per  pound  coal: 

Size  round  grate  in  tank  heaters    10"  12"   15"    18"  21"    24"    27"    30" 

Average  hard  coal  capacity,  Ibs.     25  40      75    120180225    300    370 

Average  h'd  coal  available,  Ibs.     20  32      60      96  145  180    240    300 

Max  coal  consump'n  per  hr.,  Ibs.  4.4  6.310       14    16.325      32      40 

(8  Ibs.  persq.  ft.  grate  per  hr.) 

Duration  of  fire,  hrs.  in  decimals,  4.5  5.1     6.      6.8     6.9    7.2     7.5     7.5. 

Example:  What  size  tank  heater  running  at  maximum  ca- 
pacity will  add  140  degrees  to  120  gallons  of  water  in  one  hour? 
By  referring  to  Chart  "  C"  we  find  the  120  gallon  horizontal 

" 


HANDBOOK    ON    ENGINEERING. 


483 


line  intersects  the  140  degrees  temperature  line  at  the  20  pound 
vertical  coal  line,  and  a  reference  to  data  at  bottom  of  Chart 
"  C  "  shows  that  a  heater  with  24-inch  grate  will  burn  25  pounds 
coal  per  hour  running  at  maximum  capacity,  which  would  be  the 
correct  size  to  select. 

The  figures  on  Chart  "  C  "  are  based  on  the  work  being  ac- 
complished in  one  hour,  and  in  the  above  example  20  pounds  of 
coal  must  be  burned  in  one  hour  to  produce  the  required  energy, 
but  it  is  obvious  that  20  pounds  of  fuel  must  be  used  whether 
the  work  is  done  in  one  or  ten  hours.  If  the  time  is  two  hours, 
select  a  heater  that  will  burn  10  pounds  per  hour,  or  a  15-inch 
grate.  The  10-inch  grate  will  do  the  work  in  4*  hours;  the  12 
inch  grate  in  4  hours. 


POUNDS  or  ANTHBACrrt  COAL  RtQumco  pen  noun 


POUNDS  Of  AyHMOTC  tjOM,  REQUIUCO  Ptff   MOU«  . 

Chart  "C." 

CHART    TO    FIND    TANK    HEATER   CAPACITY   FOR    RAISING 
WATER  IN  TANKS  TO  A  SPECIFIC  TEflPERATURE. 


484  HANDBOOK  ON  ENGINEERING. 

The  vertical  lines  represent  coal  in  pounds.  The  horizontal 
lines  represent  water  in  gallons.  The  diagonal  lines  represent 
temperatures. 

DATA  RELATING  TO  VENTILATION. 

Loss  of  heat  caused  by  — 

First.      B.  T.  U.  necessary  to  warm  air. 

Second.  B.  T.  U.  absorbed  by  walls. 

Third.     B.  T.  U.  absorbed  by  ceiling. 

Fourth.    B.  T.  U.  absorbed  by  floor. 

Fifth.       B.  T.  U.  absorbed  by  windows. 

Sources  of  heat  in  rooms  (Schuman,  authority)  :  — 

First.      B.  T.  U.  generated  by  occupants. 

Second.  B.  T.  U.  generated  by  gas,  lamps  or  candles. 

Third.     B.  T.  U.  generated  by  heating  apparatus. 

An  adult  requires  each  hour  for  respiration  and  transpiration 
215  cubic  feet  or  215x.077  =  165  pounds,  and  generates  290 
B.  T.  U.  of  which  99  units  are  in  form  of  vapor  and  191  units 
radiate  to  surrounding  objects. 

APPROXIflATE. 

An  adult  vitiates  per  hour  2.15  cu.  ft.  air. 

Each  cubic  ft.  gas  burned  requires  8.5  cu.  ft.  air. 

Each  Ib.  oil  burned  requires  150  cu.  ft.  air. 

Each  Ib.  candles  burned  requires  160  cu.  ft.  air. 

B.  T.  U.  generated  by  an  adult  per  hour,  191. 

B.  T.  U.  generated  by  burning  l.cu.  ft.  gas,  600. 

B.  T.  U.  generated  by  burning  1  Ib.  oil  or  candles,    15,000  to 

18,000. 

Average  gas  burner  consumes  approximately  4  cu.   ft.   gas  per 
hour,  which  equals  2400  B.  T.  U.  per  hour. 
Each  flame  from  oil  lamp  430  to  515  B.  T.  U.  per  hour. 
Each  candle  454  to  545  B.  T.  U.  per  hour. 

NOTE.  —  Above  information  is  quoted  from  standard  authorities. 
Not  guaranteed. 


HANDBOOK  -ON    ENGINEERING. 


485 


Table  of  Mains  and  Branches 


Main 

1  in.  will  supply  2 
IJin. 

14  in. 

2  in. 
24  in. 

3  in. 
3£  in. 

'4    in. 
44  in. 

5  in. 

6  in. 

7  in. 

8  in. 


Branch 


fl 

a 

2 

2 
1 
2 
1 
1 
1 
2 
1 
2 

24 
24 

34 

34 
4 
4 
6 
6 

in. 
in. 
in. 
in. 
in. 
in. 
in. 
in. 
in. 

and 
and 
or 
and 
and 
and 
and 
and 
and 

1 
1 

1 
1 
1 
1 
1 
1 
1 

1; 
2 

3 
2 
3 
3 
3 
4 
5 

H 
i 
in 

£i 
in 
in 
in 
in 
in 

Q. 

n. 

y 

•) 

'j 

•3 
') 
•1 

,  or  1 
,  or  2 
and  1 
,  or  2 
or  1 
cr  1 
or  4 
or  3 
or  5 

2 
2 
2 
3 
4 

3 
4 
4 

in. 
in. 
in. 
in. 
in. 

in. 
in. 
in. 

and  1 
and  1 
or    3 
and  4 
and  1 
and  1 
or  10 
and  1 
and  2 

|in. 

1  in. 
llin. 
14  in. 
IJin. 
14  in. 

2  in. 
2    in. 
2£  in. 
2£  in. 
2    in. 
2    in. 
2    in. 


Capacities  of  Wrought  Iron  Pipe 


Inside  diameter  Inches 

1 

U 

14 

2 

24 

3 

34 

4 

5 

6 

Length  of  Pipe           ^ 

per  square  foot  of  > 

2.9 

2.3 

2.0 

1.6 

1.32 

1.09 

0.95 

0.84 

0.68 

0.57 

external  surface     J 

Square  feet;  surface  \ 
per  1  lineal  foot     J 

0.34 

0.43 

0.50 

0.62 

0.75 

0.92 

1.05 

1.18 

Ml 

1.74 

Expansion  of  Wrought  Iron  Pipe 


Temperature 
of  the  Air 
when 
Pipe  is  fitted 

Length  of 
Pipe  when 
fitted 

Length  of  Pipe  when  heated  to 

215° 

265° 

297° 

338° 

Zero 

100  feet 

Ft.     In. 
100    1.72 

Ft.     In. 

100   2.12 

Ft.     In. 
100   2.31 

Ft.     In. 
100   2.70 

32° 

100    " 

100   1.47 

100    1.78 

100   2.12 

100   2.45 

64° 

100    " 

100    1.21 

100    1.61 

100    1.87 

100   2.19 

486 


HANDBOOK   ON   ENGINEERING. 


firmly  riveted ,  with  good  and  substantial  rivets,  through  the  hubs 
of  such  flanges  ;  and  no  such  hubs  shall  project  from  such  flanges 
less  than  2  inches  in  any  case. 

Steam  pipes  of  iron  or  steel,  when  lap- welded  by  hand  or 
machine,  with  their  flanges  welded  on,  shall  be  tested  to  a  hydro- 
static pressure  of  at  least  double  the  working  pressure  of  the 
steam  to  be  carried  and  properly  annealed  after  all  the  work 
requiring  fire  is  finished.  When  an  affidavit  of  the  manufacturer 
is  furnished  that  such  test  has  been  made  and  annealed,  they  may 
be  used  for  power  purposes. 

WROUGHT    IRON    WELDED    PIPE. 

DIMENSIONS,    WEIGHTS,    ETC.,    OF    STANDARD    SIZES  FOR  STEAM,  GAS, 
WATER,    OIL,    ETC. 

1  inch  and  below  are  butt- welded,  and  tested  to  300  pounds 
per  square  inch  hydraulic  pressure. 

1J  inch  and  above  are  lap-welded,  and  tested  to  500  pounds 
per  square  inch  hydraulic  pressure. 


i 

5 

utside  Di- 
ameter. 

xternal  Cir- 
jumference. 

o  c3  *""£ 

li 

I* 

xternal 
Area. 

Bngth  of 
Pipe  con- 
taining one 
cubic  foot.  1 

reight  per 
:t.  of  length. 

o.of  threads!  1 
per  inch  of 
screw. 

intents  in 
*Gallons 
per  foot. 

"eight  of 
Water  per 
foot  of 
Length. 

O 

0 

H 

h-3 

H 

3 

j£- 

K 

O 

& 

Inch. 

Inches. 

Inches. 

Feet. 

Inches. 

Inches. 

Feet. 

Lbs. 

Lbs. 

§ 

40 

1.272 

9  44 

.012 

.129 

2500. 

.24 

27 

.0006 

.005 

I 

.54 

1.696 

7.075 

049 

229 

1385. 

.42 

18 

.0026 

.021 

.67 

2  .  121 

5.657 

.110 

.358 

751.5 

.56 

18 

.0057 

.047 

I 

.84 

2.652 

4  502 

.196 

.554 

472.4 

.84 

14 

.0102 

.085 

1.05 

3  299 

3.637 

.441 

.866 

270. 

1.12 

14 

.0230 

.190 

I1 

1  31 

4.134 

2.903 

.785 

1.357 

166.9 

1.67 

iii 

.0408 

.349 

}j 

1  66 

5.215 

2.301 

1  227 

2.164 

96.25 

2.25 

.0638 

.527 

1.9 

5.969 

2.01 

1.767 

2.835 

70.65 

2.69 

jj  i 

.0918 

.760 

2 

2.37 

7.461 

1.611 

3.141 

4.430 

42.36 

3.66 

iis 

.1632 

1.356 

2» 

2.87 

9.032 

1.328 

4  908 

6.491 

30.11 

5.77 

8 

.2550 

2.116 

3 

3  5 

10.996 

1  091 

7.068 

9.621 

19.49 

7.54 

8 

.3673 

3.049 

34 

4. 

12.566 

.955 

9.621 

12.566 

14.56 

9.05 

8 

.4998 

4.155 

4 

4.5 

14.137 

.849 

12.566 

15.904 

11.31 

10.72 

8 

.6528 

5.405 

5. 

15.708 

.765 

15.904 

19.635 

9.03 

12.49 

8 

.8263 

6.851 

5 

5  56 

17.475 

.629 

19.635 

24.299 

7.20 

14.56 

8 

1.020 

8.500 

6 

6.62 

20.813 

.577 

28.274 

34.471 

4.98 

18.76 

8 

1.469 

12.312 

7 

7.62 

23  954 

.505 

38.484 

45.663 

3.72 

23.41 

8 

1.999 

16.662 

8 

8.62 

27.096 

.444 

50.265 

58.426 

2.88 

28.34 

8 

2.611 

21.750 

9 

9  68 

30.433 

.394 

63.617 

73.715 

2,26 

34.67 

8 

3.300 

27.500 

10 

10.75 

33.772 

.355 

78.540 

90.792 

1.80 

40.64 

8 

4.081 

34.000 

HANDBOOK   ON    ENGINEERING. 


487 


PULSATION  IN  STEAfl-BOILERS. 

Pulsation  in  steam-boilers,  though  not  discernible  to  the  eye, 
as  in  animated  nature,  goes  on  intermittently  in  some  boilers 
whenever  they  are  in  use.  It  is  induced  by  weakness  and  want 
of  capacity  in  the  boiler  to  supply  the  necessary  quantity  of 
steam,  and  sometimes  is  caused  by  the  boiler  being  badly  de- 
signed, thereby  admitting  of  a  great  disproportion  between  the 
heating-surface  and  steam-room.  Boilers  are  frequently  found  in 
factories  that  were  originally  not  more  than  of  sufficient  capacity 
to  furnish  the  necessary  quantity  of  steam,  but,  as  business 
increased,  it  became  necessary  to  increase  the  pressure  and  also 
the  speed  of  the  engine ;  or,  perhaps  to  replace  it  with  a  larger 
one,  which  has  to  be  supplied  with  steam  from  the  same  boiler. 
The  result  is,  each  time  the  valve  opens  to  admit  steam  to  the 
cylinder,  about  one-third  of  the  whole  quantity  in  the  boiler  is 
admitted,  thus  lowering  the  pressure  ;  the  next  instant,  under  the 
influence  of  hard  firing,  or,  perhaps,  a  forced  draught,  the  steam 
is  brought  to  the  former  pressure,  and  so  on  ;  this  lessening  and 
increasing  the  pressure  continues  while  the  engine  is  in  motion, 
which  has  an  effect  on  the  boiler  similar  to  the  breathing  of  an 
animal. 

The  strains  induced  By  this  pulsation  are  transmitted  to  the 
weakest  places,  viz.,  the  line  of  the  rivet  holes,  and  that  marked 

by  the  tool  in  the  process  of 
calking  ;  the  result  is,  the  plate 
is  broken  in  two,  as  shown  in 
the  above  cut.  The  manner  in 
which  the  break  takes  place 
may  be  illustrated  by  filing  a 
small  nick,  or  drilling  a  small 
hole,  in  a  piece  of  hoop  or  band- 
iron,  and  then  bending  back 
Fig.  262.  Cracked  plate. 


488 


HANDBOOK   ON    ENGINEERING. 


and  forth,  when  it  will  be  discovered  that  the  material  will  break 
just  at  that  point,  however  slight  the  nick  or  small  the  hole  may 
be.  Pulsation  is  frequently  very  severe  in  the  boilers  of  tug- 
boats when  commencing  to  start  a  heavy  tow,  and  also  in  loco- 
motives when  starting  long  trains.  Some  frightful  explosions  of 
the  boilers  of  tug-boats  and  locomotives  have  occurred  under 
such  circumstances.  Pulsation,  if  permitted  to  continue,  is  sure 
to  effect  the  destruction  of  the  boiler.  It  is  always  made  mani- 
fest by  the  vibrations  of  the  pointers  on  steam  gauges,  or  an 
unsteadiness  in  the  mercury  column.  It  may  be  remedied,  to  a 
certain  extent,  by  adding  a  larger  steam  dome,  but  this  has  a 
tendency  to  weaken  the  boiler  and  render  it  more  unsafe.  The 
only  sure  preventive  of  such  a  silent  and  destructive  agent  is  to 
have  the  boiler  of  sufficient  capacity  in  the  first  place. 


WEIGHT    OF    SQUARE    AND    ROUND    IRON   PER   LINEAR    FOOT. 


SIDE 
OR 
DIAM. 

Weight, 
Square. 

Weight, 
Round. 

SIDE 
OR 
DIAM. 

Weight, 
Square. 

Weight. 
Round. 

SIDE 
OR 
DIAM. 

Weight, 
Square. 

Weight, 
Round. 

iV 

.013 

.01 

2 

13.52 

10.616 

5 

84.48 

66.35 

? 

.053 

.041 

i 

15.263 

11.988 

* 

93.168 

73.172 

iV 

.118 

.093 

17.112 

13.44 

I 

102.24 

80.304 

1 

.211 

,165 

i 

19.066 

14.975 

1 

111.756 

87.776 

.475 

.373 

I 

21.12 

16.588 

I 

.845 

.663 

i 

23.292 

18.293 

6 

121.664 

95.552 

1.32 

1.043 

i 

25.56 

20.076 

\ 

132.04 

103.704 

1 

1.901 

1.493 

i 

27.939 

21.944 

i 

142.816 

112.16 

I 

2.588 

2.032 

154.012 

120.96 

3 

30.416 

23.888 

i 

3.38 

2.654 

i 

35.704 

28.04 

7 

165.632 

130.048 

I 

4.278 

3.359 

* 

41.408 

32.515 

\ 

177.672 

139.544 

5.28 

4.147 

47.534 

37.332 

i 

190.136 

149.328 

1 

6.39 

5.019 

203.024 

159.456 

£ 

7.604 

5.972 

4 

54.084 

42.464 

$ 

8.926 

7.01 

i? 

61.055 

47.952 

8 

216.336 

169.856 

1 

10.352 

8.128 

h 

68.448 

53.76 

1 

11.883 

9333 

\ 

76.264 

59.9 

9 

273.792 

215.04 

HANDBOOK  ON   ENGINEERING.  489 

WATER  COLUHNS. 

Every  boiler  should  be  equipped  with  a  safety  water  column. 
Next  to  keeping  the  steam  pressure  within  the  limits  of  safety, 
the  most  important  point  to  be  observed  in  operating  steam  boilers 
is  the  maintenance  of  the  proper  water  level.  If  the  water  level 
is  too  low,  there  is  danger  of  burning  the  tubes  and  plates  and? 
perhaps,  of  wrecking  the  boiler ;  if  it  is  too  high,  water  is  liable  to 
be  carried  along  with  the  steam  and  cause  damage  in  the  engine, 
while  a  constant  variation  in  the  water  level  produces  a  waste  of  fuel 
and  unsteady  pressure,  and  impairs  the  life  of  the  boiler.  Safety 
water  columns  have  been  devised  for  the  purpose  of  insuring  owners 
of  steam  boilers  against  accidents  of  this  kind.  They  are  so  ar- 
ranged that  any  variation  in  the  water  level  beyond  reasonable  lim- 
its will  be  loudly  proclaimed  by  means  of  a  suitable  steam  whistle. 

STEAM-GAUGES. 

The  object  of  the  steam-gauge  is  to  indicate  the  steam  pressure 
in  the  boiler,  in  order  that  it  may  not  be  increased  far  above  that 
at  which  the  boiler  was  originally  considered  safe  ;  and  it  is  as  a 
provision  against  this  contingency  that  a  really  good  gauge  is  a 
necessity  where  steam  is  employed,  for  no  guide  at  all  is  vastly 
better  than  a  false  one.  The  most  essential  requisites  of  a  good 
steam-gauge  are,  that  it  be  accurately  graduated,  and  that  the 
material  and  workmanship  be  such  that  no  sensible  deterioration 
may  take  place  in  the  course  of  its  ordinary  use.  The  pecuniary 
loss  arising  from  any  considerable  fluctuation  of  the  pressure  of 
steam  has  never  been  properly  considered  by  the  proprietors  of 
engines.  If  steam  be  carried  too  high,  the  surplus  will  escape 
through  the  safety-valve,  and  all  the  fuel  consumed  to  produce 
such  excess  is  so  much  dead  loss.  On  the  other  hand,  if  there  be 
at  any  time  too  little  steam,  the  engine  will  run  too  slow,  and 
every  lathe,  loom,  or  other  machine  driven  by  it,  will  lose  its 
speed  and,  of  course,  its  effective  power  in  the  same  pro- 


490  HANDBOOK    ON    ENGINEERING. 

portion.  A  loss  of  one  revolution  in  ten  at  once  reduces  the  pro- 
ductive power  of  every  machine  driven  by  the  engine  ten  per  cent, 
and  loses  to  the  proprietor  ten  per  cent  of  the  time  of  every 
workman  employed  to  manage  such  machine.  In  short,  the  loss 
of  one  revolution  in  ten  diminishes  the  productive  capacity  of  the 
whole  concern  ten  per  cent,  so  long  as  such  reduced  rate  con- 
tinues ;  while  the  expenses  of  conducting  the  shop  (rent,  wages, 
insurance,  etc.)  all  run  on  as  if  everything  was  in  full  motion. 
A  variation  to  this  amount  is  a  matter  of  frequent  occurrence, 
and  is,  indeed,  unavoidable,  unless  the  engineer  is  afforded 
facilities  to  prevent  it.  A  very  little  reflection  will  satisfy  any 
one  that  it  must  be  a  very  small  concern,  indeed,  in  which  a  half- 
hour's  continuance  of  it  would  not  produce  a  result  more  than 
enough  to  defray  the  cost  of  a  very  expensive  instrument  to  pre- 
vent it.  If  the  engineer,  to  avoid  this  loss,  keeps  a  surplus  of 
steam  constantly  on  hand,  he  is  constantly  wasting  the  steam, 
and  consequently,  fuel,  thus  incurring  another  loss,  which 
though  less  alarming  than  the  first  will  yet  be  serious  and  render 
any  instrument  most  desirable  which  can  prevent  it.  It  is,  there- 
fore, of  great  importance  to  the  proprietors  of  engines  to  have  an 
instrument  which  can  constantly  indicate  the  pressure  in  the 
steam  boilers  with  accuracy.  This  would  enable  the  engineer  to 
keep  his  steam  at  a  constant  pressure,  thus  avoiding  waste  of  fuel 
on  the  one  hand,  and  the  still  more  serious  loss  of  the  productive 
power  of  the  shop  on  the  other.  An  instrument,  therefore,  con- 
stantly indicating  the  pressure  of  steam,  reliable  in  its  character, 
and,  with  ordinary  care,  not  subject  to  derangement,  is  evidently 
a  desideratum  both  to  the  engineer  and  proprietor.  The  impor- 
tance of  such  an  instrument,  as  a  preventive  of  explosion,  and  of 
the  frightful  consequences  to  life  and  limb  and  ruinous  pecuniary 
results  of  such  disaster,  is  obvious  on  the  slightest  consideration ; 
but  the  value  of  the  instrument,  in  the  economical  results  of  its 
daily  use  is  by  no  means  properly  appreciated. 


HANDBOOK   ON   ENGINEERING.  491 

SAFETY-VALVES. 

The  form  and  construction  of  this  indispensable  adjunct  to  the 
steam  boiler  are  of  the  highest  importance,  not  only  for  the  pres- 
ervation of  life  and  property,  which  would,  in  the  absence  of  that 
means  of  "  safety"  be  constantly  jeopardized,  but  also  to  secure 
the  durability  of  the  steam  boiler  itself.  And  yet,  judging  from 
the  manner  in  which  many  things  called  safety-valves  have  been 
constructed  of  late  years,  it  would  appear  that  the  true  principle 
by  which  safety  is  sought  to  be  secured  by  this  most  valuable  ad- 
junct is  either  not  well  understood,  or  is  disregarded  by  many 
engineers  and  boiler  makers. 

Boiler  explosions  have  in  many  cases  occurred  when,  to  all 
appearances,  the  safety-valves  attached  have  been  in  good  work- 
ing order ;  and  coroners'  juries  have  not  unfrequently  been 
puzzled,  and  sometimes  guided  to  erroneous  verdicts  by  scientific 
evidence  adduced  before  them,  tending  to  show  that  nothing  was 
wrong  with  the  safety-valves,  and  that  the  devastating  catastro- 
phies  could  not  have  resulted  from  overpressure,  because  in  such 
case  the  safety-valve  would  have  prevented  them.  It  is  supposed 
that  a  gradually  increasing  pressure  can  never  take  place  if  the 
safety-valve  is  rightly  proportioned  and  in  good  working  order. 
Upon  this  assumption,  universally  acquiesced  in,  when  there  is  no 
accountable  cause,  explosions  are  attributed  to  the  u  sticking  " 
of  the  valves,  or  to  "bent"  valve-stems,  or  inoperative  valve- 
springs.  As  the  safety-valve  is  the  sole  reliance,  in  case  of  neg- 
lect or  inattention  on  the  part  of  the  engineer  or  fireman,  it  is 
important  to  examine  its  mode  of  working  closely.  Safety-valves 
are  usually  provided  with  a  spindle  or  guide-pin,  attached  to  the 
under  side,  and  passing  through  a  cross-bar  within  the  boiler, 
directly  under  the  seating  of  the  valve,  which  may  be  seen  in 


Figr,  263.    Lever  and  weight  safety-valve, 

corresponding  to  the  pressure  required  in  the  boiler.  Another 
difficulty  is  that  the  safety-valve  levers  sometimes  get  bent,  and 
the  weight,  consequently  hangs  on  one  side  of  the  true  center ; 
this,  it  will  be  seen,  causes  the  valve  to  rest  more  heavily  on  one 
side  than  on  the  other,  and  the  greater  the  added  weight  the 
greater  the  difficulty.  The  seats  of  safety-valves  should  be 
examined  frequently  to  see  that  no  corrosion  has  commenced  ;  as 
valves,  especially  if  leaky,  become  corroded  and  often  stick  fast, 
so  that  no  little  force  is  required  to  raise  them.  If,  when  a 
safety-valve  is  properly  weighted,  it  should  be  found  leaking,  do 
not  put  on  extra  weights,  but  immediately  make  an  examination, 
and  in  all  probability  the  seat  or  guide-pin  will  be  found  cor- 
roded, or  there  will  be  foreign  matter  between  the  valve  and  its 


HANDBOOK   ON   ENGINEERING.  493 

seat.  By  taking  the  lever  in  the  hand  and  raising  it  from  its  seat 
a  few  times,  any  substance  that  may  have  kept  it  from  its  seat 
will  be  dislodged ;  or  it  may  turn  out  on  examination  that  the 
lever  had  deviated  from  some  cause  from  a  true  center.  Such 
difficulties  can  be  easily  righted,  but  extra  weight  should  never  be 
added,  as  it  only  aggrevates  the  trouble  instead  of  remedying  it. 
When  the  weight  of  the  safety-valve  is  set  on  the  lever  at  safe 
working  pressure,  or  at  the  distance  from  the  fulcrum  necessary 
to  maintain  the  pressure  required  to  work  the  engine,  any 
extra  length  of  lever  should  then  be  cut  off  as  a  precaution, 
to  prevenf  the  moving  out  of  the  weight  on  the  lever,  for  the 
purpose  of  increasing  the  pressure,  as,  while  the  lever  remains 
sufficiently  long,  the  weight  can  be  increased  to  a  dangerous 
extent  without  attracting  any  attention  ;  while  if  the  lever  is  cut 
off  at  the  point  at  which  the  safe  working  pressure  is  designated, 
any  extra  increase  of  pressure  can  only  be  accomplished  by  add- 
ing more  weight  to  the  lever,  which  is  tolerably  sure  to  attract  the 
attention  of  some  one  interested  in  the  preservation  of  the  lives 
and  property  of  persons  in  the  immediate  vicinity. 

The  bolts  that  form  the  connection  between  the  lever,  fulcrum 
and  valve-stem  should  be  made  of  brass,  in  order  to  prevent  the 
possibility  of  corrosion,  "sticking  "  or  becoming  magnetized,  as 
it  is  termed  ;  and  for  the  same  reason,  the  valve  and  seat  should 
be  made  of  two  different  metals.  When  safety-valves  become 
leaky  they  should  be  taken  out  and  reground  on  their  seats,  for 
which  purpose  pulverized  glass,  flour  of  emery,  or  the  fine  grit  or 
mud  from  grinding  stone  troughs  are  the  most  suitable  material ; 
but  whether  they  leak  or  not,  they  should  be  taken  apart  at  least 
once  a  year  and  all  the  working  parts  cleaned,  oiled  and  read- 
justed. The  safety-valve  is  designed  on  the  assumption  that  it 
will  rise  from  its  seat  under  the  statical  pressure  in  the  boiler 
when  this  pressure  exceeds  the  exterior  pressure  on  the  valve,  and 
that  it  Will  remain  off  its  seat  sufficiently  far  to  permit  all  the 


494  HANDBOOK  ON    ENGINEERING. 

steam  which  the  boiler  can  produce  to  escape  around  the  edges  of 
the  valve.  The  problem  then  to  be  solved  is :  What  amount  of 
opening  is  necessary  for  the  free  escape  of  the  steam  from  the 
boiler  under  a  given  pressure?  The  area  of  a  safety-valve 
is  generally  determined  from  formulae  based  on  the  velocity 
of  the  flow  of  steam  under  differet  pressures,  or  upon  the 
results  of  experiments  made  to  ascertain  the  area  necessary  for 
the  escape  of  all  the  steam  a  boiler  could  produce  under  a  given 
pressure.  But  as  the  fact  is  now  generally  recognized  by 
engineers  that  valves  do  not  rise  appreciably  from  their  seats 
under  varying  pressures,  it  is  of  importance  that  in  practice 
the  outlets  round  their  edges  should  be  greater  than  those  based 
on  theoretical  considerations.  The  next  point  to  be  considered  is 
how  high  any  safety  valve  will  rise  under  the  influeuce  of  a  given 
pressure!  This  question  cannot  be  determined  theoretically,  but 
has  been  settled  conclusively  by  Burg,  of  Vienna,  who  made 
careful  experiments  to  determine  the  actual  rise  of  safety-valves 
above  their  seats.  His  experiments  show  that  the  rise  of  the 
valve  diminishes  rapidly  as  the  pressure  increases. 

' 

TABLE     SHOWING     THE     RISE     OF     SAFETY-VALVES,     IN    PARTS    OF    AN 
INCH,  AT  DIFFERENT  PRESSURES. 


Lbs,  Lbs.  Lbs.  Lbs.  Lbs.  Lbs.  Lbs.  Lbs.  Lbs. 


12  20  35  45   50  60   70   80   90 
-ffV  sV  iV  li?  ifa  yis 


4*8  A  - 


Taking  ordinary  safety-valves,  the  average  rise  for  pressures 
from  10  to  40  pounds  is  about  ^  of  an  inch  from  40  to  70 
pounds  about  ¥L,  and  from  70  to  90  pounds  about  ^^  of  an 
inch.  The  following  table  gives  the  re'sult  of  a  series  of  experi- 
ments made  at  the  Novelty  Iron  Works,  New  York,  for  the  pur- 
pose of  determining  the  exact  area  of  opening  necessary  for 


HANDBOOK    ON    ENGINEERING. 


495 


safety-valves  for  each  square  foot  of  heating  surface,  at  different 
boiler  pressures. 


TABLE. 


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200 

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.009259 

TABLE   OF   COMPARISON  BETWEEN  EXPERIMENTAL   RESULTS  AND 
THEORETICAL  FORMULAE. 


Boiler  Pressure,  45  pounds. 


Boiler  Pressure,  75  pounds. 


Heating 
Surface. 

Area  of  open- 
ing found  by 
experiment. 

Area  of  open- 
ing according 
to  formulae. 

Heating 
Surface. 

Area  of  open- 
ing fonnd  by 
experiment.. 

Area  of  open- 
ing according 
to  formulae. 

Sq.  Ft. 

Sq.  Ins. 

Sq.  Ins. 

Sq.  Ft. 

Sq.  Ins. 

Sq.  Ins. 

100 

.  .089 

.09 

100 

.12 

.12 

200 

.180 

.19 

200 

.24 

.24 

500 

.45 

.48 

500 

.59 

.59 

1000 

.89 

.94 

1000 

1.20 

1.18 

2000 

1.78 

1.90 

2000 

2.40 

2.37 

5000 

4.46 

4.75 

5000 

6.00 

6.95 

496  HANDBOOK   ON   ENGINEERING. 

Now,  if  we  compare  the  area  of  openings,  according  to  these 
experiments,  with  Zeuner's  formula  which  is  entirely  theoretical, 
it  will  be  observed  that  the  results  from  the  two  sources  are 
almost  identical,  or  so  nearly  so  as  not  to  make  any  material 
difference.  In  the  absence  of  any  generally  recognized  rule,  it 
is  customary  for  engineers  and  boiler-makers  to  proportion  safety- 
valves  according  to  the  heating  surface,  grate  surface,  or  horse- 
power of  the  boiler.  While  one  allows  one  inch  of  area  of 
safety-valve  to  66  square}  feet  of  heating  surface,  another  gives 
one-inch  area  of  safety-valve  to  every  four-horse  power ;  while  a 
third  proportion's  his  by  the  grate  surface  —  it  being  the  custom 
in  such  cases  to  allow  one  inch  of  safety-valves  to  2  square 
feet  of  grate  surface.  This  latter  proportion  has  been  proved  by 
long  experience  and  a  great  number  of  accurate  experiments  to, 
be  capable  of  admitting  of  a  free  escape  of  steam  without  allowing 
any  material  increase  of  the  pressure  beyond  that  for  which  the 
valve  is  loaded,  even  when  the  fuel  is  of  the  best  quality,  and  the 
consumption  as  high  as  24  pounds  of  coal  per  hour  per  square 
foot  of  grate  surface,  providing  of  course  that  all  the  parts  are 
in  good  working  order.  It  is  obvious,  however,  that  no  valve 
can  act  without  a  slight  increase  of  pressure,  as,  in  order  to  lift 
at  all,  the  internal  pressure  must  exceed  the  pressure  due  to  the 
load. 

The  lift  of  safety-valves,  like  all  other  puppet  valves,  de- 
creases as  the  pressure  increases,  but  this  seeming  irregularity  is 
but  what  might  be  required  of  an  orifice  to  satisfy  conditions  in 
the  flow  of  fluids,  and  may  be  explained  as  follows :  A  cubic  foot 
of  water  generated  into  steam  at  one-pound  pressure  per  square 
inch  above  the  atmosphere,  will  have  a  volume  of  about  1,600 
cubic  feet.  Steam  at  this  pressure  will  flow  into  the  atmosphere 
with  a  velocity  of  482  feet  per  second.  Now  suppose  the  steam 
was  generated  in  five  minutes,  or  in  300  seconds,  and  the  area  of 
an  orifice  to  permit  its  escape  as  fast  it  is  generated  be  re- 


HANDBOOK   ON   ENGINEERING.  497 

quired,  1600  x  144  -*-  (482  x  300)  will  give  the  area  of  the  orifice, 
1|  square  inches.  If  the  same  quantity  of  water  be  generated  into 
steam  at  a  pressure  of  50  pounds  above  the  atmosphere,  it  will 
possess  a  volume  of  440  cubic  feet  and  will  flow  into  the  atmos- 
phere with  a  velocity  of  1791  feet  per  second.  The  area  of  an 
orifice,  to  allow  this  steam  to  escape  in  the  same  time  as  in  the 
first  case,  may  be  found  as  follows:  440  x  144  -r-  (1791  x  300), 
the  result  will  be  ^  square  inches,  or  nearly  £  of  a  square  inch,  the 
area  required.  It  is  evident  from  this  that  a  much  less  lift  of  the 
same  valve  will  suffice  to  discharge  the  same  weight  of  steam 
under  a  high  pressure  than  under  a  low  one,  because  the  steam 
under  a  high  pressure  not  only  possesses  a  reduced  volume,  but  a 
greatly  increased  velocity ;  it  is  also  obvious  from  these  consider- 
ations, that  a  safety-valve,  to  discharge  steam  as  fast  as  the  boiler 
can  generate  it,  should  be  pioportioned  for  the  lowest  pressure. 

RULES. 

Rule,  —  For  finding  the  weight  necessary  to  put  on  a  safety- 
valve  lever  when  the  area  of  valve,  pressure,  etc.,  are  known: 
Multiply  the  area  of  valve  by  the  pressure  in  pounds  per  square 
inch ;  multiply  this  product  by  the  distance  of  the  valve  from  the 
fulcrum ;  multiply  the  weight  of  the  lever  by  one-half  its  length 
(or  its  center  of  gravity)  ;  then  multiply  the  weight  of  valve  and 
stem  by  their  distance  from  the  fulcrum  ;  add  these  last  two  prod- 
ucts together,  subtract  their  sum  from  the  first  product,  and 
divide  the  remainder  by  the  length  of  the  lever ;  the  quotient  will 
be  the  weight  required. 

EXAMPLE. 

Area  of  valve,  12  in 65          13         8 

Pressure,  65  Ibs. 12         16         4 

Fulcrum,  4  in.  . 780       208       62 

82 


498  HANDBOOK    ON    ENGINEERING. 

Length  of  lever,  32  in 4         13 

Weight  of  lever,  13  Ibs 

Weight  of  valve  and  stem,  8  Ibs.     .     .     .     .     3120       208 

240         32 

32)2880       240 
90  Ibs. 

Rule  for  finding  the  pressure  per  square  inch  when  the  area  of 
ralve,  weight  of  ball,  etc.,  are  known:  Multiply  the  weight  of  ball 
by  length  of  lever,  and  multiply  the  weight  of  lever  by  one-half  its 
length  (or  its  center  of  gravity)  ;  then  multiply  the  weight  of 
valve  and  stem  by  their  distance  from  the  fulcrum.  Add  these 
three  products  together.  This  sum,  divided  by  the  product  of 
the  area  of  valve,  and  its  distance  from  the  fulcrum,  will  give  the 
pressure  in  pounds  per  square  inch. 

EXAMPLE. 

Area  of  valve,  7  in 50         12         6 

Fulcrum,  3  in 30         15         3 

Length  of  lever,  30  in 1500        180       18 

Weight  of  lever,  12  Ibs 180 


Weight  of  ball,  50  Ibs 18  7 

Weight  of  valve  and  stem,  6  Ibs 

21)1698  3 

80.85  Ibs.       21 

Rule  for  finding  the  pressure  at  which  a  safety-valve  is 
weighted  when  the  length  of  the  lever,  weight  of  ball,  etc.,  are 
known :  Multiply  the  length  of  lever  in  inches  by  the  weight  of 
ball  in  pounds ;  then  multiply  the  area  of  valve  by  its  distance 


HANDBOOK    ON    ENGINEERING.  499 

from  the  fulcrum ;  divide  the  former  product  by  the  latter ;  the 
quotient  will  be  the  pressure  in  pounds  per  square  inch. 

EXAMPLE. 

Length  of  lever,  24  in 52  7 

Weight  of  ball,  52  Ibs 24  3 

Fulcrum,  3  in.     .     . 208         21 

Area  of  valve,  7  in 104 


21)1248 

59. 42  Ibs. 

The  above  rule,  though  very  simple,  cannot  be  said  to  be 
exactly  correct,  as  it  does  not  take  into  account  the  weight  of  the 
lever,  valve  and  stem. 

Rule  for  finding  center  of  gravity  of  taper  levers  for  safety- 
valves  :  Divide  the  length  of  lever  by  two  (2)  ;  then  divide 
the  length  of  lever  by  six  (6),  and  multiply  the  latter  quotient 
by  width  of  large  end  of  lever  less  the  width  of  small  end, 
divided  by  width  of  large  end  of  lever  plus  the  width  of  small  end. 
Subtract  this  product  from  the  first  quotient,  and  the  remainder 
will  be  the  distance  in  inches  of  the  center  of  gravity  from  large 
end  jf  lever. 

EXAMPLE. 

Length  of  lever 36  in. 

Width  of  lever  at  large  end 3   c 

Width  of  lever  at  small  end 2   ' 

36  divided  by  2  =  18  minus  1,2  =  36.8  in.     36  divided  by  6  = 
6X1=6  divided  by  5  =  1.2. 

Center  of  gravity  from  large  end,  16.8  in. 

The  safety-valve  has  not  received  that  attention  from  engi- 
neers and  inventors  which  its  importance  as  a  means  of  safety 


500  HANDBOOK    ON    ENGINEERING. 

so  imperatively  deserves.  In  the  construction  of  most  other 
kinds  of  machinery,  continual  efforts  have  been  made  to  secure 
and  insure  accuracy ;  while  in  the  case  of  the  safety-valve,  very 
little  improvement  has  been  made  either  in  design  or  fitting.  It 
is  difficult  to  see  why  this  should  be  so,  when  it  is  known  that 
deviations  from  exactness,  though  trifling  in  themselves,  when 
multiplied,  not  only  affect  the  free  action  and  reliability  of 
machines,  but  frequently  result  in  serious  injury,  more  partic- 
ularly in  the  case  of  safety-valves. 

Safety-valves  should  never  be  made  with  rigid  stems,  as,  in 
consequence  of  the  frequent  inaccuracy  of  the  other  parts,  the 
valve  is  prevented  from  seating,  thereby  causing  leakage ;  as  a 
remedy  for  which,  through  ignorance  or  want  of  skill,  more 
weight  is  added  on  the  lever,  which  has  a  tendency  to  bend 
the  stem,  thus  rendering  the  valve  a  source  of  danger  instead 
of  a  means  of  safety.  The  stem  should,  in  all  cases,  be  fitted 
to  the  valve  with  a  ball  and  socket  joint,  or  a  tapering  stem 
in  a  straight  hole,  which  will  admit  of  sufficient  vibration  to 
accommodate  the  valve  to  its  seat.  It  is  also  advisable  that 
the  seats  of  safety-valves,  or  the  parts  that  bear,  should  be  as 
narrow  as  circumstances  will  permit,  as  the  narrower  the  seat 
the  less  liable  the  valve  is  to  leak,  and  the  easier  it  is  to  repair 
when  it  becomes  leaky. 

All  compound  or  complicated  safety-valves  should  be  avoided, 
as  a  safety-valve  is,  in  a  certain  sense,  like  a  clock — any 
complication  of  its  parts  has  a  tendency  to  affect  its  reliability 
and  impair  its  accuracy. 

It  has  been  too  much  the  custom  heretofore  for  owners  of  steam 
boilers  to  disregard  the  advice  and  suggestions  of  their  own  en- 
gineers and  firemen,  even  though  men  of  intelligence  and  experi- 
ence, and  to  be  governed  entirely  by  the  advice  of  self-styled 
experts  and  visionary  theorists. 


HANDBOOK   ON   ENGINEERING. 


501 


TABLE    OF    HEATING   SURFACE    IX   SQUARE   FEET    IN   HORI- 
ZONTAL TUBULAR  BOILERS. 


Diam.  of  Boiler  in  inches 

24 

30 

32 

34 

36 

38 

40 

*2 

44 

48 

f  Heating  surface  of  shell 
per  foot  of  length. 

4.19 

5.24 

5.57 

5.93 

6.28 

6.63 

6.98 

7.73 

7.68 

8.38 

Diameter  of  Tube  or  Flue 
in  inches. 

2 

24 

3 

34 

4 

44 

5 

6 

7 

8 

Whole   External  Heating 
surface  per  foot  length. 

.524 

.655 

.785 

.916 

1.05 

1.18 

1.31 

1.57 

1.83 

2.09 

60 

52 

54 

56 

58 

60 

62 

64 

66 

68 

70 

72 

8.73 

9.08 

9.42 

9.77 

10.12 

10.47 

10.82 

11.17 

11.52 

11.87 

12.22 

12.57 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

2.36 

2.62 

2.88 

3.14 

3.40 

3.66 

3.93 

4.19 

4.45 

4.71 

4.96 

5.24 

CENTRIFUGAL  FORCE. 

The  centrifugal  force  of  a  body  depends  upon  its  weight  Win 
pounds ;  distance  R  in  feet  it  is  from  the  center  of  rotation,  and 
the  number  of  revolutions  N  it  makes  about  that  center  each 

WEN* 
minute  and  equals  — 9933 — * 

Multiply  the  weight  in  pounds  by  radius  in  feet,  by  square 
of  number  of  revolutions,  and  divide  by  2933  =  centrifugal  force 
in  pounds. 


502  HANDBOOK    ON    ENGINEERING. 

CHAPTER     XVIII. 
THE  WATER  TUBE  BOILER. 

The  water  tube  boiler  has  been  a  growth  of  many  years 
and  of  many  different  minds.  There  are  some  two  and  a 
half  million  horse-power  in  daily  service  in  the  United  States 
alone,  and  the  number  is  rapidly  increasing.  Large  orders  for 
this  type  of  boiler  have  often  been  repeated,  adding  proof  that  its 
principles  are  correct  and  appreciated  by  those  having  them  in 
use  and  in  charge.  This  being  the  case,  purchasers  should  note 
well  the  points  of  difference  in  the  various  water  tube  boilers 
claiming  their  attention,  and  particularly  see  that  the  claims 
made  for  them  are  embodied  in  their  actual  construction.  The 
general  principles  of  construction  and  operation  of  this  class  of 
steam  boilers  are  now  well  known  to  engineers  and  steam  users. 
In  selecting  a  water  tube  boiler  there  are  several  vital  points  to 
be  considered :  — 

1st.  Straight  and  smooth  passages  through  the  headers  of  ample 
area,  insuring  rapid  and  uninterrupted  circulation  of  the  water. 

2d.  The  baffling  of  the  gases  (without  throttling  or  impeding 
the  circulation  of  the  water)  in  such  a  way  that  they  are  com- 
pelled to  pass  over  every  portion  of  the  heating  surface. 

3d.  Sufficient  liberating  surface  in  the  steam  drums  to 
insure  dry  steam,  with  large  body  of  water  in  reserve  to  draw 
from. 

4th.  A  steam  reservoir  or  steam  drum. 

5th.  Simplicity  in  construction ;  accessibility  for  cleaning  and 
inspection. 

6th.  A  header,  which  in  its  design  provides  for  the  unequal 
expansion  and  contraction. 


HANDBOOK    ON    ENGINEERING. 


503 


Fig.  264.    O'Brien  horizontal  safety  water   tube  boiler. 

Manufactured    by    the    John    O'Brien    Boiler  Works    Company, 

of  St.  Louis,  U.  8.  A. 
This  type  of  water  tube  boiler  when  provided  with  a  cross-drum 

to  reduce  the  head  room  required  is  adapted  to,  and  is  oftentimes 
used  in  heating  plants. 

Down  draft  furnace*  —  A  great  many  of  these  boilers  are  fit- 
ted with  the  down  draft  furnaces,  and  the  above  illustration  shows 
the  style  of  same,  together  with  the  manner  in  which  they  are 
connected. 

A  full  and  complete  description  of  these  furnaces  is  given  on 
page  522. 

Description*  —  In    construction,  this   type  of   boiler  consists 


504  HANDBOOK    ON    ENGINEERING. 

simply  of  a  front  and  rear  water  leg  or  header,  made  approx- 
imately rectangular  in  shape,  overhead  combination  steam  and 
water  drum  or  drums  and  with  circulating  water  tubes,  as 
shown  in  cut,  which  extend  between  and  connect  both  front  and 
rear  headers,  being  thoroughly  expanded  into  the  tube  sheets. 
The  tubes  are  inclined  on  a  pitch  of  one  inch  to  the  foot  and  the 
rear  header  being  longer  than  the  front  one,  the  overhead  drum 
connecting  both  headers  lies  perfectly  level  when  the  boiler  is  set 
in  position.  The  connection  of  the  headers  with  the  combined 
steam  and  water  drum  is  made  in  such  a  manner  as  to  give  prac- 
tically the  same  area  as  the  total  area  of  the  tubes,  so  there  is  no' 
contraction  of  area  in  the  course  of  circulation ;  and  extending 
between  and  connecting  the  inside  faces  of  the  water  legs, 
which  form  end  connections  between  these  tubes  and  the  com- 
bined steam  and  water  drums  or  shells,  placed  above  and  parallel 
with  them,  also  a  steam  drum  above  these,  assures  absolutely  dry 
steam  and  a  large  steam  space,  also  a  large  water  space.  The  water 
legs  are  made  larger  at  the  top,  about  11  inches  wide,  and  at  the 
bottom  about  7  inches  wide,  which  is  a  great  advantage,  allowing 
the  globules  of  steam  to  pass  quickly  up  the  water  legs  to  the 
steam  and  water  drums.  The  water,  as  it  sweeps  along  the 
drums,  frees  itself  of  steam  ;  then  it  goes  down  the  back  connec- 
tion until  it  meets  the  inclined  tubes,  meeting  on  its  passage  a 
gradually  increasing  temperature,  till  the  furnace  is  again  reached, 
where  the  steam  formed  on  the  way  is  directly  carried  up  in  the 
drum  as  before.  The  tubes  extend  between  and  connect  both  the 
front  and  rear  headers  and  are  thoroughly  expanded  into  the 
tube  sheets.  Opposite  the  end  of  each  tube  there  is  an  oval 
hand-hole  slightly  larger  than  the  tube  proper  through  which  it 
can  be  withdrawn.  It  will  be  noted  that  the  throat  of  each 
water  leg  is  1^  times  the  total  tube  area.  The  rapid  and 
unimpeded  circulation  tends  to  keep  the  inside  surface  clean  and 
floats  the  scale-making  sediment  along  until  it  reaches  the  back 


HANDBOOK   ON    ENGINEERING. 


505 


water  leg,  where  it  is  carried  down  and  settles  in  the  bottom  of  leg, 
where  it  is  blown  off  at  regular  intervals. 


Fte.  265.    Formation  of  front  water  leg  in  O'Brien  boiler. 
Steadiness  of  wate*  level  —  The  large  area  of  surface  at  watei 
line  and  the  ample  passages  for  circulation,  secure  a  steadiness 


506  HANDBOOK    ON    ENGINEERING. 

of  water  level  peculiar  to  this  type.  This  is  a  most  im- 
portant point  in  boiler  construction  and  should  always  be  consid- 
ered when  comparing  boilers.  The  water  legs  are  stayed  by  hol- 
low stay-bolts  of  hydraulic  tubing  of  large  diameter,  so  placed  that 
two  stays  support  each  tube  and  hand-hole  and  are  subjected  to  only 
very  slight  strain.  Being  made  of  heavy  material,  they  form  the 
strongest  parts  of  the  boiler  and  its  natural  supports.  The  water 
legs  are  joined  to  the  shell  by  flanged  and  riveted  joints  and  the 
drum  is  cut  away  at  these  two  points  to  make  connection  with  in- 
side of  water  leg,  the  opening  thus  made  being  strengthened  by 
special  stays,  so  as  to  preserve  the  original  strength.  The  shells 
are  cylinders  with  heads  dished  to  form  part  of  a  true  sphere. 
The  sphere  is  everywhere  as  strong  as  the  circular  seam  of  the 
cylinder,  which  is  well  known  to  be  twice  as  strong  as  the  side 
seam ;  therefore,  the  heads  require  no  stays.  Both  the  cylinder 
and  the  spherical  heads  are,  therefore,  free  to  follow  their  natural 
lines  of  expansion  when  put  under  pressure. 

The  illustration  on  page  505  plainly  shows  the  formation  of 
the  front  water  leg  or  header  in  this  type  of  water  tube  boiler. 

It  will  be  seen  that  the  hand  plates  are  all  oval  in  shape,  a] low- 
ing each  one  to  be  removed  from  its  respective  hole ;  also,  the 
manner  of  bracing  with  hollow  stay-bolts  is  shown. 

Note  that  the  feed  pipes  for  supplying  boiler  run  back  to  rear 
water  leg  and  discharge  therein. 

Walling'  in*  —  In  setting  the  boiler,  its  front  water  leg  is  placed 
firmly  on  a  set  of  strong,  cast-iron  columns  bolted  and  braced  to- 
gether by  the  door  frames  and  dead-plates  and  forming  the  fire 
front.  This  is  the  fixed  end.  The  rear  water  legs  rest  on  rollers 
which  are  free  to  move  on  cast-iron  plates  firmly  set  in  the  ma- 
sonry of  the  low  and  solid  rear  wall.  Thus  the  boiler  and  its  walls 
are  each  free  to  move  separately  during  expansion  or  contraction, 
without  loosening  any  joints  in  the  masonry. 

On  the  lower,  and  between  the  upper  tubes,   are  placed  light 


HANDBOOK    ON   ENGINEERING.  507 

fire-brick  tiles.  The  lower  tier  extends  from  the  front  water  leg 
to  within  a  few  feet  of  the  rear  one,  leaving  there  an  upward  pass- 
age across  the  rear  ends  of  the  tubes  for  the  flame.  The  upper 
tier  closes  into  the  rear  water  leg  and  extends  forward  to  within 
a  few  feet  of  the  front  one,  thus  leaving  an  opening  for  the  gases 
in  front.  The  side  tiles  extend  from  side  walls  to  tile  bars  and 
close  up  to  the  front  water  leg  and  front  wall,  and  leave  open  the 
final  uptake  for  the  waste  gases. 

The  gases  being  thoroughly  mingled  in  their  passage  between 
the  staggered  tubes,  the  combustion  is  more  complete,  and  the 
gases  impinging  against  the  heating  surface  perpendicularly,  in- 
stead of  gliding  along  the  same  longitudinally,  the  absorption  of 
the  gas  is  more  thorough.  The  draft  area,  being  much 
larger  than  in  fire  tube  boilers,  gives  ample  time  for  the 
absorption  of  the  heat  of  the  gases  before  their  exit  to  the 
chimney. 

DESCRIPTION  OF  THE  HEINE  SAFETY  BOILER. 

The  boiler  is  composed  of  lap- welded  wrought-iron  tubes  ex- 
tending between  and  connecting  the  inside  faces  of  two  "  water 
legs,"  which  form  the  end  connections  between  these  tubes  and 
a  combined  .steam  and  water  drum  or  "  shell  "  placed  above  and 
parallel  with  them.  Boilers  over  200  horse-power  have  two  such 
shells.  These  end  chambers  are  of  approximately  rectangular 
shape,  drawn  in  at  top  to  fit  the  curvature  of  the  shells.  Each  is 
composed  of  a  head  plate  and  a  tube  sheet  flanged  all  around 
and  joined  at  bottom  and  sides  by  a  butt  strap  of  same  material, 
strongly  riveted  to  both.  The  water  legs  are  further  stayed  by 
hollow  stay-bolts  of  hydraulic  tubing  of  large  diameter,  so  placed 
that  two  stays  support  each  tube  and  hand-hole  and  are  subjected 
to  only  very  slight  strain.  Being  made  of  heavy  metal,  they  form 
the  strongest  parts  of  the  boiler  and  its  natural  supports.  The 


508  HANDBOOK    ON   ENGINEERING. 

water  le-s  are  joined  to  the  shell  by  flanged  and  riveted  joints, 
the  drum  i  cut  away  at  these  two  points  to  make  connects 


with  inside  of  water  leg,  the  opening  thus   made  being  strength- 
ened by  bridges  and  special  stays  so  as  to  preserve  1 

strength. 

48 


HANDBOOK    ON    ENGINEERING.  509 

The  shells  are  cylinders  with  heads  dished  to  form  parts  of  a 
true  sphere.  The  sphere  is  everywhere  as  strong  as  the  circle 
seam  of  the  cylinder,  which  is  well  known  to  be  twice  as  strong  as 
its  side  seam.  Therefore,  these  heads  require  no  stays.  Both 
the  cylinder  and  its  spherical  heads  are,  therefore,  free  to  follow 
their  natural  lines  of  expansion  when  put  under  pressure.  Where 
flat  heads  have  to  be  braced  to  the  sides  of  the  shell,  both  suffer 
local  distortions  where  the  feet  of  the  braces  are  riveted  to  them, 
making  the  calculations  of  their  strength  fallacious.  This  they 
avoid  entirely  by  their  dished  heads.  To  the  bottom  of  the  front 
head  a  flange  is  riveted,  into  which  the  feed-pipe  is  screwed. 
This  pipe  is  shown  in  the  cut  with  angle  valve  and  check  valve 
attached.  On  top  of  shell,  near  the  front  end,  is  riveted  a  steam 
nozzle  or  saddle,  to  which  is  bolted  a  tee.  This  tee  carries  the  steam 
valve  on  its  branch,  which  is  made  to  look  either  to  front,  rear, 
right  or  left ;  on  its  top  the  safety  valve  is  placed.  The  saddle 
has  an  area  equal  to  that  of  stop  valve  and  safety  valve  combined. 
The  rear  head  carries  a  blow-off  flange  of  about  same  size  as  the 
feed  flange,  and  a  manhead  curved  to  fit  the  head,  the  manhole 
supported  by  a  strengthening  ring  outside.  On  each  side  of  the 
shell  a  square  bar,  the  tile-bar,  rests  loosely  in  flat  hooks  riveted 
to  the  shell..  This  bar  supports  the  side  tiles,  whose  other  ends 
rest  on  the  side  walls,  thus  closing  the  furnace  or  flue  on  top. 
The  top  of  the  tile-bar  is  two  inches  below  low  water  line.  The 
bars  rise  from  front  to  rear  at  the  rate  of  one  inch  in  twelve. 
When  the  boiler  is  set,  they  must  be  exactly  level,  the  whole 
boiler  being  then  on  an  incline,  i.  e.,  with  a  fall  of  one  inch  in 
twelve  from  front  to  rear.  It  will  be  noted  that  this  makes  the 
height  of  the  steam  space  in  front  about  two-thirds  the  diam- 
eter of  the  shell,  while  at  the  rear  the  water  occupies  two-thirds 
of  the  shell,  the  whole  contents  of  the  drum  being  equally  divided 
between  steam  and  water.  The  importance  of  this  will  be  ex- 
plained hereafter. 


510 


HANDBOOK   ON   ENGINEERING. 


The  tubes  extend  through  the  tube  sheets,  into  which  they  are 
expanded  with  roller  expanders  ;  opposite  the  end  of  each  and  in 
the  head  plates,  is  placed  a  hand-hole  of  slightly  larger  diam- 


. 


Fig.  267.    Details  of  construction  —  Heine  boiler. 

eter  than  the  tube,  and  through  which  it  can  be  withdrawn. 
These  hand-holes  are  closed  by  small  cast-iron  hand-hole  plates, 
,  by  an  ingenious  device  for  locking,  can  be  removed  in  a 


HANDBOOK  .ON    ENGINEERING.  511 

few  seconds  to  inspect  or  clean  a  tube.  The  accompanying  cut 
shows  these  hand-hole  plates  marked  H.  In  the  upper  corner 
one  is  shown  in  detail,  H2  being  the  top  view,  H*  the  side  view 
of  the  plate  itself,  the  shoulder  showing  the  place  for  the  gasket. 
Hl  is  the  yoke  or  crab  placed  outside  to  support  the  bolt  and  nut. 
Inside  of  the  shell  is  located  the  mud  drum  D,  placed  well 
below  the  water  line,  usually  parallel  to  and  3  inches  above  the 
bottom  of  the  shell.  It  is  thus  completely  immersed  in  the  hot- 
test water  in  the  boiler.  It  is  of  oval  section,  slightly  smaller 
than  the  manhole,  made  of  strong  sheet-iron  with  cast-iron  heads. 
It  is  entirely  inclosed  except  about  18  inches  of  its  upper 
portion  at  the  forward  end,  which  is  cut  away  nearly  parallel  to 
the  water  line.  Its  action  will  be  explained  below.  The  feed- 
pipe F  enters  it  through  a  loose  joint  in  front ;  the  blow-off  pipe 
N  is  screwed  tightly  into  its  rear-head,  and  passes  by  a  steam- 
tight  joint  through  the  rear-head  of  the  shell.  Just  under  the 
steam  nozzle  is  placed  a  dry  pan  or  dry  pipe  A.  A  deflection 
plate  L  extends  from  the  front  head  of  the  shell,  inclined  up- 
wards, to  some  distance  beyond  the  mouth  or  throat  of  the  front 
water  leg.  It  will  be  noted  that  the  throat  of  each  water  leg  is 
large  enough  to  be  the  practical  equivalent  of  the  total  tube  area, 
and  that  just  where  it  joins  the  shell  it  increases  gradually  in 
width  by  double  the  radius  of  the  flange. 

Erection  and  walling  in*  —  In  setting  the  boiler,  its  front 
water  leg  is  placed  firmly  on  a  set  of  strong  cast-iron  columns, 
bolted  and  braced  together  by  the  door  frames,  deadplate,  etc., 
and  forming  the  fire  front.  This  is  the  fixed  end.  The  rear 
water  leg  rests  on  rollers,  which  are  free  to  move  on  cast-iron 
plates  firmly  set  in  the  masonry  of  the  low  and  solid  rear  wall. 
Wherever  the  brickwork  closes  in  to  the  boiler,  broad  joints  are 
left  which  are  filled  in  with  tow  or  waste  saturated  with  fireclay, 
or  other  refractory  but  pliable  material.  Thus  the  boiler  and  its 
walls  are  each  free  to  move  separately  during  expansion  or  con- 


512  HANDBOOK    ON    ENGINEERING. 

traction  without  loosening  any  joints  in  the  masonry.  On  the 
lower,  and  between  the  upper  tubes,  are  placed  light  firebrick 
tiles.  The  lower  tier  extends  from  the  front  water  leg  to  within 
a  few  feet  of  the  rear  one,  leaving  there  an  upward  passage  across 
the  rear  ends  of  the  tubes  for  the  flame,  etc.  The  upper  tier 
closes  in  to  the  rear  water  leg  and  extends  forward  to  within  a 
few  feet  of  the  front  one,  thus  leaving  the  opening  for  the  gases  in 
front.  The  side  tiles  extend  from  side  walls  to  tile  bars  and  close 
up  to  the  front  water  leg  and  front  wall,  and  leave  open  the  final 
uptake  for  the  waste  gases  over  the  back  part  of  the  shell,  which 
is  here  covered  above  water  line  with  a  rowlock  of  firebrick  rest- 
ing on  the  tile  bars.  The  rear  wall  of  the  setting  and  one  paral- 
lel to  it  arched  over  the  shell  a  few  feet  forward,  form  the  uptakes. 
On  these  and  the  rear  portion  of  the  side  walls  is  placed  a  light 
sheet-iron  hood,  from  which  the  breeching  leads  to  the  chimney. 
When  an  iron  stack  is  used,  this  hood  is  stiffened  by  L  and  T 
irons  so  that  it  becomes  a  truss  carrying  the  weight  of  such  stack 
and  distributing  it  to  the  side  walls. 

Heine  boiler  and  its  operation*  —  The  boiler  being  filled 
to  middle  water  line,  the  fire  is  started  on  the  grate.  The 
flame  and  gases  pass  over  the  bridge  wall  and  under  the 
lower  tier  of  tiling,  finding  in  the  ample  combustion  chamber 
space,  temperature  and  air  supply  for  complete  combustion, 
before  bringing  the  heat  in  contact  with  the  main  body  of  the 
tubes.  Then,  when  at  its  best,  it  rises  through  the  spaces  be- 
tween the  rear  ends  of  the  tubes,  between  rear  water  leg  and  back 
end  of  the  tiling,  and  is  allowed  to  expand  itself  on  the  entire 
tube  heading  surface  without  meeting  any  obstruction.  Ample 
space  makes  leisurely  progress  for  the  flames,  which  meet  in  turn 
all  the  tubes,  lap  round  them,  and  finally  reach  the  second  uptake 
at  the  forward  end  of  the  top  tier  of  tiling,  with  their  temperature 
reduced  to  less  than  900°  Fahrenheit.  This  has  been  measured 
here,  while  wrought  iron  would  melt  just  above  the  lower.tubes  at 


HANDBOOK    ON    ENGINEERING. 


513 


rear  end.  showing  a  reduction  of  temperature  of  over  1,800°  Fahr. 
between  the  two  points.  As  the  space  is  studded  with  water 
tubes,  swept  clean  by  a  positive  and  rapid  circulation,  the  absorp- 
tion of  this  great  amount  of  heat  is  explained.  The  gases  next 
travel  under  the  bottom  and  sides  of  shell  and  reach  the  uptake 
at  just  the  proper  temperature  to  produce  the  draft  required. 
This  varies,  of  course,  according  to  chimney,  fuel  required,  etc. 
With  boilers  running  at  their  rated  capacity,  450°  Fahrenheit  are 


Fig.  2<»8.     A  furnace  that  is  used  in  the  Eust. 

seldom  exceeded.  Meanwhile,  as  soon  as  the  heat  strikes  the 
tubes,  the  circulation  of  the  water  begins.  The  water  nearest  the 
surface  of  the  tubes  becoming  warmer,  rises,  and  as  the  tubes  are 
higher  in  front,  this  water  flows  towards  the  front  water  leg 
where  it  rises  into  the  shell,  while  colder  water  from  the  shell 
falls  down  the  rear  water  leg  to  replace  that  flowing  forward  and 
upward  through  the  tubes.  This  circulation,  at  first  slow,  in- 

33 


514 


HANDBOOK    ON    ENGINEERING. 


creases  in  speed  as  soon  as  steam  begins  to  form.  Then  the 
speed  with  which  the  mingled  current  of  steam  and  water  rises  in 
the  forward  water  leg  will  depend  on  the  difference  in  weight  of 
this  mixture,  and  the  solid  and  slightly  colder  water  falling  down 
the  rear  water  leg.  The  cause  of  its  motion  is  exactly  the  same 
as  that  which  produces  draft  in  a  chimney. 


Fig.  269.     Plain  vertical  tubular  boiler. 

This  cut  shows  the  place  for  gauge  cocks  and  water  glass  in  an 

upright  boiler. 


HANDBOOK    ON    ENGINEERING. 


515 


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Fig.  270.     Showing  the  water-column  in  its  proper  place. 


516 


HANDBOOK    ON    ENGINEERING. 


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HANDBOOK    ON    ENGINEERING. 


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Fig.  271.    Showing  the  proper  place  for  closing  in  the  boiler  on 

the   side  — also   the  space   between   side  of   boiler  and 

side  walls. 


HANDBOOK   ON    ENGINEERING. 


521 


Fig.  272.    Showing   the   proper   place  for  grange-cocks  in   a  sub- 
merged tube  boiler. 


522 


HANDBOOK   ON    ENGINEERING. 


THE  AMOUNT  OF    MATERIAL   REQUIRED  TO  BRICK 
UP  BOILERS  OF  DIFFERENT  SIZE. 


•  Htt            • 

M        *5        *"• 

GO      . 
GO    OQ 

r^ 

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f 

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on 

—>  -^ 

73  ^ 

"S    £H                    §  'cS 

I? 

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1^ 

rC    «4H 

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pq 
•d 

S 

a;  a>  ^  ^2 

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ai  o 

IS 

a»  o  o  S  *2  'as 

u  a   - 

72"x22' 

18' 

10^500 

2,500 

18  bu. 

88 

8 

9  bbl. 

72"x20' 

18' 

10,000 

2,300 

18  bu. 

80 

8 

8  bbl. 

72"xl8' 

18' 

9,500 

2,200 

17  bu. 

72 

7 

8  bbl. 

60"x20' 

18' 

9;500 

2,200 

17  bu. 

80 

7 

8  bbl. 

60"xl8' 

18' 

9,000 

2,000 

16  bu. 

72 

7 

8  bbl. 

54"x20' 

18' 

8,700 

1,900 

15  bu. 

80 

6 

8  bbl. 

54"xl8' 

18' 

.     8,000 

1,800 

15  bu. 

72 

6 

8  bbl. 

54"xl6' 

18' 

7,500 

,700 

14  bu. 

64 

6 

7  bbl. 

48"xl8' 

18' 

7,500 

,600 

14  bu. 

72 

6 

7  bbl. 

48"xl6' 

18' 

7,200 

,500 

14  bu. 

64 

5 

•       7  bbl. 

42"xl8' 

18' 

7,000 

,400 

12  bu. 

72 

5 

7  bbl. 

42"xl6' 

18' 

6,500 

,300 

12  bu. 

64 

4 

7  bbl. 

If  13"  wall  i  less  on  Red  Brick. 

THE  DOWN  DRAUGHT  FURNACE. 

The  down  draught  furnace  is  known  as  being  one  of  the  best 
smoke  preventing  furnaces  in  the  market,  while  at  the  same  time 
the  cheapest  kind  of  coal  can  be  used. 

The  down  draught  furnace  makes  a -good  smoke  record,  even 
with  overworked  boilers,  doing  variable  work,  and  with  a  marked 
economy  in  fuel.  All  experience  with  the  down  draught  furnace, 
seems  to  indicate  that  smoke  from  boiler  furnaces  can  now  be 
abated  by  practical  means,  without  hardship,  no  matter  what  the 
type  of  boiler. 

Directions  for  firing  the    down   draught  furnace*  —  When 
firing  the  furnace,  throw  the  coal  evenly  over  the  entire  grate 
surface,  from  6    to    8   inches  in  depth,  a  little  heaviest   at  the 
rear    end    of    the    furnace.     Do   not  put    in  too  much    coal  — 
burn      more     air      and      economize     fuel     if      possible,     and 


HANDBOOK    ON    ENGINEERING. 


523 


do  not  pile  up  the  coal  in  front  near  the  door.  Never  fire  any 
fresh  coal  on  the  lower  grates  ;  let  in  air  below  the  lower  grates. 
When  poking  the  fire,  run  the  slice-bar  down  between  the  water 
grates  and  back  the  full  length  of  the  grates  ;  then  rafse  the  slice- 
bar  and  gently  shake  the  coal,  and  then  pull  it  out  without  stir- 
ring up  the  fire.  Never  turn  the  fire  over  so  that  black  coal  gets 
down  upon  the  water  grates,  unless  there  is  a  large  clinker  to  re- 
move. Never  give  the  top  grates  a  general  cleaning,  so  as  to 
leave  a  portion  of  the  grates  uncovered  and  the  remainder  with  a 
hot  lire  on  them,  as  this  causes  an  uneven  expansion  in  the  differ- 
ent tubes  forming  the  water  grates,  and  is  liable  either  to  bend 
the  tubes  or  strip  off  the  threads  where  they  enter  the  drums. 
When  the  top  fire  becomes  clogged  with  clinkers  so  that  it  is  hard 


r 


Fig.  273.    Down  draught  furnace. 


to  keep  up  steam,  run  in  the  slice-bar  and  raise  the  clinkers  to 
the  top  of  the  fire  ;  remove  the  large  clinkers,  leave  the  small  ones 
alone,  and  put  on  afresh  fire.  The  lower  grates  must  have  proper 


524 


HANDBOOK   ON    ENGINEERING. 


attention.  The  coals  must  be  raked  over  evenly  and  all  holes 
filled  up,  particular  care  being  taken  that  the  grates  are  perfectly 
covered  all  over.  If  considerable  coals  have  accumulated  on  the 


••jjfJL 7-i~- -litr-i 

. . yO-l" J 


Fig.  274.    Yiew  of  the  down  draught  furnace. 

lower  grates  and  the  air  spaces  are  closed  with  ashes  or  clinkers, 
the  slice-bar  must  be  used  and  the  clinkers  raised  up  and  turned 
over  and  the  larger  ones  removed.  It  is  best  to  remove  the  clink- 
ers every  two  or  three  hours,  leaving  the  coals  to  burn  up. 

SPECIFICATIONS  FOR  ONE    SIXTY-INCH     HORIZONTAL     SIX- 
INCH   FLUE  BOILER. 

General  directions*  —  There  will  be  one  boiler  20  feet  long  from 
out  to  out  of  heads  and  60  inches  inside  diameter. 

Material,  quality,  thickness,  etc*  —  Material  in  shell  of  the 
above  named  boiler  to  be  made  of  homogeneous  flange  steel  T5F" 
thick,  having  a  tensile  strength  of  not  less  than  60,000  Ibs.  to 


HANDBOOK   ON   ENGINEERING. 


525 


526  HANDBOOK    ON    ENGINEERING. 

the  square  inch  of  section,  with  not  less  than  56  per  cent  ductil- 
ity, as  indicated  by  contraction  of  area  at  point  of  fracture  under 
test,  or  by  an  elongation  of  25  per  cent  in  length  of  8  inches. 
Heads  must  be  ^"  thick  and  of  the  same  quality  of  steel  as  that 
in  the  shell.  All  plates  and  heads  must  be  plainly  stamped  with 
the  maker's  name,  and  tensile  strength. 

Tubes,  size,  number  and  arrangement*  —  The  boiler  must 
contain  18-6"  lap- welded  flues,  riveted  to  the  heads  with  ten  £" 
rivets  in  each  head  ;  said  flues  must  be  made  of  charcoal  iron  of  the 
best  American  make,  standard  thickness,  equal  to  the  National 
Tube  Works  Company's  make.  All  flues  must  have  at  least  3 
inch  clear  space  between  them,  and  not  less  than  3  inches 
between  flues  and  shell.  All  flanging  of  heads  must  be  free  from 
flaws  or  cracks  of  any  description,  and  properly  annealed  in  an 
annealing  oven  before  riveting  to  the  boiler.  If  4-inch  flues  are 
wanted  in  place  of  6 -inch,  the  boiler  must  have  44  best  lap- 
welded  tubes,  4"  in  diameter  and  20  feet  long,  set  in  vertical  and 
horizontal  rows,  with  a  clear  space  between  them,  vertically  and 
horizontally  of  !£",  except  the  central  vertical  space,  which  is  to 
be  4  inches.  Holes  for  tubes  to  be  neatly  chamfered  off  on  the 
outside.  Tubes  to  be  set  with  a  Dudgeon  expander,  and  beaded 
down  at  each  end. 

Riveting*  —  The  longitudinal  •  seams  of  the  boiler  must  be 
above  the  fire  line,  and  have  a  TRIPLE  row  of  rivets  ;  all  rivets  to 
be  |"  in  diameter ;  and  all  rivets  to  be  of  sufficient  length  to 
form  upheads  equal  in  size  to  the  pressed  heads  of  same.  The 
rivets  in  the  longitudinal  seams  must  be  spaced  3J"  apart 
from  center  to  center,  and  the  rows  of  same  to  be  pitched  2T3^" 
apart  from  center  to  center,  so  as  to  give  an  efficiency  of  the 
joint  of  TYo-  per  cent  of  the  solid  plate.  Transverse  seams  to 
be  single  riveted  with  same  size  rivets  as  those  in  the  longitudinal 
seams  pitched  2"  apart  from  center  to  center.  Care  must  be 
taken  in  punching  and  drilling  holes  that  they  may  come  fair  in 


HANDBOOK    ON    ENGINEERING.  527 

construction;  the  use  of  adrift-pin  to  bring  blind,  or  partially 
blind  holes  in  line  will  be  sufficient  cause  for  the  rejection  of 
the  boiler. 

Calking*  —  The  edges  of  the  plates  to  be  planed  and  beveled 
before  making  up  the  boilers,  and  the  calking  to  be  done  with 
round  nose  tools,  pneumatically  driven ;  no  split  or  wedge  calk- 
ing will  be  allowed. 

Bracing* —  There  must  be  22  braces  in  the  boiler,  one  inch  area 
at  least,  be  nine  above  the  flues  on  the  front  head  and  nine  similar 
ones  on  the  back  head,  none  of  which  shall  be  less  than  3'  6"  long, 
made  of  good  refined  iron  and  securely  riveted  to  the  heads ;  the 
other  end  to  be  extended  to  the  shell  of  boiler  and  riveted  thereto 
with  two  £''  rivets.  Care  must  be  exercised  in  the  setting  of 
them,  so  they  may  bear  uniform  tension.  There  must  be  two 
braces  below  flues,  one  on  each  side  of  manhead,  and  riveted  to 
the  heads  with  two  X"  rivets.  The  back  end  of  brace  to  be  ex- 

o 

tended  backward  to  side  of  shell  and  riveted  thereto  by  means 
of  two  J"  rivets ;  and  two  braces  in  back  end  above  flues,  one 
on  each  side  and  riveted  the  same  as  the  other  two  below 
flues. 

Manholes*  —  The  boiler  to  have  two  manholes  of  the  Hercules 
or  Eclipse  pattern,  same  to  be  of  size  10"  x  15",  one  located  in 
front  head,  beneath  the  flues,  and  the  other  in  rear  head  above 
the  flues,  and  each  to  be  provided  with  a  lead  gasket,  grooved  lid, 
two  yokes  and  two  bolts.  The  proportion  of  the  whole  to  be 
such  as  will  leave  it  as  strong  as  any  other  portion  of  the  head  of 
like  area. 

Steam  drum*  —  The  boiler  must  be  provided  with  one  steam 
drum  30"  in  diameter  by  5'  in  length,  shell  plates  of  which  are  to 
be  Ty  thick  and  heads  |"  thick,  of  the  same  quality  of  material 
as  that  in  the  boiler.  The  heads  must  be  bumped  to  a  radius  so 
as  to  give  as  near  as  practicable  equal  strength  as  to  that  in  the 
shell  without  bracing.  The  longitudinal  seams  of  the  drum  are 


528  HANDBOOK    ON   ENGINEERING. 

to  be  double  riveted  with  -J--J-"  diameter  rivets,  pitched  2J"  apart 
from  center  to  center,  so  as  to  give  an  efficiency  of  the  joint  of 
74  per  cent  of  the  solid  plate. 

Manhole  in  drum* — The  drum  must  be  provided  with  Her- 
cules or  Eclipse  patented  manhole,  same  to  be  of  size  10"xl5", 
located  in  the  center  of  one  head,  and  to  be  provided  with  a 
grooved  lid,  lead  gasket,  two  jokes  and  two  bolts.  The  propor- 
tion of  the  whole  to  be  such  as  will  leave  it  as  strong  as  any  other 
portion  of  the  head  of  like  area. 

To  attach  to  boilers.  —  The  steam  drum  must  be  attached  to 
the  boiler  by  means  of  two  flange  steel  connecting  legs,  8"  in 
diameter  by  12"  in  length,  and  securely  riveted  to  boiler  and 
steam  drum  shell. 

Mud  drum*  —  Boiler  must  be  provided  with  one  mud  drum 
24"  in  diameter  and  of  sufficient  length  so  that  each  end  may 
come  flush  with  the  outside  of  the  boiler  walls  on  each  side  ;  the 
quality  and  thickness  of  steel  to  be  the  same  as  that  specified  for 
the  steam  drum,  and  all  seams  to  be  single  riveted ;  said  mud 
drum  to  be  provided  with  one  Hercules  or  Eclipse  patent  manhole 
in  one  end,  and  to  be  of  size  9"  x  14",  supplied  with  a  grooved 
lid,  lead  gasket,  two  yokes  and  two  bolts. 

To  attach  to  boiler*  —  The  mud  drum  is  to  be  attached  to 
boiler  by  means  of  8"  diameter  steel  connecting  leg,  about  16"  in 
length,  properly  riveted  to  boiler  and  mud  drum  shells. 

Flanges* — The  boiler  to  have  one  8"  wrought  steel  flange  riv- 
eted on  top  of  steam  drum ;  one  wrought  steel  flange  4"  in  diam- 
eter, about  5  feet  from  front  end  of  boiler  for  safety  valve  one 
2"  wrought  steel  flange  on  after  end  of  boiler  over  the  center  of 
mud  leg  for  supply  pipe  —  all  flanges  to  be  threaded  ;  2"  hole  in 
mud  drum  for  blow-off  ;  also  2  1J"  holes,  one  on  top  of  boiler 
and  one  on  end  near  bottom  of  boiler  for  water  column. 

Fusible  plugs*  —  To  have  two  fusible  plugs ;  one  inserted  in 
shell  from  inside  on  second  sheet,  or  about  5'  from  forward  end,  1 


HANDBOOK    ON    ENGINEERING.  529 

inch  above  flues  ;  one  plug  inserted  in  top  of  flue,  not  more  than 
three  feet  from  after  end. 

Trimmings*  —  Furnish  one  4"  spring  or  dead  weight  safety 
valve,  4"  diameter ;  one  water  combination  column  ;  provide  same 
with  two  1 J"  valves  for  the  steam  and  water  connections  between 
the  boiler  and  column,  and  one  %"  valve  for  blow-pipe  ;  said  blow- 
pipe to  be  connected  with  ashpit ;  said  combination  barrel  to  be 
4''  diameter,  IS'1  long,  and  made  of  cast-iron.  Also,  furnish  one 
water  gauge  having  a  f'x  15"  Scotch  glass  tube,  bodies  polished 
with  wood  wheels  and  guards,  rods,  bodies  threaded  f " ;  three 
gauge  cocks  |"  register  pattern,  polished  brass  bodies  ;  one  steam 
gauge  with  10"  dial;  one  2"  brass  feed  valve  with  2"  check 
valve ;  one  2"  gate  valve  for  blow-off  from  mud  drum ;  also  one 
asbestos  packed  stop-cock  for  same,  so  as  to  insure  against  the 
possibilities  of  a  leak  through  the  blow-pipe.  Water  column  to 
have  crosses  in  place  of  ells.  Crosses  to  have  brass  plugs. 

Castings,  gr ates,  doors,  etc*  —  The  boiler  must  be  provided 
with  a  heavy  three-quarter  fire  front  of  neat  design,  having  double 
firing  and  ashpit  doors,  anchor  bolts  for  anchoring  fire  cronts  in 
place,  heavy  deadplates,  a  full  set  of  fire  liners  9"  deep  for  sup- 
porting firebrick  on  end,  front  and  rear  bearing  bars  ;  a  full  set 
of  ordinary  grate  bars  4  ft.  long,  soot  door  and  frame  for  cleaning 
out  rear  ashpit ;  a  full  set  of  skeleton  arch  plates  ;  12  heavy  buck 
staves  9i'  long,  provided  with  tie  rods,  nuts  and  washers,  heavy 
back  stand  with  plate  and  expansion  rollers  ;  also  furnish  wrought 
plates  to  cover  mud  drum. 

Fire  tools*  —  Furnish  in  addition  to  above  two  sets  of  fire  tools 
consisting  of  two  pokers,  two  hoes,  two  slice-bars,  two  claws,  and 
one  six-inch  flue  brush  with  |"  pipe  for  handle. 

Breeching* — Boiler  must  have  a  breeching  fitted  to  front  head 
and  fastened  thereto  by  means  of  bolts,  stays  and  suitable  pieces 
of  angle  iron,  bent  to  conform  to  circle  of  boiler.  The  underside 
of  breeching  is  to  run  across  the  head  between  the  lower  flues  and 

34 


530  HANDBOOK    ON    ENGINEERING. 

the  manhole,  leaving  the  manhole  freely  exposed ;  the  sides  of 
breeching  are  to  be  made  of  T3¥"  steel,  the  front  and  doors  of  |" 
steel ;  said  doors  to  be  hung  by  means  of  strap  hinges,  provided 
with  suitable  fastenings  so  as  to  give  free  access  to  all  flues  when 
open. 

Uptake  and  damper*  —  An  uptake  having  an  area  of  1221 
square  inches  must  be  fitted  to  top  of  breeching.  Said  uptake 
must  be  of  convenient  form  for  attaching  to  a  stack  40"  in  diam- 
eter and  provided  with  a  close-fitting  damper  having  a  steel  hand 
attachment,  so  that  same  may  be  operated  conveniently  from  the 
boiler  room  floor. 

Smoke  stack*  —  There  is  to  be  provided  for  the  above  boiler 
one  smoke  stack  40"  in  diameter  by  90  feet  in  height,  half  of 
which  is  to  be  made  of  No.  8,  and  the  other  half  of  No.  10  best 
black  sheet  steel  throughout,  and  supplied  with  two  sets  of  four 
guy  rods,  each  consisting  of  f "  galvanized  wire  cable  guy  strand 
with  turn-buckles  for  same. 

In  general*  —  The  above-mentioned  boiler  must  be  made  of 
strictly  first-class  material  and  workmanship  throughout,  and  sub- 
jected to  a  hydrostatic  pressure  of  150  pounds  to  the  square  inch 
before  leaving  the  works  of  the  manufacture. 

Painting  boiler  breeching*  —  Smoke  stack  and  boiler  front, 
steam  and  mud  drum,  and  all  trimmings,  to  have  two  good  coats 
of  coal  tar. 

Masonry*  —  Boiler  to  be  set  in  good  substantial  masonry,  of 
hard  burned  brick  and  good  mortar,  made  of  clean,  sharp  sand 
and  fresh  burned  lime.  Walls  to  be  18"  thick0  The  outside  walls 
to  be  laid  up  of  selected  hard  burned  brick,  with  close  joints 
struck  smooth  and  rubbed  down.  The  sides,  end  and  bridge 
walls,  and  boiler  front,  to  have  a  foundation  of  24"  wide  and  12' 
deep,  laid  in  Portland  cement.  The  ash  pit  to  be  paved  with 
hard  burned  brick  set  on  edge  firmly,  imbedded  in  Portland 
cement.  For  a  distance  of  seven  feet  in  front  of  the  boiler  and 


HANDBOOK    ON    ENGINEERING.  531 

continuing  across  entire  width  of  front  of  boiler  setting  to  be 
paved  with  hard  burned  brick  set  on  edge,  firmly  imbedded  in 
sand.  The  walls  to  be  carried  up  to  the  full  height  and  a  row- 
lock course  of  brick  4"  thipk  to  be  carried  over  top  of  boiler  from 
side  wall  to  side  wall,  extending  the  whole  length  of  boiler,  and 
the  entire  arch  to  be  plastered  over  on  the  outside  with  mortar. 
The  bridge  walls  to  be  24",  carried  up  to  within  6"*  of  under 
side  of  boiler.  The  top  of  bridge  wall  to  be  of  fire  brick  and 
made  in  the  form  of  an  inverted  arch,  conforming  to  the  shell  of 
the  boiler.  The  space  under  boiler  and  back  of  bridge  wall  to 
the  back  end  of  boiler,  to  be  filled  in  with  earth  or  sand  and  the 
top  paved  with  brick,  and  tapering  from  bridge  wall  back  to  back 
end  to  12"*  at  back  end,  and  in  a  similar  form  and  shape,  that  is, 
inverted  arch.  The  uptake  for  returning  the  smoke  and  heat  at 
back  end  of  boiler,  to  be  arched  over  from  rear  wall  against  the 
back  head  of  boiler  2"  above  the  tubes,  the  arch  being  made  of  arch 
fire  brick,  and  backed  up  with  red  brick.  Furnace  to  be  lined 
throughout  with  first  quality  fire  brick,  dipped  in  fire  clay  with 
close  joints  and  fire  brick  rubbed  to  place,  from  a  point  2"  below 
grates,  to  where  it  safes  in  against  boiler,  and  to  be  continued  fire 
brick  as  far  back  as  the  rear  end  of  setting  and  across  rear  end  of 
same ;  it  being  the  intent  that  all  interior  surfaces  of  the  setting 
with  which  the  heat  comes  in  contact,  shall  be  faced  with  fire 
brick.  Every  sixth  course  to  be  a  header  course. 

Smoke  connections*  —  The  connection  from  boiler  to  chimney 
to  be  made  of  No.  12  black  iron,  with  cleaning  door  and  damper 
in  same. 

BANKING  FIRES. 

Different  engineers  pursue  different  methods  in  banking  fires. 

One  method  is  to  push  the  fire  back  one-third  towards  the  bridge 

wall,  and  clean  off  the  grate  in  front.     Then  shovel  in  from  150 

to  300  Ibs.  of  fine  coal  on  top  of  the  fire,  closing  ash-pit  doors 

*  These  distances  should  be  doubled  for  bituminous  coal. 


532  HANDBOOK    ON    ENGINEERING. 

and  leaving  furnace  doors  open,  with  damper  open  enough  to  let 
the  gases  escape.  Others  bank  after  this  fashion  but  close  all 
doors  and  air  holes,  leaving  the  damper  partially  open.  Another 
method  is  to  level  the  fire  all  over  the,  grate,  and  shovel  in  from 
150  to  500  Ibs.  of  fine  coal,  —  depending  on  the  size  of  the 
grate, — and  then  cover  the  whole  surface  with  wet  ashes  to  a 
good  depth,  so  that  no  fire  nor  flame  can  be  seen,  then  close  the 
ash-pit  doors,  leaving  the  furnace  doors  ajar,  and  leave  the 
damper  partially  open  so  that  the  gases  may  escape.  In  the 
morning,  rake  out  the  ashes,  clean  the  fire,  and  throw  in  fresh 
coal. 

INSTRUCTIONS  FOR  BOILER  ATTENDANTS. 

The  following  instructions  apply  more  particularly  to  horizontal 
return  tubular  boilers,  although  in  a  general  way  they  are  appli- 
cable to  all  types  of  boilers. 

Never  start  a  fire  under  a  boiler  until  you  are  positively  certain 
that  there  is  sufficient  water  in  the  boiler,  — at  least  two  gauges 
of  water.  Do  not  trust  to  the  water  gauge  alone,  but  try  the 
gauge  cocks  also,  and  try  them  at  intervals  during  the  day,  be- 
cause the  water  gauge  pipe  connections  may  be  choked  and  cause 
a  false  water  level. 

Before  starting  a  fire  be  sure  that  the  blow-off  cock  is  closed 
and  not  leaking. 

Before  it  is  time  to  start  the  engine,  pump  up  three  gauges  of 
water,  and  blow  off  one  gauge,  in  order  to  get  rid  of  mud  and 
other  sediment.  If  the  boiler  b.as  a  surface  blow-off,  —  commonly 
called  a  ct  skimmer," — blow  off  the  scum  before  stopping  the 
engine  for  the  day. 

When  the  day's  work  is  done,  leave  three  gauges  of  water  in 
the  boiler,  to  allow  for  leakage  and  evaporation  during  the  night. 

Never  raise  steam  hurriedly.  Sudden  changes  of  temperature 
may  produce  fractures,  or  start  leaks. 


HANDBOOK   ON   ENGINEERING.  533 

la  starting  a  fire  in  a  furnace,  a  good  plan  is  to  cover  the  grate 
with  a  thin  layer  of  coal  and  to  place  the  shavings  and  wood  on 
the  coal  and  then  light  the  shavings. 

The  advantage  of  placing  a  covering  of  coal  on  the  grate  before 
the  wood  and  shavings,  is  that  it  is  a  saving  of  fuel,  as  the  heat 
that  would  be  transmitted  to  the  bars  is  absorbed  by  the  coal,  and 
the  bars  are  also  protected  from  the  extreme  heat  of  the  fresh 
fire. 

Lift  the  safety-valve,  — if  of  the  lever  pattern,  —  every  morn- 
ing while  raising  steam,  and  satisfy  yourself  that  it  is  in  good 
working  order,  and  that  the  ball  is  set  at  the  proper  point  on  the 
lever.  The  most  disastrous  explosions  have  occurred  with  boilers 
whose  safety-valves  had  been  stuck  down  or  overloaded. 

Keep  the  boiler  shell  free  of  soot.  Soot  is  a  very  good  non- 
conductor of  heat,  and  considered  worse  than  scale  inside  of  a 
boiler. 

Keep  your  boiler  tubes  free  from  soot  and  dust.  Choked  tubes 
impair  the  draft.  The  tubes  should  be  cleaned  twice  a  week,  or 
oftener. 

Soot  collects  also  in  a  stack  or  chimney  and  in  the  connection 
between  the  breeching  and  stack,  and  interferes  with  the  draft, 

Open  your  boiler  every  two  weeks,  or,  as  often  as  necessary,— 
depending  on  the  kind  of  feed-water  used,  —  and  clean  out  the 
mud  and  scale.  At  the  same  time  examine  all  of  the  stays,  and 
see  that  they  are  taut  and  in  good  order.  Also,  look  for  pitting 
around  the  mud-drum  connection,  and  for  grooving  in  the  side 
seams.  Examine  all  outlets  and  pipe  connections,  and  look  for 
indications  of  "  bagging  "  in  the  furnace  sheets. 

Clean  off  the  fusible  plugs  both  inside  and  outside  of  the  boiler. 
A  fusible  plug  covered  with  soot  on  the  fire  side,  and  with  scale 
on  the  water  side,  is  no  longer  a  u  safety  plug."  Renew  the 
filling  in  safety  plugs,  at  least  once  a  year.  They  are  filled  with 
pure  Banca  tin. 


534  HANDBOOK   ON    ENGINEERING. 

Be  perfectly  satisfied  that  your  boiler  is  in  good  condition 
internally  before  you  close  it  up. 

Just  as  soon  as  you  have  fastened  the  man-head  in  its  place > 
turn  on  the  feed-water  until  you  get  at  least  three  gauges  of  water. 
Fires  have  been  built  under  empty  boilers,  and  will  be  again,  if 
you  forget  to  turn  on  the  feed  water  after  cleaning  out. 

Do  not  empty  a  boiler  while  it  is  under  steam  pressure,  but 
allow  it  to  get  cold  before  letting  the  water  run  out. 

If  you  are  in  a  great  hurry  and  can't  wait  for  the  boiler  to  cool 
down,  nor  for  the  brickwork  or  anything  else  to  cool  down,  draw 
the  fire  and  open  the  furnace  and  ash-pit  doors,  then  turn  on  the 
feed  water,  and  from  time  to  time  blow  out,  until  the  steam  gauge 
shows  no  pressure ;  then  shut  .off  the  feed-water,  raise  the  safety 
valve,  open  the  blow-off  cock,  then  open  up  the  boiler. 

Before  opening  a  man -hole,  lift  the  safety-valve,  so  as  to  be 
sure  that  there  is  neither  pressure  nor  vacuum  in  the  boiler. 

Look  well  after  the  brick -work  surrounding  your  boiler,  and 
stop  all  cracks  in  the  walls  with  mortar  or  cement,  as  soon  as 
discovered.  They  impede  the  draft,  and  cool  the  plates  of  the 
boiler,  causing  a  waste  of  fuel. 

See  that  the  bridge  wall  is  in  perfect  condition,  because  a  gap 
in  the  bridge  wall  might  cause  a  "  bag  "  in  the  boiler  by  concen- 
trating the  flames  on  one  spot. 

Never  allow  any  bare  places  on  the  grate,  nor  any  accumulation 
of  ashes,  or  dead  coal  in  the  corners  of  the  furnace,  as  such 
places  admit  great  quantities  of  cold  air  into  the  furnace,  and 
render  the  combustion  very  imperfect. 

In  firing  with  anthracite  coal,  do  not  poke  and  stir  up  the  fire, 
as  with  soft  coal,  but  let  it  alone. 

In  firing  soft  slack  coal,  fire  very  lightly  but  frequently,  carry- 
ing a  thin  fire. 

In  firing  with  soft  lump  coal,  carry  a  thick  fire,  say  from  six 
to  eight  inches  deep,  according  to  the  size  of  the  furnace. 


HANDBOOK    ON    ENGINEERING.  535 

In  firing  up,  you  may  spread  the  fresh  coal  evenly  all  over  the 
grate,  or,  you  may  push  the  live  coals  back  towards  the  bridge- 
wall,  leaving  a  thin  bed  of  live  coals  near  the  furnace  doors,  and 
spreading  the  fresh  coal  on  top  of  it.  This  is  called  carrying  a 
coking  fire.  Some  prefer  the  one  and  some  the  other  method  of 
firing. 

In  case  you  should  find  the  water  in  the  boiler  out  of  sight, 
and  a  heavy  fire  in  the  furnace,  don't  get  rattled,  and  don't  lose 
your  head.  Open  the  furnace  doors,  and  close  the  ash-pit  doors, 
and  cover  the  fire  with  wet  ashes,  or  damp  clay,  completely 
smothering  it.  Let  everything  else  alone,  including  the  safety 
valve  and  the  engine.  Now  wait  until  the  boiler  cools  down  and 
the  gauge  shows  no  pressure,  then  turn  on  the  feed-water. 

On  the  other  hand,  if  there  is  but  very  little  fire  in  the  furnace, 
you  may  draw  the  fire,  instead  of  covering  it  with  ashes  or  clay. 

If  your  boiler  foams  badly  and  you  are  uncertain  as  to  the 
water  level,  stop  the  engine,  and  the  true  water  level  will  show 
itself  at  once. 

If  your  boiler  primes  and  water  is  carried  over  to  the  engine, 
it  shows  that  there  is  want  of  sufficient  steam  room  in  the  boiler. 
Either  put  a  dry-pipe  in  the  boiler,  or,  increase  the  steam  pressure 
if  the  boiler  will  safely  stand  it. 

Never  attempt  to  calk  a  leaky  seam  in  a  boiler  under  steam 
pressure,  because  the  jar  caused  by  the  hammer  blows  might 
cause  a  rupture  of  the  seam.  Better  to  be  on  the  safe  side 
always  when  repairs  are  required  in  a  steam  boiler,  and  wait  until 
the  boiler  is  cold.  The  above  applies  to  steam  pipes  and  valve 
casings,  also. 

Never  open  any  steam  valves  suddenly,  nor  close  them  sud- 
denly either,  because  it  is  highly  dangerous  to  do  so,  particularly 
if  there  is  considerable  water  in  the  pipes.  The  effect  is  the  same 
as  water  hammer  in  water  pipes. 

Smoke  is  caused  by  too  little  air  supply,  or  by  the  flames  being 


536  HANDBOOK   ON   ENGINEERING. 

prematurely  cooled.  Therefore,  after  firing  up  with  fresh  coal, 
it  might  be  necessary  to  leave  the  furnace  doors  ajar  in  order  to 
supply  sufficient  air  above  the  fuel. 

Remember  that  it  takes  nearly  24  cubic  feet  of  air  for  the 
proper  combustion  of  one  pound  of  soft  coal.  Hard  coal  does 
not  require  so  much. 

Each  and  every  boiler  in  a  battery  should  have  its  own  inde- 
pendent safety-valve  and  steam  gauge. 

If  you  are  obliged  to  force  your  fire,  watch  your  furnace  sheets 
for  indications  of  "  bagging,"  if  the  water  space  below  the  lowest 
row  of  tubes  is  cramped.  Water-tube  boilers  are  less  liable  to 
suffer  from  the  effects  of  forced  fires  than  shell  boilers. 

With  an  intensely  hot  fire  under  a  shell  boiler,  the  furnace 
sheets  are  liable  to  bag,  unless  there  is  ample  water  space  be* 
tween  the  shell  of  the  boiler  and  the  bottom  row  of  tubes. 

The  use  of  mineral  oil  to  remove  or  prevent  boiler  scale,  is  not 
to  be  recommended. 

Have  your  feed  water  analyzed,  and  use  a  scale  preventer 
adapted  to  its  requirements. 

By  all  means  endeavor  to  secure  a  steady  furnace  temperature, 
and  a  steady  steam  pressure,  for  herein  lies  much  economy  of 
fuel.  Fluctuations  are  wasteful. 

Put  a  damper  in  your  chimney  and  adjust  it  to  the  needs  of 
your  furnace.  Try  to  prevail  on  your  employer  to  put  in  a  shak- 
ing grate.  It  will  enable  you  to  carry  a  steady  furnace  temper- 
ature, and  also  enable  you  to  keep  the  air  spaces  in  your  grate 
free  and  open  without  breaking  up  your  fire. 

RULES  AND  PROBLEMS  RELATING  TO  STEAM  BOILERS. 

To  find  the  safe  working  pressure :  — 

U*  S*  Rule.  —  Multiply  one-sixth  (|)  of  the  lowest  tensile 
strength  found,  stamped  on  any  plate  in  the  cylindrical  shell, 


HANDBOOK  ON    ENGINEERING.  537 

by  the  thickness  —  expressed  in  inches  or  parts  of  an  inch  —  of 
the  thinnest  plate  in  the  same  cylindrical  shell,  and  divide  by  the 
radius  or  half  diameter  —  also  expressed  in  inches  —  and  the 
result  will  be  the  pressure  allowable  per  square  inch  of  surface 
for  single  riveting ;  to  which  add  20  per  cent  for  double  riveting, 
when  all  the  holes  have  been  "  fairly  drilled  "  and  no  part  of 
such  hole  has  been  punched. 

A*  S.  of  M*  E*  Rule*  —  First,  find  the  tensile  strength  of  the 
solid  plate  between  the  centers  of  two  adjacent  rivet  holes.  Call 
this  factor  A.  • 

Next,  find  the  tensile  strength  of  the  solid  plate  between  the 
centers  of  two  adjacent  rivet  holes,  less  the  diameter  of  one  rivet 
hole.  Call  this  factor  B. 

Next,  find  the  shearing  strength  of  the  rivets.  Call  this 
factor  C. 

Now  divide  whichever  is  the  smaller  factor  B  or  C  by  J.,  and 
the  quotient  will  give  the  strength  of  the  joint  as  compared  with 
the  solid  plate  —  expressed  as  a  percentage.  Then  multiply  the 
tensile  strength  of  the  plates  by  the  thickness  of  plates  —  in  frac- 
tional parts  of  an  inch  —  and  multiply  this  product  by  the  per- 
centage as  found  above,  and  divide  this  last  product  by  the 
radius  of  the  shell  in  inches,  and  the  quotient  will  be  the  bursting 
pressure. 

Divide  this  quotient  by  the  factor  of  safety  and  the  result  will 
give  the  safe  working  pressure. 

Example*  —  What  is  the  safe  working  pressure  for  a  steel 
boiler  60  inches  in  diameter,  with  side  seams  double  riveted, 
tensile  strength  of  plates  60,000  Ibs.  per  sqr.  in.,  thickness  of 
plate  |  inch.  Diameter  of  rivet  holes  £f  inch,  pitch  of  rivets  3J 
inches,  shearing  strength  of  rivets  38,000  Ibs.  per  sqr.  in.,  and 
factor  of  safety  5  ? 

Ans.  By  U.  S.  rule,  150  Ibs.  per  sqr.  in. 
By  A.  S.  of  M.  E.  rule,  106J  Ibs.  per.  sqr.  in. 


538  HANDBOOK   ON   ENGINEERING. 

Operation  by  U.  S.  rule :  — 

60,000 

— ^ —  =  10,000.     And,  10,000  X  f  =  37,500. 

3750 
And,    -3Q-=  125.     And,  125  X. 20  =25. 

Then,   125+25  =  150, 

Operation  by  A.  S._of  M.  E.  rule:  — 
f"  =  .3  75". 

I*"  =  . 9375". 

Then,  60,000  X  3J  X  .375  =  73,125  Ibs.,  the  strength  of  the 
solid  plate  between  the  centers  of  two  adjacent  rivet  holes.  Call 
this  factor  A.  Also,  3J-  =  3.25. 

Then,  3.25  —  .9375  =  2.3125. 

And,  60,000  X  2.3125  X  .375  =  52,031.25  Ibs.  the  strength 
of  the  plate  between  two  adjacent  rivet  holes.  Call  this  factor  B. 

Then,  .9375  X  -9375  X  .7854  =  .69029  of  a  square  inch,  the 
area  of  one  rivet  hole.  There  are  two  rows  of  rivets. 

Then,  .69029  X  2  =  1.38058  sqr.  ins.  the  area  of  two  rivet 
holes  combined. 

Then,  38,000  X  1.38058  =52,462.04  Ibs.,  the  resistance  of 
rivets  to  shearing.  Call  this  C.  Now  since  B  is  less  than  (7, 
divide  52,031.25  by  73,125  and  get  as  a  quotient  .71 +,  thus 
showing  the  strength  of  the  joint  to  be  more  than  71  per  cent  of 
the  strength  of  the  solid  plates. 

Then,  60,000  X^875  X  .71  =  ^5  ^  per  sqr<  .^  ^ 
bursting  pressure. 

And,    L-  =   106.5   Ibs.  per   sqr.    in.,  the   safe   working 

5 

pressure. 


HANDBOOK   ON   ENGINEERING.  539 

To  find  the  horse  power  of  a  horizontal  return  tubular  boiler, 
from  its  heating  surface  :  — 

Rule*  —  Find  the  heating  surface  in  square  feet,  of  the  shell 
of  the  boiler,  measuring  from  one  fire  line  to  the  other.  Next 
find  the  internal  heating  surface  of  all  the  tubes  in  square  feet. 
Add  the  two  results  together  and  divide  their  sum  by  12,  and  the 
quotient  will  be  the  H.  P.  approximately.  The  heads  are 
omitted. 

Example*  —  What  is  the  H.  P.  of  a  horizontal  return  tubular 
boiler  60  inches  in  diameter  and  20  feet  long,  with  44  four-inch 
tubes  each  20  feet  long,  the  distance  from  fire  line  to  fire  line 
being  9  feet?  Ans.  86.65  H.  P. 

Operation*  —  The  internal  diameter  of  a  4-inch  tube  is  3.732 
inches. 

Then,  20  X  9  —  180  square  feet  of  heating  surface  in  the 
shell. 


3.732  X3-!41^        .9770376   ft.,  the    circumference   of 

12 

one  tube  in  feet. 

And,  .9770376  X  20  X  44  =  859.793  +  sqr.  ft.,  the  total 
heating  surface  of  the  tubes. 

Then,   180+859-793  =  86.65  nearly. 
12 

To  find  the  factor  of  evaporation  :  — 

Rule.  —  From  the  total  number  of  heat  units  in  one  pound  of 
steam  at  the  given  pressure,  subtract  the  number  of  heat  units  in 
one  pound  of  the  feed  water  at  its  given  temperature,  and  divide 
the  remainder  by  965.7,  which  is  a  constant. 

Example*—  A  boiler  evaporates  6,000  Ibs.  of  water  per  hour 
from  feed  water  at  210  degrees  into  steam  at  125  Ibs.  gauge  pres- 


540  HANDBOOK   ON   ENGINEERING 

sure,  what  is  the   equivalent  evaporation  "  from  and  at,"  212°? 
What  is  the  H.  P.  of  the  boiler? 

Ans.  Equiv.  evap.  6276  Ibs. 
H.  P.  182,  nearly. 

Operation*  —  The  total  number  of  heat  units  in  steam  at  125 
Ibs.  per  sqr.  in.  gauge  pressue  is  1221.5351. 

The  number  of  heat  units  in  feed-water  at  210  degrees 
equals  210.874.  The  latent  heat  of  steam  at  atmospheric  pres- 
sure, equals  965.7. 

Then,  1221.5351  —  210.874  =  1010.6611. 

And,   -    —  '-  —  —  =  1.046,  the  factor  of  evaporation. 
965.7 

And,  6000  X  1-046  =  6276  the  equivalent  evaporation. 


Then,  =  181.9  H.  P. 

34.5 

To  find  how  many  pounds  of  steam  at  a  given  absolute  pressure 
will  flow  through  an  orifice  of  one  square  inch  area  in  one  sec- 
one?  :  — 

Rule*  —  Divide  the  absolute  pressure  by  the  constant  number  70. 

Example*  —  How  many  pounds  of  steam  at  85  Ibs.  per  sqr.  in. 
gauge  pressure,  will  flow  through  an  orifice  one  inch  in  diameter, 
in  one  second?  Ans.  1.122  Ibs. 

Operation*  —  A  hole  1  inch  in  diameter  has  an  area  of  .7854 
of  a  sqr.  inch. 

And  85  +  15  =  100  Ibs.  absolute. 

Then,  122 


The  weight  of  a  cubic  foot  of  steam  at  100  Ibs.  per  sqr.  in. 

1  122 
absolute  pressure  is  .2307  of  a  pound.     Then,     '  Q?i   =  4.86  -{- 

cubic  feet. 


HANDBOOK    ON   ENGINEERING.  541 

To  find  the  width  of  a  reinforcing  ring  for  a  round  hole  in  a  flat 
surface,  when  the  ring  must  contain  as  many  square  inches  as 
were  cut  out  of  the  plate,  and  when  the  ring  and  the  plate  are  of 
the  same  thickness  :  — 

Rule* — Find  the  area  of  the  hole  in  square  inches  and  multi- 
ply it  by  2.  Divide  this  product  by  .7854  and  extract  the  square 
root  of  the  quotient  for  the  diameter  of  the  ring  over  all.  Sub- 
tract the  diameter  of  the  hole  from  the  diameter  over  all,  and 
divide  the  remainder  by  2  for  the  width  of  the  ring. 

Example*  —  What  should  be  the  width  of  a  reinforcing  ring  for 
a  hole  10  inches  in  diameter,  the  metal  cut  out,  and  the  metal  in 
the  ring  being  |  in.  thick?  Ans.  2T^  inches. 

Operation* —  10  X  10  X  .7854  =  78.54  sqr.  ins.  area  of  hole. 

And,  78.54  X  2  •=  157.08  sqr.  ins.  in  both  hole  and  ring. 
157.08 

And'     T7854": 

And, 


And,    14.142  — 10  z=  4.142. 

•      4.142 
Then,  — ~ —  —  2.071"  or  practically  2^". 

To  find  the  width  of  a  reinforcing  ring  for  an  elliptical  manhole 
in  a  flat  surface,  when  the  ring  must  contain  as  many  square 
inches  as  are  contained  in  the  hole,  and  the  metal  cut  out  and 
metal  in  the  ring  are  of  the  same  thickness :  — 

Rule*  —  Square  the  short  diameter  of  the  hole  and  add  to  it  six 
times  the  short  diameter  multipled  by  the  long  diameter,  and  to 
this  product  add  the  square  of  the  long  diameter,  and  extract  the 
square  root  of  the  sum.  From  this  root  subtract  the  sum  of  the 
short  diameter  added  to  the  long  diameter,  and  divide  the  re- 
mainder by  4  for  the  width  of  the  ring. 

Example*  —  What  should  be  the  width  of  a  reinforcing  ring 
for  a  manhole  11"  X  15"?  Ans.  2J£  inches. 


542  HANDBOOK   ON   ENGINEERING. 

Operation.—  11"  X  11"  =  121. 

And,  11  X  15  X6=990. 

And,  15  X  15  =  225. 

Then,  121  +  990  +  225  =  1336. 

And,  V 1336  =  36.551.' 

And,  11  +  15  =  26. 

Then,  36.551  —  26  =  10.551. 

10.551 

And,  — j —  =  2.637  +  ins.  the  width  of  the  ring,  or,  prac- 
tically 2J£  ins. 

Then,  2.637X2  =  5.274". 

And,  11  +  5.274  =  16.274"  short  diameter  of  ring  over  all. 

And,  15  +  5.274  =  20.274"  long  diameter  over  all. 

Proof:  20.274  X  16.274  X  .7854=  259.13  +  square  inches 
area  of  hole  and  ring. 

And,  15  X  11  X  -7854  =  129.59  +  sqr.  ins.  area  of  hole  alone. 

Then,  259.13—129.59  =  129.54. 


THE  AHOUNT  OF  STEAM  USED  WITH  VALVE  OPEN  WIDE, 
WITH  STEAfl  JETS  AS  A  SMOKE  PREVENTIVE. 

STEAM    JETS. 

Given  two  boilers  with  separate  furnaces,  having  4  steam  jets 
in  each  furnace,  and  each  jet  T^-  inch  in  diameter,  the  steam  pres- 
sure being  100  Ibs.  per  sqr.  inch  by  the  gauge.  How  many 
pounds  of  steam  at  this  pressure  will  flow  through  the  8  nozzles 
in  12  hours?  Answer.  1739  Ibs.  nearly. 

Operation :  TV"  =  .0625  ". 

Then,  .0625  X  -0625  X  .7854  =  .003067968750  sqr.  inch, 
area  of  1  jet. 


HANDBOOK   ON    ENGINEERING.  543 

And,  .003067968750  X  8  =  .02454375  sqr.  inch,  the  com- 
bined area  of  8  jets. 

Also,  100  +  15  =  115  Ibs.  per  sqr.  inch,  the  absolute  steam 
pressure, 

115 
And,  _ —  =  1.64   Ibs.  of  steam    per  second  that  will  flow 

through  an  orifice  of  1  square  inch  area. 

Then,  1.64  X  .02454375  =  .04025175  Ibs.  of  steam  per  second 
flowing  through  the  8  jets. 

Again:  There  are  43,200  seconds  in  12  hours. 
Thus:   12X60X60  =  43,200. 

Then,  .04025175  X  43,200  =  1738.8756  Ibs.  of  steam  will 
flow  through  8  jets  in  12  hours'  time. 

Taking  a  high  speed  automatic  cut-off  engine  using  20  Ibs.  of 
steam  per  H.  P.  per  hour,  the  8  steam  jets  would  waste  enough 
steam  in  12  hours  to  run  — 

A  10  H.  P.  engine  for  8£  hours. 
A  20      "         "         "   4£       " 
A  40      "         "         "   2J        • 
An  80      "         "         "    1^     « 

Thus  10  X  20  =  200. 
And,  — _  =  8i  nearly. 

9OO 

20  X  20  =  400. 

And,   =  4i  nearly. 


80  X  20  =  1600. 

And,  — f —  =  lA  nearly. 
1  1600  J 


544 


HANDBOOK    ON 


CHAPTER     XIX 


THE  STEAM  PUMP, 


Fig.  276.    The  Worthington  compound  pump. 

THE  WORTHINQTON  COMPOUND  PUMP. 

In  the  arrangement  of  steam  cylinders  here  employed,  the  steam 
is  used  expansively,  which  cannot  be  done  in  the  ordinary  form. 
Having  exerted  its  force  through  one  stroke  upon  the  smaller 
steam  piston,  it  expands  upon  the  larger  during  the  return  stroke, 
and  operates  to  drive  the  piston  in  the  other  direction.  This  is, 
in  effect,  the  same  thing  as  using  a  cut-off  on  a  crank  engine, 
only  with  the  great  advantage  of  uniform  and  steady  action  upon 
the  water. 


HANDBOOK   ON    ENGINEERING. 


645 


Compound  cylinders  are  recommended  in  any  service  where 
the  saving  of  fuel  is  an  important  consideration.  In  such  cases, 
their  greater  first  cost  is  fully  justified,  as  they  require  30  to  33 
per  cent  less  coal  than  any  high-pressure  form  on  the  same  work, 


Fig.  277.    Showing    a   sectional    view    of    the  Wortliington 
compound   pump. 

This  cut  shows  the  steam  valves  properly  set. 


On  the  larger  sizes,  a  condensing  apparatus  is  often  added,  thus 
securing  the  highest  economical  results. 

Any  of  the  ordinary  forms  of  steam  pumps  can  be  fitted  with 
compound  cylinders. 

It  should  be  remembered  that,  as  the  compounds  use  less  steam 
their  boilers  may  be  reduced  materially  in  size  and  cost,  compared 
with  those  required  by  the  high-pressure  form.  This  principle  of 
expansion  without  condensation  cannot  be  used  with  advantage 
where  the  steam  pressure  is  below  75  Ibs. 

35 


546 


HANDBOOK    ON    ENGINEERING. 


Fig.  278.    The  Deane  direct  acting  pump. 


Fig.  279.    Sectional  view  of  the  Deane  pamp. 
DEANE  DIRECT  ACTING  STEAM  PUMP. 

The  operation  of  the  steam  valves*  —  In    the    Deane   steam 
pump  a  rotary  motion    is    not    developed    by  means  of  which  an 


HANDBOOK    ON    ENGINEERING. 


547 


eccentric  can  be  made  to  operate  the  valve.  It  is,  therefore, 
necessary  to  reverse  the  piston  by  an  impulse  derived  from  itself 
at  the  end  of  each  stroke.  This  cannot  be  effected  in  an  ordinary 
single-valve  engine,  as  the  valve  would  be  moved  only  to  the  cen- 
ter of  its  motion,  and  then  the  whole  machine  would  stop.  To 
overcome  this  difficulty,  a  small  steam  piston  is  provided  to  move 
the  main  valve  of  the  engine.  In  the  Deane  steam  pump,  the 
lever  90,  which  is  carried  by  the  piston  rod,  comes  in  contact 


Fig.  280.    Showing  the  valves  properly  set. 


with  the  tappet  when  near  the  end  of  its  motion,  and  by  means 
of  the  valve-rod  24,  moves  the  small  slide-valve  which  operates 
the  supplemental  piston  9.  The  supplemental  piston,  carrying 
with  it  the  main  valve,  is  thus  driven  over  by  steam  and  the 
engine  reversed.  If,  however,  the  supplemental  piston  fails 
accidentally  to  be  moved,  or  to  be  moved  with  sufficient  prompt- 
ness by  steam,  the  lug  on  the  valve-rod  engages  with  it  and 
compels  its  motion  by  power  derived  from  the  main  engine. 


548 


HANDBOOK    ON    ENGINEERINGS 


Fig.  281.    Sectional  view  of  the  Cameron  pump. 

The  above  is  a  sectional  view  of  the  steam  end  of  a  Cameron 
pump. 

Explanation :  A  is  the  steam  cylinder  ;  (7,  the  piston  ;  Z>,  the 
piston  rod ;  L,  the  steam  chest;  F^  the  chest  piston  or  plunger, 
the  right-hand  end  of  which  is  shown  in  section ;  6r,  the  slide 
valve ;  H,  a  starting  bar  connected  with  a  handle  on  the  outside ; 
II  are  reversing  valves  ;  KK&YQ  the  bonnets  over  reversing  valve 
chambers ;  and  E  E  are  exhaust  ports  leading  from  the  ends  of 
steam  chest  direct  to  the  main  exhaust,  and  closed  by  the  revers- 
ing valve  //;  Nis  the  body  piece  connecting  the  steam  and  water 
cylinder. 


HANDBOOK    ON    ENGINEERING.  549 

Operation  of  the  Cameron  pump :  Steam  is  admitted  to  the 
steam  chest,  and  through  small  holes  in  the  ends  of  the  plunger ; 
F  fills  the  spaces  at  the  ends  and  the  ports  E  E  as  far  as  the 
reversing  valves  II;  with  the  plunger  F  and  slide  valve  G  in 
position  to  the  right  (as  shown  in  cut),  steam  would  be  admitted 
to  the  right-hand  end  of  the  steam  cylinder  A,  and  the  piston  C 
would  be  moved  to  the  left.  When  it  reaches  the  reversing  valve 
/  it  opens  it  and  exhausts  the  space  at  the  left-hand  end  of  the 
plunger  .F,  through  the  passage  E;  the  expansion  of  steam  at  the 
right-hand  end  changes  the  position  of  the  plunger  F,  and  with  it 
the  slide  valve  6r,  and  the  motion  of  the  piston  C  is  instantly 
reversed.  The  operation  repeated  makes  the  motion  continuous. 
In  its  movements,  the  plunger  F  acts  as  a  slide  valve  to  shut  off 
the  ports  E  E,  and  is  cushioned  on  the  confined  steam  between 
the  ports  and  steam  chest  cover.  The  reversing  valves  I  I  are 
closed  immediately  the  piston  C  leaves  them ,  by  pressure  of  steam 
on  their  outer  ends,  conveyed  direct  from  the  steam  chest. 

Operation*  —  Supposing  the  steam  piston  C  moving  from  right 
to  left:  When  it  reaches  the  reversing  valve  /  it  opens  it  and 
exhausts  the  space  on  the  left-hand  end  of  the  plunger  F,  through 
the  passage  E,  which  leads  to  the  exhaust  pipe ;  the  greater  pres- 
sure inside  of  the  steam  chest  changes  the  position  of  the  plunger 
F  and  slide  valve  6r,  and  the  motion  of  the  piston  C  is  instantly 
reversed.  The  same  operation  repeated  at  each  stroke  makes  the 
motion  continuous.  The  reversing  valves  //are  closed  by  a  pres- 
sure of  steam  on  their  large  ends,  conveyed  by  an  unseen  passage 
direct  from  the  steam  chest.  When  a  pump  is  first  connected, 
remove  the  bonnets  K  K  and  valves  1 1  and  blow  steam  through 
to  remove  any  dirt,  oil  or  gum  that  may  be  lodged  in  the  steam 
ports.  Take  valve  F,  valve  G  and  //out  and  wipe  off  with 
clean  waste,  and  then  oil  and  put  back.  Then  see  that  the  pack- 
ing is  not  too  tight.  When  a  Cameron  pump  has  been  run  a  long 
time,  the  plunger  F  becomes  worn  and  leaks  enough  steam  to 


550 


HANDBOOK    ON    ENGINEERING. 


cause  the  valve  F  to  become  balanced.  The  effect  of  this  is,  the 
pump  will  remain  on  the  end  ;  to- overcome  this,  take  out  plunger 
F,  or  piston,  as  it  is  called  by  some,  and  drill  the  little  hole  that 
you  will  find  in  the  ends  of  same  a  little  larger,  say  about  one- 
fourth  larger ;  that  will  increase  the  pressure  on  both  ends  of 
plunger  F;  as  soon  as  the  piston  comes  in  contact  with  valve  7 
the  steam  is  exhausted  to  exhaust  pipe. 


Fig.  282.    Sectional  view  of  the  Knowles  pump. 
THE  KNOWLES  DIRECT  ACTING  STEAH  PUMP. 

Explanation  of  steam  valves,  etc*  —  The  Knowles,  in  fact,  all 
first-class  direct  acting  steam  pumps,  are  absolutely  free  from  what 
is  termed  a  "  dead  center,"  when  in  first-class  order. 

This  feature  in  the  Knowles  pump  is  secured  by  a  very  simple 
and  ingenious  mechanical  arrangement,  i.  e.,  by  the  use  of  an 
auxiliary  piston,  which  works  in  the  steam  chest  and  drives  the 
main  valve.  This  auxiliary  or  tc  chest  piston,"  as  it  is  called,  is 
driven  backward  and  forward  by  the  pressure  of  steam,  carrying 


HANDBOOK    ON    ENGINEERING. 


551 


with  it  the  main  valve,  which  valve,  in  turn,  gives  steam  to  the 
main  steam  piston  that  operates  the  pump.  This  main  valve  is  a 
plain  slide  valve  of  the  B  form,  working  on  a  flat  seat.  The  chest 
piston  is  slightly  rotated  by  the  valve  motion  ;  this  rotative  move- 
ment places  the  small  steam  ports,  I),  E,  F  (which  are  located  in 


Fig.  283.     The  Kuowles  direct  acting  steam  pump. 

the  under  side  of  the  said  chest  pision) ,  in  proper  contact  with 
corresponding  ports  A  B  cut  in  the  steam  chest  No.  31.  The 
steam  entering  through  the  port  at  one  end  and  filling  the  space 
between  the  chest  piston  and  the  head,  drives  the  said  piston  to 
the  end  of  its  stroke  and,  as  before  mentioned,  carries  the  main 
slide  valve  with  it.  When  the  chest  piston  has  traveled  a  certain 
distance,  a  port  on  the  opposite  end  is  uncovered  and  steam  there 
enters,  stopping  its  further  travel  by  giving  it  the  necessary 


552 


HANDBOOK    ON    ENGINEERING. 


cushion.  In  other  words,  when  the  rotative  motion  is  given  to 
the  auxiliary  or  valve -driving  piston  by  the  mechanism  outside, 
it  opens  the  port  to  steam  admission  on  one  end,  and  at  the  same 
time  opens  the  port  on  the  other  end  to  the  exhaust. 


Fig.  284.     Showing  the  valves  properly  set. 


Operation  of  the  Knowles  pump  is  as  follows :  The  piston  rod, 
\vith  the  tappet  arm,  moves  backward  and  forward  from  the 
impulse  given  by  the  steam  piston.  At  the  lower  part  of  this 
tappet  arm  is  attached  a  stud  or  bolt,  on  which  there  is  a  friction 
roller.  This  roller  coming  in  contact  with  the  "  rocker  bar"  at 
the  end  of  each  stroke,  operates  the  latter.  The  motion  given  the 
44  rocker  bar  "  is  transmitted  to  the  valve  rod  by  means  of  the 
connection  between,  causing  the  valve  rod  to  partially  rotate. 
This  action,  as  mentioned  above,  operates  the  chest  piston,  which 
carries  with  it  the  main  slide  valve,  the  said  valve  giving  steam  to 
the  main  piston.  The  operation  of  the  pump  is  complete  and 


HANDBOOK    ON    ENGINEERING.  553 

continuous.  The  upper  end  of  the  tappet  arm  does  not  come  in 
contact  with  the  tappets  on  the  valve  rod,  unless  the  steam  pres- 
sure from  any  cause,  should  fail  to  move  the  chest  piston,  in  which 
case  the  tappet  arm  moves  it  mechanically. 

ADJUSTMENT  OF  THE  KNOWLES  PUMP. 

1.  Should  the  pump  run  longer  stroke  one  way  than  the  other, 
simply  lengthen  or  shorten  the  rocker  connection  (part  25)  so 
that  rocker  bar  (part  23)  will  touch  rocker  roller  (20)  equally 
distant  from  center  (22). 

2.  Should  a  pump  hesitate  in  making  its  return  stroke,  it  is  be- 
cause rocker  roller  (20)  is  too  low  and  does  not  come  in  contact 
with  the  rocker  bar  (23)  soon  enough.     To  raise  it,  take  out 
rocker  roller  stud  (20 A),  give  the  set  screw  in  this  stud  a  suffi- 
cient downward  turn,  and  the  stud  with  its  roller  may  at  once  be 
raised  to  proper  height. 

3.  Should  valve  rod   (17)  ever  have  a  tendency  to  tremble, 
slightly  tighten  up  the  valve  rod  stuffing  box  nut  (28) .     When 
the  valve  motion  is  properly  adjusted,  tappet  tip  (1 6)  should 
not  quite  touch   collar  (15)  and   clamp    (27).     Rocker  roller 
(20),  coming  in  contact  with  rocker  bar  (23)  will  reverse  the 
stroke. 

Operation  and  construction  of  the 

HOOKER  DIRECT  ACTING  STEAM=PUMP. 

The  parts  being  in  position,  as  shown,  the  steam  on  being  ad- 
mitted to  the  center  of  the  valve  chamber,  brings  its  pressure  to 
bear  on  the  main  and  supplemental  flat  slide  valve  4  and  7,  and 
also  within  the  recess  in  the  center  of  the  supplemental  piston  6. 
The  recess  incloses  the  main  valve  4,  so  that  this  valve  will  move 
with  the  supplemental  piston  whenever  the  steam  is  supplied  to 


554 


HANDBOOK    ON    ENGINEERING. 


and  exhausted  from  each  end  of  this  piston.  The  live  steam 
passes  through  the  left-hand  ports  A  l  Bl,  driving  the  main  piston 
2  to  the  right,  and  the  exhaust  passes  out  through  the  right-hand 
ports  A  and  C  under  the  cavity  in  the  main  valve  4  to  the  atmos- 
phere. As  the  main  piston  nears  the  right  hand  port,  the  valve 
lever  15,  which  is  attached  to  the  piston  rod  3,  brings  the  dog  17, 
in  plate  16,  in  contact  with  the  valve  arm  15,  and  moves  the  sup- 
plemental valve  7  to  the  right,  thus  supplying  live  steam  to  the 


Fig.  285.    Plan  and  sectional  views  of  Hooker  pnmp. 

right  of  the  supplemental  piston  6',  and  exhausting  from  the  left 
through  the  ports  e  e.  As  the  supplemental  piston  incloses  the 
main  valve,  this  valve  is  carried  with  it  to  the  left.  Steam  now 
enters  the  right-hand  ports  A  B  and  is  exhausted  from  the  left- 
hand  main  port  A.  The  engine  commences  its  return  stroke  and 
the  operation  just  described  becomes  continuous.  As  the  main 
piston  (2)  closes  the  main  port  (A)  to  the  right,  it  is  arrested  on 
compressed  exhaust  steam.  The  main  valve  4  having  closed  the 
auxiliary  ports  (_B)  leading  to  that  end  of  the  main  cylinder,  the 


HANDBOOK   ON   ENGINEERING. 


555 


Fig.  286.     Showing  the  steam  valves  properly  set. 

etearn  being   supplied  through  both  the  main  and  auxiliary  ports, 
but  released  through  the  main  ports  only. 


BLAKE  STEAM  PUHP. 

Description  of  the  Blake  steam  pump.  —  The  Blake  steam 
pump  is  absolutely  positive  in  its  action ;  that  is  to  say,  the 
operation  at  the  slowest  speed  under  any  pressure,  is  perfectly 
continuous,  and  the  pump  is  never  liable  to  stop  as  the  main  valve 
passes  its  center,  if  the  pump  is  in  good  order.  An  ingenious  and 
simple  arrangement  is  used  in  the  Blake  pump  to  overcome  the 
'•'  dead  center,"  as  will  be  seen  from  the  engraving,  Fig.  288. 

Operation  of  the  Blake  steam  pump.  —The  main  or  pump 
driving  piston  A  could  not  be  made  to  work  slowly  were  the 
valve  to  derive  its  movement  soJely  from  this  piston ;  for 


556 


HANDBOOK    ON    ENGINEERING. 


when  this  valve  had  reached    the  center  of   its  stroke,  in    which 
position  the  ports  leading  to  the  main  cylinder  would  be  closed, 


Fig.  287.     The  Blake  steam  pump. 

no  steam  could  enter  the  cylinder  to  act  on  said  piston,  con- 
sequently, the  latter  would  come  to  rest,  since  its  momentum 
would  be  insufficient  to  keep  it  in  motion,  and  the  main 
valve  would  remain  in  its  central  position  or  tc  dead  cen- 
ter." To  shift  this  valve  from  its  central  position  and 
admit  steam  in  front  of  the  main  piston  (whereby  the  motion 
of  the  piston  is  reversed  and  its  action  continued),  some  agent 
independent  of  the  main  piston  must  be  used.  In  the  Blake 
pump,  this  independent  agent  is  the  supplemental  or  valve-driving 
piston  B.  The  main  valve,  which  controls  the  admission  of  steam 
to.  and  the  escape  of  steam  from,  the  main  cylinder,  is  divided 
into  two  parts,  one  of  which,  (7,  slides  upon  a  seat  on  the  main 
cylinder,  and,  at  the  same  time,  affords  a  seat  for  the  other  part, 


HANDBOOK   ON   ENGINEERING . 


557 


Z>,  which  slides  upon  the  upper  face  of  C.  As  shown  in  the  en- 
graving, D  is  at  the  left-hand  end  of  its  stroke,  and  C  at  the 
opposite,  or  right-hand  end  of  its  stroke.  Steam  from  the  steam- 
chest  J  is,  therefore,  entering  the  right-hand  end  of  the  main 
cylinder  through  the  ports  E  and  H,  and  the  exhaust  is  escap- 
ing through  the  ports  Hl  and  H71,  K  and  M,  which  causes  the 


Fig.  288.    Sectional  views   of  steam  cylinder,  valves,  etc.,  of  the 
Blake  steam  pump. 

main  piston  A  to  move  from  right  to  left.     When  this  piston  has 
nearly  reached  the  left-hand  end  of  its  cylinder  the  valve  motion 


558 


HANDBOOK    ON    ENGINEERING. 


(not  shown)  moves  the  valve-rod  P,  and  this  causes  (7,  together 
with  its  supplemental  valve  R  and  S  Sl  (which  form,  with  (7,  one 
casting)  to  be  moved  from  right  to  left.  This  movement  causes 
steam  to  be  admitted  to  the  left-hand  end  of  the  supplemental 
cylinder,  whereby  its  piston  B  will  be  forced  toward  the  right, 
carrying  D  with  it  to  the  opposite  or  right-hand  end  of  its  stroke ; 
for  the  movement  of  S  closes  N  (the  steam  port  leading  to  the 


Fig.  289.    Showing  the  valves  properly  set, 

right-hand  end),  and  the  movement  of  S1  opens  N1  (the  port 
leading  to  the  opposite,  or  left-hand  end).  At  the  same  time  the 
movement  of  0  opens  the  right-hand  end  of  the  cylinder  to 
the  exhaust  through  the  exhaust  ports  X  and  Z.  The  ports  C 
and  D  now  have  positions  opposite  to  those  shown  in  the  engrav- 
ings, and  steam  is,  therefore,  entering  the  main  cylinder  through 
the  ports  El  and  Hl,  and  escaping  through  the  ports  H,  E,  K 
and  Jf,  which  will  cause  the  main  piston  A  to  move  in  the  op- 


HANDBOOK    ON    ENGINEERING.  559 

posite  direction,  or  from  left  to  right,  and  operations  similar  to 
those  already  described  will  follow,  when  the  piston  approachee 
the  right-hand  end  of  its  cylinder.  By  this  simple  arrangement 
the  pump  is  rendered  positive  in  its  action  ;  that  is,  it  will  in- 
stantly start  and  continue  working  the  moment  steam  is  admitted 
to  the  steam  chest.  The  main  piston  A  cannot  strike  the  head  of 
the  cylinder,  for  the  main  valve  has  a  lead ;  or,  in  other  words, 
steam  is  always  admitted  in  front  of  said  piston  just  before  it 
reaches  either  end  of  its  cylinder,  even  should  the  supplemental 
piston  B  be  tardy  in  its  action  and  remain  with  D  at  that  end, 
toward  which  the  piston  A  is  moving ;  for  C  would  be  moved  far 
enough  to  open  the  steam  port  leading  to  the  main  cylinder,  since 
the  possible  travel  of  C  is  greater  than  that  of  D.  The  supple- 
mental piston  B  cannot  strike  the  heads  of  its  cylinders,  for  in  its 
alternate  passage  beyond  the  exhaust  ports  X  and  X,  it  cushions 
on  the  vapor  intrapped  in  the  ends  of  this  cylinder. 

MISCELLANEOUS  PUHP  QUESTIONS. 

Q.  What  is  a  pump?  A.  It  is  hard  to  get  a  definition  that 
will  cover  the  whole  ground.  A  pump  may  be  said  to  be  a 
mechanical  contrivance  for  raising  or  transferring  fluids  ;  and  as  a 
general  thing  consists  of  a  moving  piece  working  in  a  cylinder  or 
other  cavity ;  the  device  having  valves  for  admitting  or  retaining 
the  fluids. 

Q.  What  two  classes  of  operations  are  included  in  the  term 
"raising"  fluids?  A.  They  may  be  raised  by  drafting  or  suc- 
tion, from  their  level  to  that  of  the  pump ;  they  may  be  raised 
from  the  level  of  the  pump  to  a  higher  level. 

Q.  Do  pumps  always  "raise"  by  either  method,  from  one 
level  to  a  higher  one,  the  liquid  which  they  transfer?  A.  No  ;  in 
many  cases  the  liquid  flows  by  gravity  to  the  pump  ;  and  in  some 
it  is  delivered  at  a  lower  level  than  that  at  which  it  is  received. 


560  HANDBOOK    ON    ENGINEERING  0 

Q.  Where  a  pump  is  not  used  for  raising  a  liquid  to  a  higher 
level,  for  what  is  it  generally  used  ?  A.  To  increase  or  decrease 
its  pressure. 

Q.  What  classes  of  Liquids  are  handled  by  pumps  ?  A.  Air, 
ammonia,  lighting  gas,  oxygen,  etc. 

Q.  Name  some  liquids  which  are  handled  by  pumps?  A. 
Water,  brine,  beer,  tan  liquor,  molasses,  acids  and  oils. 

Q.  Where  it  is  not  specified  whether  a  pump  is  for  gas  or  for 
liquid,  which  is  generally  understood?  A.  Liquid. 

Q.  What  gas  is  most  frequently  pumped?     A.  Air. 

Q.  What  liquid  is  generally  understood  if  none  other  is  speci- 
fied for  a  pump?  A.  Water. 

Q.  Can  pumps  handle  hot  and  cold  liquids?  A.  Yes;  though 
cold  are  easier  handled  than  hot. 

Q.  What  is  the  difference  between  a  fluid  and  a  liquid?  A. 
Every  liquid  is  a  fluid  ;  every  fluid  is  not  a  liquid.  Air  is  a  fluid  ; 
water  is  both  a  fluid  and  a  liquid.  Every  liquid  can  be  poured 
from  one  vessel  to  another. 

SUCTION. 

Q.  What  causes  the  water  to  rise  in  a  pump  by  so-called 
suction?  A.  The  unbalanced  pressure  of  the  air  upon  the  surface 
of  the  liquid  below  the  pump,  forces  the  water  up  into  the  suction 
pipe  when  the  piston  is  withdrawn  from  the  liquid. 

Q.  How  much  is  the  pressure  of  the  atmosphere?  A.  At  the 
sea  level  about  14.71bs.  per  square  inch,  or  2116.8  Ibs.  per  square 
foot. 

Q.  In  what  direction  is  this  pressure  exerted?  A.  In  every 
direction  equally. 

Q.  What  tends  to  prevent  the  water  from  being  lifted?  A. 
The  force  of  gravity,  which  is  the  result  of  the  attraction  of  the 
earth. 


HANDBOOK    ON    ENGINEERING.  56'1 

Q.  In  what  direction  does  the  force  of  gravity  act?  A.  In 
radial  lines  towards  the  center  of  the  earth. 

Q.  With  what  force  does  this  gravity  act?  A.  That- depends 
upon  the  substance  upon  which  it  is  acting. 

Q.  Why  do  you  refer  to  the  level  of  the  sea  in  speaking  of  the 
pressure  of  the  air  and  the  weight  of  water?  A.  Because  the  air 
pressure  becomes  less  as,  in  rising  above  the  sea  level,  we  recede 
from  the  center  of  the  earth,  and  the  weight  of  a  given  quantity 
of  water  or  any  other  substance  becomes  less  than  it  is  at  the  level 
of  the  sea,  as  we  approach  to  or  recede  from  the  center  of  the 
earth. 

Q.  How  is  it  that  the  weight  of  any  substance  becomes  less  if 
you  go  either  above  or  below  the  sea  level?  A.  The  farther  you 
go  from  the  earth,  the  less  its  attraction  and  the  less  a  given 
body  will  weigh  upon  a  spring  balance.  The  farther  down  into 
the  earth  you  go,  the  nearer  you  get  to  the  center  of  the  earth,  at 
which,  there  being  attraction  upon  all  sides,  any  body  would 
weigh  nothing.  Going  from  the  surface  of  the  earth  towards  its 
center,  then,  a  body  weighs  less  and  less  upon  a  spring  balance. 

Q.  Why  do  you  specify  a  spring  balance?  A.  Because  in 
weighing  by  counterpoise,  both  the  body  to  be  weighed  and  the 
counterpoise  by  which  it  is  weighed,  would  change  their  weights 
in  the  same  proportion,  as  the  position  with  regard  to  the  center 
of  the  earth  was  changed. 

Q.  What  are  the  causes  which  principally  prevent  pumps  from 
lifting  up  to  the  normal  maximum?  A.  Friction  ;  leakage  of  air 
into  the  suction,  chokes  in  the  suction  pipe. 

Q.  Can  a  liquid  be  "  drafted"  without  the  expenditure  of 
work  ?  A.  No ;  in  drafting  a  liquid  to  the  full  height  to  which  it 
can  be  drafted,  at  least  as  much  power  must  be  expended  as 
would  lift  the  same  weight  of  liquid  that  height  by  any  mechan- 
ical means  ;  only  the  amounts  of  friction  being  different. 

Q.  Then  what  advantage  is  there  in  having  a  pump  draft  its 

36 


562  HANDBOOK    ON    ENGINEERING. 

water  to  the  full  possible  height,  over  having  it  force  the  watei 
the  full  height?  A.  Convenience  in  having  the  pump  higher  up. 

Q.  Can  a  pump  throw  water  higher  or  farther,  with  a  given 
expenditure  of  power,  where  it  flows  in,  than  where  it  must  draft 
its  water?  A.  Yes;  on  the  same  principle  that  it  can  throw 
farther  or  force  harder  when  the  water  is  forced  to  its  suction 
side  than  where  it  merely  flows  in. 

Q.  What  is  the  use  of  the  suction  chamber?  A.  To  enable 
the  pump  barrel  to  fill  where  the  speed  is  high ;  to  prevent 
pounding,  when  the  pump  reverses. 

Q.  Upon  what  does  the  lifting  capacity  of  a  pump  depend? 
A.  When  the  pump  is  in  good  order  its  lifting  capacity  depends 
mainly  upon  the  proportion  of  clearance  in  the  cylinder  and  valve 
chamber  to  the  displacement  of  the  piston  and  plunger. 

Q.  Which  will  lift  farther,  an  ordinary  piston  pattern  pump  or 
a  plunger  pump?  And  why?  A.  Other  things  being  as  nearly 
equal  as  they  can  be  made  between  these  two  pumps,  the  piston 
pump  will  lift  the  farther  of  the  two,  because  the  plunger  pump 
has  the  most  clearance. 

Q.  What  is  the  advantage  of  the  suction  chamber?  A.  To 
assist  the  pump  in  drafting,  especially  at  high  speed. 

Q.  What  is  the  advantage  of  the  air  chamber?  A.  To  make 
the  stream  steady. 

Q.  What  difficulty  is  sometimes  met  with  in  using  an  air 
chamber?  A.  Where  the  pressure  is  very  great  sometimes  the 
air  is  absorbed  by  the  water,  and  thus  the  cushion  is  detroyed. 

FORCING. 

Q.  What  will  be  the  volume  of  the  air  in  the  air  chamber  of  a 
force  pump,  when  the  pump  is  forcing  against  a  head  of  67.6 
feet?  A.  It  will  be  reduced  to  half  its  ordinary  volume,  because 
it  will  be  at  the  pressure  of  two  atmospheres. 


HANDBOOK    ON    ENGINEERING. 


563 


Fig.  290.    Pump  cylinder  fitted  with  liner. 

The  above  cut  shows  a  pump  with  a  removable  cylinder 
or  liner,  and  is  packed  with  fibrous  packing  set  out  by  adjustable 
set  screws  and  nuts.  This  style  of  a  pump  is  the  best  for  small 
water-works  or  elevators,  or  where  a  pump  is  used  where  the 
water  is  muddy  or  sandy. 

To  find  the  horse  power  necessary  to  elevate  water  to  a 
given  height:  Multiply  the  total  weight  of  the  water  in  pounds 
by  the  height  in  feet  and  divide  the  product  by  33,000  (an  allow- 
ance of  25  per  cent  should  be  added  for  water  friction,  and  a  further 
allowance  of  25  per  cent  for  loss  in  steam  cylinder.) 

The  heights  to  which  pumps  will  force  water  when  running  at 


564  HANDBOOK    ON    ENGINEERING. 

100  feet  piston  speed  per  minute,  and  the  suction  and  discharge 
pipes  being  of  moderate  length,  will  be  found  by  dividing  the  area 
of  the  steam  piston  by  the  area  of  the  water  piston,  and  multi- 
plying the  quotient  by  the  steam  pressure.  Deduct  40  per  cent 
for  friction  and  divide  the  remainder  by  .434. 

Example*  —  To  what  height  will  an  8-inch  steam  piston,  with 
a  5-inch  water  piston,  force  water,  the  steam  pressure  being  80 
Ibs.  by  gauge?  Ans.  283  ft.  nearly. 

Operation*  —  Area  of  steam  piston  =  50.  26  sq0  ins. 
"      "  water      "       =19.63   "     " 

Then,  ^^  =  2.56.     And  2.56  X  80  =  204.80  Ibs. 
19.63 

Then,  204.80  less  40%  =    122.88  Ibs. 
And,  122f8  =  283  +  feet. 


An  allowance  must  be  made  where  long  pipes  are  used. 

The  normal  speed  of  pumps  is  taken  at  100  piston  feet  per 
Jninute,  which  speed  can  be  considerably  increased  if  desired. 

For  feeding*  boilers,  a  speed  of  25  to  50  lineal  feet  per  minute 
is  most  desirable. 

A  gallon  of  water,  U.  S.  Standard,  weighs  8^  Ibs.  and  contains 
231  cubic  inches. 

A  cubic  foot  of  water  weighs  62.425  Ibs.  and  contains  1,728 
cubic  inches,  or  7J  gallons. 

Doubling  the  diameter  of  a  pipe  increases  its  capacity  four 
times. 

Friction  of  liquids  in  pipes  increases  as  the  square  of  the 
velocity. 

To  find  the  area  of  a  piston,  square  the  diameter  and  multiply 
by  ,7854. 


HANDBOOK    ON    ENGINEERING.  565 

Boilers  require,  for  each  nominal  horse-power,  about  one  cubic 
foot  of  feed  water  per  hour. 

In  calculating*  horse  power  of  tubular  or  flue  boilers,  consider 
15  square  feet  of  heating  surface  equivalent  to  one  nominal  horse- 
power. 

To  find  the  pressure  in  pounds  per  square  inch  of  a  column 
of  water,  multiply  the  height  of  a  column  in  feet  by  .434. 
Approximately,  we  say  that  every  foot  of  elevation  is  equal  to 
one-half  Ib.  pressure  per  square  inch ;  this  allows  for  ordinary 
friction. 

The  area  of  the  steam  piston,  multiplied  by  the  steam  pressure, 
gives  the  total  amount  of  pressure  that  can  be  exerted.  The 
area  of  the  water  piston,  multiplied  by  the  pressure  of  water  per 
square  inch,  gives  the  resistance.  A  margin  must  be  made 
between  the  power  and  the  resistance  to  move  the  pistons  at  the 
required  speed  —  say  from  20  to  40  per  cent,  according  to  speed 
and  other  conditions. 

To  find  the  capacity  of  a  cylinder  in  gallons :  Multiplying  the 
area  in  inches  by  the  length  of  stroke  in  inches  will  give  the  total 
number  of  cubic  inches  ;  divide  this  amount  by  231  (which  is  the 
cubical  contents  of  a  gallon  of  water)  and  quotient  is  the  capacity 
in  gallons. 

To  find  quantity  of  water  elevated  in  one  minute  running  at  100 
feet  of  piston  speed  per  minute :  Square  the  diameter  of  water 
cylinder  in  inches  and  multiply  by  4. 

Example:  Capacity  of  a  five-inch  cylinder  is  desired.  The 
square  of  the  diameter  (5  inches)  is  25,  which,  multiplied  by  4, 
gives  100,  which  is  gallons  per  minute,  approximately. 

Q.  What  is  the  reason  that  a  steam  pump  of  the  horizontal 
double  acting  type  should  throw  an  intermitting  stream  under 
pressure,  like  the  stream  from  milking  .a  cow,  only  not  quite  so 
bad  as  that?  Have  tried  valves  of  different  sizes,  with  different 
amount  of  rise,  springs  or  valves  of  different  tension,  different 


066  HANDBOOK    ON    ENGINEERING. 

. 
kinds  of  packing  in  water  piston,  and  different  sized  water  ports 

or  passages,  without  any  apparent  difference.  A.  Steam  pumps 
of  the  horizontal  double-acting  type  are  not  alone  in  throwing  an 
Intermitting  stream.  The  same  thing  shows  up  in  vertical  single- 
acting  pumps  ;  but  all  horizontal  double-acting  pumps  do  not  so 
behave.  The  steam  fire  engine  shows  that  no  type  of  pump  is 
exempt  from  ;t  squirting." 

Q.  How  may   this  squirting   be  lessened?     A.  By  increasing 
the  suction    valve    area ;   by  giving   more  suction   chamber  and 
more  air  chamber. 
********* 

Q.  What  is  a  sinking  pump  ?  A.  One  which  can  be  raised  and 
lowered  conveniently,  for  pumping  out  drowned  mines,  etc. 

Q ,  Into  what  main  general  classes  may  reciprocating  cylinder 
pnmps  be  divided?  A.  Into  single  acting  and  double  acting. 

Q.  What  is  a  single  acting  reciprocating  pump  ?  A.  One  in 
which  each  reciprocation  or  single  stroke  in  one  direction  causes 
one  influx  of  fluid,  and  each  reciprocation  or  single  stroke  in  the 
opposite  direction  causes  one  discharge  of  fluid.  In  other  words, 
the  pump,  as  regards  its  action,  is  single  ended. 

Q.  What  is  a  double  acting  reciprocating  pump  ?  A.  One  in 
which  each  end  acts  alternately  for  suction  and  discharge.  Re- 
ciprocation of  the  piston  in  one  direction  causes  an  influx  of 
fluid  into  one  end  of  the  pump  from  the  source,  and  a  discharge 
of  fluid  at  the  opposite  end ;  on  the  return  stroke  the  former 
suction  end  becomes  the  discharge  end.  In  other  words,  the 
pump  is  double  ended  in  its  action  ;  or  is  "  double-acting." 

Q.  What  is  the  special  advantage  of  having  double-acting 
pump  cylinders?  A.  The  column  of  water  is  kept  in  motion 
more  constantly,  and  hence  there  is  less  jar ;  smaller  pipes  may 

be  u«ed. 

*********** 

Q.  How  may  those  pumps  which  are  driven  by  steam  against  a 


HANDBOOK    ON    ENGINEERING.  567 

steam  piston  be  divided?  A.  Into  those  which  have  a  fly  wheel 
and  those  which  have  no  fly  wheel. 

Q.  Into  what  classes  may  those  pumps  which  are  driven  by 
steam,  without  a  flywheel,  be  divided?  A.  Into  direct  acting 
and  duplex. 

Q.  What  is  the  advantage  of  a  fly  wheel  steam  pump?  A. 
Steadiness  of  action ;  the  capability  of  using  the  steam  expan- 
sively. 

Q.  What  are  the  disadvantages  of  fly  wheel  pumps?  A.  Great 
weight ;  inability  to  run  them  very  slowly  without  gearing  down 
from  the  fly  wheel  shaft,  as  the  wheel  must  run  comparatively 
rapidly. 

Q.  What  is  a  direct-acting  steam  pump?  A.  One  in  which 
there  is  no  rotary  motion,  the  piston  being  reversed  by  an  impulse 
derived  from  itself  at  or  near  the  end  of  each  stroke.  There  is 
but  one  steam  cylinder  for  one  water  cylinder ;  the  valve  motion 
of  the  steam  cylinder  being  controlled  by  the  action  of  the  steam 
in  that  cylinder. 

HOW  TO  SET  THE  STEAfl  VALVES  ON  A  DUPLEX  PUMP. 

The  steam  valves  on  duplex  pumps  generally  have  no  outside 
lap,  consequently,  in  their  central  position,  they  just  cover  the 
steam  ports  leading  to  the  opposite  ends  of  cylinder. 

By  lost  motion  is  meant,  the  distance  a  valve-rod  travels 
before  moving  the  valve;  if  the  steam-chest  cover  is  off  the 
amount  of  lost  motion  is  shown  by  the  distance  the  valve  can  be 
moved  back  and  forth  before  coming  in  contact  with  the  valve- 
rod  nut.  The  object  of  lost  motion  is  to  allow  one  pump  to 
almost  complete  its  stroke  before  moving  the  valve  of  its  fellow 
engine.  As  the  steam  piston  is  nearing  the  end  of  its  stroke,  it 
moves  the  valve  of  its  fellow  engine,  admitting  steam  and  start- 
ing its  fellow  engine  as  it  lays  down  its  own  work ;  in  other  words, 


568 


HANDBOOK    ON    ENGINEERING. 


the  other  picks  it  up.  The  amount  of  lost  motion  required  is 
enough  to  allow  each  piston  to  complete  its  stroke ;  in  other  words, 
if  there  was  no  lost  motion,  as  the  pistons  would  pass  the 
center  of  their  travel,  they  would  move  the  valve  of  theii 
fellow  engine,  and  the  result  would  be  a  very  short  stroke. 


Fig.  291.    Showing  the  steam  valves  properly  set. 

To  set  the  steam  valves,  move  the  steam  piston  towards  the 
steam  cylinder  head  until  it  comes  in  contact  with  the  head  ;  mark 
with  a  scribe  on  the  piston-rod  at  the  face  of  the  stuffing-box 
follower  on  steam  end  ;  then  move  the  piston  to  its  contact  stroke 
on  the  opposite  end  and  make  another  mark  on  the  piston-rod, 
exactly  half  way  between  the  face  of  the  stuffing-box  follower  on 
the  steam  end,  and  the  first  mark.  Then  move  the  piston  back 
until  the  middle  mark  is  at  the  face  of  piston-rod  stuffing-box 
follower  on  the  pump  end.  This  operation  brings  the  piston 
exactly  in  the  middle  of  the  stroke.  Then  take  off  the  steam 


HANDBOOK    ON   ENGINEERING.  569 

chest  cover,  place  the  slide-valve  in  the  center,  exactly  over  the 
steam  ports.  Place  the  slide-valve  nut  in  exact  center  between 
the  jaws  of  the  slide-valve,  screw  the  valve-rod  through  the  nut 
until  the  eye  on  the  valve-rod  head  comes  in  line  with  the  eye  of 
the  valve-rod  link  ;  slip  the  valve-rod  head  pin  through  head  and 
the  valve  is  set.  Repeat  the  same  operation  on  the  other  side  of 
the  pump.  Where  a  pump  is  fitted  with  four  hexagon  valve-rod 
nuts,  two  either  end  of  the  slide-valve,  instead  of  one  nut  in  the 
center  of  the  valve,  set  and  lock  these  hexagon  nuts  at  equal  dis- 
tances from  the  outer  end  of  the  slide-valve  jaws,  allowing  a  little 
lost  motion,  varying  from  J"  on  high-pressure  pumps,  to,  say, 
i"  on  low  service  pumps,  on  each  side  of  valve ;  if  the  steam 
piston  hits  the  head,  take  up  some  of  the  lost  motion ;  if  the 
steam  piston  should  not  make  a  full  stroke,  give  more  lost  motion. 

PROPER  MANNER  OF  ARRANGING  PIPE  CONNECTIONS. 

For  trie  purpose  of  showing  good  arrangement,  the  following 
cut  is  presented,  Fig.  292. 

On  long  lifts  it  is  necessary  to  provide  the  suction  pipe  S 
with  a  foot-valve  F.  By  the  use  of  a  foot-valve,  the  pipe  and 
cylinders  are  constantly  kept  charged  with  water,  allowing  the 
pump  to  start  without  having  to  free  itself  and  the  suction  pipe 
of  air.  In  case  of  a  long  lift,  the  vacuum  chamber  V  is  also 
essential.  This  may  be  readily  constructed  by  using  a  tee  in  place 
of  the  elbow  E,  extending  the  suction  pipe  and  placing  a  cap 
upon  the  top.  In  order  to  keep  the  water  back  when  the  pump  is 
being  examined  or  repaired,  a  gate  valve  should  be  placed  in  the 
delivery  pipe.  It  sometimes  happens  that,  either  purposely  or 
through  a  leak  in  the  foot-valve,  the  suction  chamber  becomes 
empty.  For  the  purpose  of  charging  the  suction  pipe  and  cylin- 
der a  "  charging  pipe  "  P  is  placed  outside  the  check  valve, 
connecting  the  delivery  pipe  D  with  the  suction.  In  order  that 


570 


HANDBOOK    ON    ENGINEERING. 


the  pump,  in  starting,  may  free  itself  of  air,  a  check  valve  Cand 
a  "  starting   pipe"  A  should   be  provided.     This  pipe  may  be 


Fig.  292.    Proper  arrangement  of  pipe  connections. 

led  to  any  convenient  place  of  discharge.  After  the  pump  has 
started,  the  valve  in  the  starting  pipe  should  be  closed  gradually. 
Faulty  connections  are  generally  the  cause  of  the  improper  action 


HANDBOOK    ON    ENGINEERING.  571 

of  a  pump.  Great  care  should,  therefore,  be  taken  to  have 
everything  right  before  starting.  A  very  small  leak  in  the  suc- 
tion will  cause  a  pump  to  work  badly. 

Q.  What  is  the  peculiarity  of  the  duplex  type?  A.  There  are 
two  steam  cylinders  and  two  water  cylinders ;  the  piston  of  one  of 
these  cylinders  works  the  valve  of  the  other  cylinder,  and  vice  versa. 
Neither  half  can  work  alone.  This  name  is  entirely  arbitrary. 

Q.  What  would  you  call  a  pumping  machine  in  which  there  are 
two  steam  cylinders,  each  operating  a  water  cylinder  in  line  with 
it ;  each  half  being  a  perfect  pumping  machine  independent  of  the 
other  side?  A.  A  "  double  "  pump. 

Q.  Can  a  direct  acting  steam  pump  use  steam  expansively? 
A.  Not  to  any  extent ;  in  fact,  there  would  be  danger  of  sticking 
upon  the  centers  in  most  cases,  if  there  was  lap  and  expansion. 

Q.  What  is  the  reason  that  a  single  cylinder  engine  cannot  well 
reverse  itself  without  a  fly  wheel,  by  means  of  the  ordinary  single 
D  valve?  A.  Because  when  the  valve  was  at  mid-travel,  both 
ports  of  the  valve  seat  would  be  closed  by  the  valva  faces,  and 
neither  exhaust  nor  admission  take  place. 

Q.  What  means  are  employed  in  a  direct  acting  steam  pump  to 
move  the  valve  ?  A.  A  small  supplementary  piston  is  used ;  this 
supplementary  piston  being  actuated  by  the  main  piston  in  any 
one  of  several  different  ways. 

Q.  What  are  the  principal  ways  of  working  the  supplementary 
piston  from  the  main  piston?  A.  (1)  The  main  piston  strikes 
the  tappet  of  a  small  valve,  which  opens  an  exhaust  passage  in 
one  end  of  the  cylinder,  containing  a  supplementary  piston,  and 
having  live  steam  pressing  upon  both  ends  of  the  supplementary 
piston  ;  (2)  by  the  main  piston  striking  a  rod  passing  through 
the  cylinder  head,  and  moving  a  lever,  which  controls  the  motion 
of  the  part  of  the  main  valve  to  which  is  attached  the  valves  which 
moves  the  supplementary  piston  ;  (3)  the  main  piston  rod  carries 
a  tappet  arm,  which  twists  the  stem  of  the  supplementary  piston, 


572  HANDBOOK    ON    ENGINEERING. 

thus  uncovering  ports  which  cause  its  motion ;  (4)  a  projection 
upon  the  main  piston  rod  engages  the  stem  and  operates  the  valve 
which  moves  the  supplementary  piston,  but  if  that  valve  should 
not,  by  means  of  its  steam  passages,  cause  quick  enough  or  sure 
enough  motion  of  the  supplementary  piston,  a  lug  upon  this  stem 
moves  the  supplementary  piston. 

Q.  In  the  first  of  these  four  classes,  what  is  the  principal 
element  in  the  valve  motion?  A.  A  difference  in  area  between 
the  eduction  port  of  the  supplemental  piston  and  its  induction  port 

Q.  What  is  the  principal  feature  in  the  second  class?  A.  A 
regular  slide  valve  letting  steam  upon  alternate  ends  of  the  sup- 
plemental piston. 

Q.  In  the  third  class,  what  is  the  main  feature?  A.  A  twist- 
ing motion  in  the  supplemental  piston. 

Q.  In  the  fourth  class,  what  is  the  principal  feature?  A. 
Movement  of  the  supplemental  piston  by  steam  controlled  by  a 
slide  valve,  and  by  the  mechanical  action  of  the  slide  valve  itself 
if  its  steam  distribution  is  defective. 

Q.  What  are  the  objections  to  most  pumps  of  the  direct  actiig 
type?  A.  The  unbalanced  condition  of  the  auxiliary  pistons  in 
the  exhaust  side,  causing  a  loss  of  steam  when  the  parts  are  worn, 
the  choking  up  of  the  small  ports  for  the  auxiliary  pistons,  by  the 
gumming  and  caking  of  the  oil  therein. 

Q.  Can  the  ordinary  direct  acting  steam  pump  use  steam 
expansively?  A.  No. 

Q.  How  may  this  be  done?     A.  Ity  compounding. 

Q.  What  is  to  be  taken  into  consideration  in  the  use  of  com- 
pound steam  pumps?  A.  That  they  are  designed  for  a  certain 
range  of  pressure  —  say  from  80  to  120  pounds  boiler  pressure, 
and  will  do  their  best  work  between  these  pressures. 

Q.  Have  all  direct  acting  steam  pumps  intermittent  valve 
motion  ?  A.  No ;  there  are  some  which  have  continuous  valve 
motion. 


HANDBOOK    ON    ENGINEERING.  573 

Q.  In  most  direct-acting  steam  pumps,  are  the  auxiliary  piston 
heads  made  together  or  in  separate  pieces  ?  A.  Together. 

Q.  They  are  in  contact  with  the  steam  in  the  chest?     A.  Yes. 

Q.  What  should  be  said  about  the  location  of  a  pump?  A.  It 
should  be  as  near  the  source  of  supply  as  is  convenient. 

Q.  What  may  be  said  about  convenience  in  repairs?  A.  The 
pump  should  have  room  left  upon  all  sides ;  and  upon  both  ends 
equal  to  its  length,  for  the  removal  of  the  piston  rods  in  case  of 
repairs. 

Q.  If  the  floor  is  not  strong  enough,  how  may  a  good  founda- 
tion be  made  ?  A.  By  digging  two  or  three  feet  into  the  ground 
and  building  up  the  proper  height  with  stone  or  brick  laid  in 
strong  cement,  with  a  cap  stone. 

Q.  What  may  be  said  about  suction  pipes?  A.  They  must  be 
as  large  as  possible ;  the  longer  they  are  the  greater  in  diameter 
they  should  be ;  they  should  be  as  straight  as  possible,  and  as 
free  from  bends  and  valves  ;  they  must  be  air-tight ;  they  must 
not  bo  allowed  to  get  obstructed  by  foreign  substances. 

Q.  W hat  may  be  said  about  the  area  of  strainer  holes?  A. 
They  should  have  an  aggregate  area  about  five  times  that  of  the 
suction  pipe. 

Q.  Where  are  foot  valves  necessary  ?  A.  Upon  long  suctions 
or  high  lifts. 

Q.  Should  two  pumps  take  their  suction  from  one  pipe  ?  A.  It 
should  be  avoided,  unless  the  pipe  is  very  large  ;  and  in  case  both 
suctions  should  be  arranged  so  that  one  of  the  pumps  should  not 
have  to  draft  at  right-angles  to  the  flow  of  water  going  to  the  other 
pump. 

Q.  What  arrangement  should  be  made  where  it  is  necessary  to 
have  two  pumps  draft  from  one  suction?  A.  There  should  be  a 
Y  connection. 

Q.  What  is  a  good  way  to  reduce  the  friction  in  suction  pipes 
where  there  are  many  bends  ?  A.  To  use  bends  of  wrought- 


574  HANDBOOK    ON    ENGINEERING. 

iron  pipe  of  as  long  a  radius  as  possible,  instead  of   oast-iron 
elbows. 

Q.  What  may  be  said  about  the  lower  end  of  the  suction  pipe? 
A.  It  should  generally  have  a  strainer ;  and  if  the  lift  is  over  12 
to  15  feet,  should  have  a  foot  valve. 

Q.  What  is  a  good  thing  to  do  with  the  discharge  pipe  near 
the  pump?  A.  To  put  a  valve  in  it  near  the  pump,  to  keep 
the  water  in  the  pipe  when  the  water  end  is  to  be  opened  for 
inspection  or  repairs. 

Q.  What  provision  should  be  made  for  priming  the  pump?  A. 
There  should  be  a  pipe  with  a  stop  valve  in  it  connected  from  the 
discharge  pipe  beyond  this  check  valve,  or  from  some  other  source 
of  supply,  to  the  suction  pipe,  for  the  purpose  of  priming  the 
pump. 

Q.   When  the  pump  is  in  position  for  piping,  what  care  should 
be  taken?     A.  That  the  pipes  are  of  proper  length,  so  as  not  to 
bring  any  undue  strain  upon  them  in  connecting  them  to  the  pump 
as  in  that  case  they  will  be  liable  to  give  trouble  by  breaking  or 
working  the  joints  loose  and  leaking. 

Q.  Does  any  pipe  have  an  effective  diameter  as  great  as  its 
nominal  diameter?  A.  No;  because  the  sides  retard  the  flow  of 
the  liquid  ;  there  is  a  neutral  film  of  liquid  which  practically  does 
not  move. 

Q.  Upon  what  does  the  thickness  of  this  film  of  liquid  depend? 
A.  Upon  the  viscosity  (commonly  miscalled  the  "  thickness  ") 
of  the  liquid  ;  upon  the  roughness,  material  and  diameter  of  the 
pipe  ;  the  pressure,  etc. 

Q.  When  long  lines  of  pipe  are  used,  should  the  diameter  of  the 
pipe  be  the  same  all  the  way  along,  or  should  there  by  sections 
be  decreasing  diameter,  as  the  distance  from  the  pump  increases  ? 
A.  Most  emphatically,  the  pipe  diameter  should  remain  constant 
clear  out  to  the  end. 


HANDBOOK  .ON    ENGINEERING.  575 

TAKING  CARE  OF  A  PUMP. 

Q.  What  can  be  said  about  taking  care  of  a  pump?  A.  In 
places  where  an  inferior  grade  of  labor  is  employed,  oil  and  dirt 
are  sometimes  found  covering  the  steam  chest  and  pump  to  the 
depth  of  an  inch  in  thickness ;  stuffing  boxes  are  allowed  to  go 
leaky  and  get  loose  ;  the  valve  motion  is  never  looked  after ;  lost 
motion  is  never  taken  up,  and  the  pump  will  be  let  run  in  a  slip- 
shod way  for  months,  until  some  accident  occurs.  This  will 
sometimes  exist  in  places  where  the  engine  is  well  taken  care  of. 

Q.  Should  not  as  good  care  be  taken  of  a  steam  pump  as  of 
an  engine?  A.  Yes.  It  is  a  steam  engine,  and  the  fact  that  it 
has  generally  but  little  adjustability,  should  not  render  it  liable  to 
lack  of  care. 

Q.  What  is  a  very  common  thing  for  pump  runners  to  do  when 
anything  happens  ?  A.  To  condemn  the  pump  at  once  without 
finding  out  the  cause  of  the  trouble. 

Q.  What  is  one  reason  of  this?  A.  The  man  who  understands 
an  ordinary  engine,  will  often  become  quite  perplexed  when  he 
examines  the  steam  end  of  a  direct  acting  steam  pump,  because 
he  does  not  comprehend  the  principal  feature  of  its  construc- 
tion—  that  all  direct  acting  steam  pumps  which  have  no  fly 
wheels  and  cranks,  must  generally  have  an  auxiliary  piston  in 
order  to  carry  them  over  the  "  dead  center."  A  direct  acting 
steam  pump  is  really  a  double  engine ;  a  plain,  flat  slide  valve 
admitting  steam  to  a  small  piston,  which  in  turn  operates  the 
main  valve,  which  gives  steam  by  the  usual  arrangement  to  the 
main  piston. 

Q.  What  would  save  firemen  and  engineers  much  trouble  with 
steam  pumps?  A.  If  they  would  take  the  trouble  to  examine 
their  pumps  carefully,  and  find  out  the  way  their  valves  were 
arranged  and  actuated. 

Q.  Upon    what  does  the    successful  performance    of   a  pump 


576  HANDBOOK    ON    ENGINEERING. 

depend,  in  great  measure?  A.  Upon  its  proper  selection  from 
among  the  many  patterns  differing  from  each  other  in  size,  pro- 
portion and  general  arrangement. 

Q.  What  may  be  said  about  the  selection  of  pumps?  A. 
Pumps  are  often  selected  improperly  for  their  work.  As  an  illus- 
tration, a  man  who  wishes  to  use  a  circulating  pump  for  a  surface 
condenser,  where  the  water  pressure  upon  the  pump  cylinder  will 
never  exceed  5  to  10  pounds,  will  buy  a  pump  intended  for  boiler 
feed  work,  and  having  its  steam  cylinder  about  three  times  the 
area  of  its  pump  cylinder. 

Q.  What  will  be  the  result  in  such  a  case?  A.  There  will  be 
little  or  no  pressure  in  the  steam  cylinder  when  working  on  the 
condenser ;  and  while  there  is  pressure  sufficient  to  move  the 
main  piston,  there  is  not  enough  to  operate  the  auxiliary  piston 
with  positiveness. 

Q.  In  ordering  a  pump,  or  in  asking  estimates,  what  informa- 
tion should  be  given?  A.  In  ordering  a  pump,  it  is  to  the  inter- 
est of  the  purchaser  to  fully  inform  the  maker  or  seller  on  the 
following  questions :  1st.  For  what  purpose  is  the  pump  to  be 
used?  What  is  the  average  steam  pressure?  2d.  What  is  the 
liquid  to  be  pumped  ;  and  is  it  hot  or  cold,  clear  or  gritty,  fresh, 
salt,  alkaline  or  acidulous?  3d.  What  is  the  maximum  quantity 
to  be  pumped  per  minute  or  hour?  4th.  To  what  height  is  the 
liquid  to  be  lifted  by  suction,  and  what  is  the  length  of  the  suction 
pipe,  and  the  number  of  elbows  or  bends?  5th.  To  what  height 
is  the  liquid  to  be  pumped,  and  what  is  the  length  of  discharge 
pipe? 

Q.  How  can  an  engineer  familiarize  himself  with  the  direction 
of  the  auxiliary  steam  and  exhaust  passages:  A.  By  means  of 
a  piece  of  wire. 

Q.  What  is  the  special  thing  to  look  after  in  duplex  pumps? 
A.  That  all  packings  are  adjusted  uniformly  on  both  sides. 

Q.  What  would  be  the  result  of  having  the  packings  different 


HANDBOOK   ON    ENGINEERING.  577 

upon  the  two  sides  of  a  duplex  pump?  A.  The  machinery  would 
run  unsteadily. 

Q.  If  a  pump  works  badly,  what  should  be  about  the  first  thing 
to  look  at?  A.  The  connections. 

Q.  When  a  pump  is  first  connected,  what  should  be  done? 
A.  It  should  be  blown  through  to  remove  dirt ;  if  it  be  of  the 
class  which  will  permit  of  removing  the  bonnets  and  blowing 
through,  that  should  be  done. 

Q.  What  pump  piston  speed  is  recommended  for  continuous 
boiler  feeding  service?  A.  About  50  feet  per  minute. 

Q.  What  may  be  said  about  the  care  and  use  of  steam  pumps 
of  all  kinds?  A.  It  is  important  that  the  pump  be  properly  and 
thoroughly  lubricated ;  that  all  stuffing-box,  piston  and  plunger 
packings  be  nicely  adjusted  ;  not  so  tight  as  to  cause  undue  fric- 
tion ;  nor  so  slack  as  to  leak  badly. 

Q.  In  which  end  of  a  steam  pumping  machine  is  there  most 
likely  to  be  trouble?  A.  In  the  water  end. 

Q.  If  a  pump  slams  and  hammers  in  its  water  end,  is  it  neces- 
sarily defective  in  its  water  cylinder?  A.  No;  it  may  be  that 
there  is  no  suction  chamber,  or  not  enough  ;  or  sometimes  it  slams 
because  the  suction  pipe  is  not  large  enough. 

Q.  What  are  very  common  defects  in  cheap  grades  of  pumps? 
A.  Too  little  valve  area  in  the  pump  end ;  too  great  lift  for  the 
valves. 

Q.  What  are  the  principal  causes  of  pumps  refusing  to  lift 
water  from  the  source  of  supply?  A.  Among  these  may  be 
mentioned  leaky  suction  pipes,  worn  out  pistons,  plungers,  pack- 
ings or  water  valves ;  rotten  gaskets  on  joints  in  piping  or  pump ; 
and  sometimes  a  failure  to  properly  prime  the  pump  as  well  as 
the  suction  pipe. 

Q.  What  is  one  great  cause  of  a  pump  refusing  to  lift  water 
when  first  started?  A.  It  often  happens  that  a  pump  refuses  to 
lift  water  while  the  full  pressure  against  which  it  is  expected  to 

37 


578  HANDBOOK    ON    ENGINEERING. 

work  is  resting  upon  the  discharge  valves,  for  the  reason  that  the 
air  within  the  pump  chamber  is  not  dislodged,  but  only  compressed, 
by  the  motion  of  the  plunger.  It  is  well,  therefore,  to  arrange 
for  running  without  pressure  until  the  air  is  expelled  and  water 
follows ;  this  is  done  by  placing  a  valve*  in  the  delivery  pipe 
and  providing  a  waste  delivery,  to  be  closed  after  the  pump  has 
caught  water. 

Q.  Sometimes  when  starting,  the  water  may  not  come  for  a 
long  time  ;  what  is  the  best  thing  to  do  in  this  case?  A.  First, 
open  the  little  air  cock,  which  is  generally  located  in  the  top  of 
the  pump,  between  the  discharge  valves  and  the  air  chamber,  to 
let  off  any  accumulation  of  air,  which  may  there  be  confined 
under  pressure.  Very  often,  by  relieving  the  pump  of  this  air 
pressure,  it  will  pick  up  its  water  by  suction  and  operate 
promptly. 

Q.  What  precaution  must  be  taken  in  priming  the  pump?  A. 
The  air  cock,  which  should  be  provided  at  the  top  of  the  pump, 
should  be  opened  to  allow  the  escape  of  the  air  from  the  suction 
pipe  and  from  the  pump,  and  then  the  valve  in  the  priming  pipe 
should  be  opened.  The  pump  should  then  be  started  slowly,  as 
it  aids  in  more  completely  filling  the  pump  cylinders,  which 
otherwise,  might  not  occur  and  the  pump  might  fail  to  lift  water. 

Q.  Is  there  any  advantage  in  having  air  in  the  suction?  A. 
Sometimes  a  small  amount  of  air  let  into  the  suction  will  cause  less 
jarring  when  the  duty  is  very  heavy. 

Q.  What  may  be  said  about  pumping  hot  water?  A.  Where 
the  hot  water  is  very  hot,  it  should  gravitate  to  the  pump,  instead 
of  an  attempt  being  made  to  draft  it. 

Q.  In  the  plunger  pumps,  'what  is  about  the  only  wearing  part 
of  the  water  end?  A.  The  packing  of  the  plunger  stuffing-boxes. 

Q.  How  can  a  pump  be  prevented  from  freezing?  A.  By 
having  draining  cocks  and  opening  them  when  the  pump  is 
idle. 


HANDBOOK    ON    ENGINEERING.  579 

Q.  What  may  be  said  about  leather  piston  packing  for  water 
cylinders?  A.  For  cold  water,  or  sandy,  gritty  water,  the 
leather  packing  has  many  points  to  commend  it ;  it  makes  a 
tight  piston,  and  one  that  is  the  least  destructive  to  pump 
cylinders. 

Q.  What  is  the  best  way  to  handle  the  square  packing  mostly 
employed,  which  is  composed  of  alternate  layers  of  cotton  and 
rubber?  A.  Cut  the  lengths  a  trifle  short,  then  there  will  be 
room  for  the  packing  to  swell  and  not  cause  too  much  friction.  We 
have  known  pistons  where  this  precaution  has  not  been  taken  to 
be  fastened  so  securely  in  the  cylinder  by  the  swelling  of  the  dry 
packing,  that  full  steam  pressure  could  not  move  tliem. 

Q.  What  is  the  remedy  in  such  a  case?  A.  Remove  the 
follower,  take  out  the  different  layers  of  packing  and  shorten  their 
lengths. 

Q.  What  is  the  reason  that  some  soft  waters  corrode  pipes  so 
often?  A.  Because  they  contain  a  large  proportion  of  oxygen. 

Q.  Will  a  pump  with  a  6"  water  cylinder  and  a  6"  steam  cylin- 
der force  water  into  a  boiler,  the  discharge  from  water  cylinder 
being  4"  diameter;  boiler  pressure,  80  Ibs.?  A.  A  pump  with  a 
6"  water  cylinder  and  6"  steam  cylinder  will  not  force  water  into 
the  boiler  which  supplies  it,  no  matter  what  the  steam  pressure, 
nor  what  the  size  of  discharge  pipe.  It  will  not  move.  The 
pressures  would  be  equalized  and  there  would  be  nothing  to  over- 
come friction  of  steam  and  water  in  pipes,  and  cylinder.  The 
foregoing  case  supposes  that  the  water  is  to  be  lifted  to  the  pump  ; 
or  at  least  that  there  shall  be  no  head ;  also,  that  there  shall  be 
no  fall  from  pump  to  boiler.  If  there  were  sufficient  head  or  fall 
to  overcome  all  the  various  frictions,  and  no  lift,  the  pump 
would  apparently  work ;  but  really,  the  water  piston  would  be 
dragging  the  steam  piston  along. 

Q.  How  may  acids  be  pumped?  A.  By  what  is  known  as 
blowing  up ;  that  is,  by  employing  a  pump  to  put  pressure  upon 


580  HANDBOOK    ON    ENGINEERING. 

the  acid  in  a  closed  vessel,  thereby  forcing  it  through  a  pipe 
placed  in  the  bottom  of  the  vessel. 

Q.  In  case  any  wearing  part  of  a  pump  gets  to  cutting,  what 
should  be  done?  A.  If  it  is  not  practicable  to  stop  the  pump  nor 
to  reduce  its  speed,  the  part  which  is  getting  damaged  should  be 
given  very  liberal  oiling. 

Q.  What  is  the  best  oil  for  this  purpose?  A.  That  depends  on 
the  nature  of  the  cutting  surfaces,  and  on  the  pressure  therein  ; 
the  mineral  oils  are  generally  more  cooling  than  others,  although 
they  have  less  body  to  resist  squeezing. 

% 
CALCULATING  THE  BOILER  FOR  A  STEAM  PUMP. 

The  amount  of  work  which  a  bgiler  has  to  do  is  very  easy  of 
determination.  Given  the  largest  number  of  gallons  which  a 
pump  will  be  required  to  pump  per  minute,  and  the  height  in  feet 
from  the  surface  of  the  well  from  which  the  water  is  drawn,  to 
the  point'of  discharge,  you  can  easily  tell  by  multiplying  by  8| — 
the  weight  in  pounds  of  one  gallon  —  the  number  of  foot  pounds 
of  power  consumed  per  minute  in  lifting  the  water,  adding  a  cer- 
tain percentage  for  friction  of  the  machine  and  of  water  in  the 
pipe,  we  have  the  total  number  of  foot  pounds  consumed  per 
minute,  and  this  divided  by  33,000  will  be  the  horse  power 
consumed. 

The  allowance  for  friction  will  vary  with  the  style,  size  and 
condition  of  the  pump,  the  size  of  the  pipe,  and,  above  all,  the 
manner  in  which  the  pipe  is  connected  up,  the  number  of  right 
angle  turns,  etc. 

This  may  be  arrived  at  in  another  way.  A  column  of  water 
2.3  feet  in  height  exerts  a  pressure  of  one  pound.  Allowing  the 
.3  for  friction,  we  can,  by  dividing  the  total  left  in  feet  by  two, 
get  at  the  pressure  per  square  inch,  which  is  being  exerted  against 
the  water  piston  or  plunger,  and  multiplying  by  the  number  of 


HANDBOOK    ON    ENGINEERING.  581 

square  inches  in  that  piston  gives  the  total  pressure  against  which 
the  pump  is  working.  This  multiplied  by  the  piston  speed  in  feet 
minutes,  and  divided  by  33,000,  will  give  the  lift  in  horse  power. 
In  this  case,  as  in  the  other,  the  lift  must  be  calculated  from  the 
surface  of  the  supply,  and  not  from  the  pump,  when  the  pump  is 
lifting  its  supply.  If  the  water  flows  to  the  pump  it  must  be 
calculated  from  the  height  of  the  water  cylinder.  An  allowance 
of,  say,  25  per  cent, -should  be  made  above  the  horse  power  thus 
shown,  in  order  to  provide  for  contingencies,  and  to  be  on  the 
safe  side. 

In  selecting  a  boiler  to  do  this  work,  it  must  be  borne  in  mind 
that  a  boiler  which  is  sold  for  a  certain  horse  power,  is  supposed 
to  be  able  to  furnish  that  power  in  connection  with  a  good  steam 
engine ,  and  they  are  not  apt  to  be  overrated .  Now ,  the  steam  pump 
as  usually  built,  does  not  approach  in  economy  the  ordinary  steam 
engine,  and,  therefore,  a  boiler  which  will  develop,  twenty-five 
horse  power  in  connection  with  a  good  engine  would  be  too  small 
for  a  pump  which  was  required  to  do  the  same  amount  of  work. 
The  evaporation  of  30  pounds  of  water  per  hour  from  feed  at  100 
degrees  Fahr.  into  steam  of  70  Ibs.  pressure,  has  been  adopted  by 
several  authorities  as  a  horse  power.  Any  good  automatic  cut-off 
will  run  on  this  amount  of  water,  and  if  an  estimate  can  be  made 
of  the  comparative  performance  of  the  pump  under  consideration, 
a  close  approximation  to  the  desired  size  of  boiler  can  be  made. 

THE  WORTHINGTON  WATER  METER. 

The  counter  registers  cubic  feet ;  one  foot  being  7T%8^  gallons, 
United  States  standard.  It  is  read  in  the  same  way  as  registers 
of  gas  meters.  The  following  example  and  directions  may  be  of 
use  to  those  unacquainted  with  the  method:  If  a  pointer  is 
between  two  figures,  the  smaller  one  must  invariably  be  taken. 
Suppose  the  pointers  of  the  dials  to  stand  as  in  the  engraving. 


582 


HANDBOOK   ON    ENGINEERING. 


The  reading  is  6,874  cubic  feet.  From  the  dial  marked  ten  wa 
get  the  figure  4 ;  from  the  next,  marked  hundred,  the  figure  7 ; 
from  the  next,  marked  thousand,  the  figure  8 ;  from  the  next, 


Fig.  293.  Worthington  water  meter, 
marked  ten  thousand,  the  figure  6.  The  next  pointer  being 
between  ten  and  1,  indicates  nothing.  By  subtracting  the  read* 
ing  taken  at  one  time,  from  that  taken  at  the  next,  the  consump- 
tion of  water  for  the  intermediate  time  is  obtained. 

TABLE   OF   PRESSURE   DUE   TO    HEIGHT. 


s 


H 


li 

ft  . 

a* 

W>    W 

-3  x 


5j 

Si 


P    . 

«>  ,d 


s . 
II 

ft  . 


0.43 
2.16 
4.33 


6.49 
8.66 
10.82 


12.99 
15.16 
17.32 


19.49 
21.65 
23.82 


25.99 
28  15 
30.32 


32.48 
34  65 
36.82 


38.98 
41.15 
43  31 


HANDBOOK    ON    ENGINEERING. 


583 


TABLE  OF  DECIMAL   EQUIVALENTS  OF  Sths,  16ths, 
32ds  AND  64ths  OF  AN  INCH. 


Sths. 

32ds. 

64ths. 

64ths. 

i  =  .125 

SV  =  .03125 

/4-  =  .015625 

f|  =  .546875 

I  =  .25 

-3%  =  .09375 

^  =  .046875 

i  =  .578125 

|  =  .375 

-359-  ==  .15625 

•ft  =  .078125 

-J  =  .609375 

i  =  .50 

3£  _  .21875 

•h  =  .109375 

jfi  =  .640625 

|  =  .625 

^  =  .28125 

•fy  =  .140625 

||  =  .671875 

I  =  .75 

Ji  =  .34375 

iri  =  .171875 

||  =  .703125 

1  =  .875 

$  =  .40025 

ir|  =  .203125 

jj  =  .734375 

Jf  =  .46875 

ir|  =  .234375 

||  =  .765625 

LJ  =  .53125 

irj  =  .265625 

i  =  .796875 

leths. 

if  =  059375 

irf  •==  .296875 

f  =  .828125 

|^  =  .65625 

Ji  =  .328125 

|  =  .859375 

A-  =  .0625 

f|  =  .71875 

I  =  .359375 

f}  =  .890625 

A  =  1875 

|4  =  .78125 

Jf  =  .390625 

^  =  .921875 

-,V  =  .3125 

f|  =  .84375 

|f  ==  .421875 

i  =  .953125 

f6-  =  .4375 

|f  =  .90625 

§}  ==  .453125 

||  =  .984375 

A  =  .5025 

|i  =  .96875 

J  =  .484375 

H  =  .6875 

|3  _-  .515625 

||  =  .8125 

[f  =  .9375 

LATENT   HEAT   OF   LIQUIDS,    UNDER   A   PRESSURE 
OF  30  INCHES  OF  MERCURY. 

(TREATISE  ON  HEAT,  BY  THOMAS  BOX.) 


Latent  Heat 
in  Units. 

Increase  of  Tempe- 
rature of  Liquid, 
if  Heat  had  not 
become  Latent. 

Water  

966 

966° 

Hegnault. 

Alcohol  

457 

735° 

Ure. 

Ether  

313 

473° 

a 

Oil  of  Turpentine  

184 

390° 

tt 

184 

443° 

1C 

The  boiling  point  of  different  liquids  varies;  and  the  boiling  point 
of  a  liquid  varies  with  the  pressure 


584 


HANDBOOK    ON    ENGINEERING. 


O  00  00  b- 

r-^  CO 


O 

00  iQ  Oi 
00 


•  .    02 

*  00    P 

S  ajD 

2§* 


•w^   O  -~ 

5   jj| 

a   5   S   rv 


HANDBOOK    ON    ENGINEERING.  585 

CAPACITY  OF  SQUARE   CISTERNS  IN  U.  S.  GALS. 


5X5 

5X6 

5X7 

5X8 

5X9 

5X10 

6X6 

6X7 

6X8 

6X9 

6X10 

5  ft.. 

935 

1122 

1309 

1496 

1683 

1870 

1346 

1571 

1795  2020 

2244 

54  ft.. 

1028 

1234 

1440 

1645 

1851 

2057 

1481 

1728 

1975 

2221 

2469 

6  ft.. 

1122 

1346 

1571 

1795 

2019 

2244 

1615 

1885 

2154 

2423 

2693 

64ft.- 

1215 

1459 

1702 

1945 

2188 

2431 

1750 

2042 

2334 

2625 

2917 

7  ft.. 

1309 

1571 

1833 

2094 

2356 

2618 

1884 

2199 

2513 

2827 

3142 

74ft.. 

1403 

1683 

1963 

2244 

2524 

2800 

2019 

2356 

2693 

3029 

3366 

8  ft.. 

1496 

1795 

2094 

2393 

2693 

2992 

2154 

2513 

2872 

3231 

3592 

84ft.. 

1589 

1907 

2225 

2543 

2861 

3179 

2288 

2670 

3052 

3433 

3816 

9  ft.. 

1683 

2020 

2356 

2693 

3029 

3366 

2423 

2827 

3231 

3635 

4041 

94ft.. 

1776 

2132 

2487 

2842 

3197 

3553 

2558 

2984 

3412 

3837 

4265 

10  ft.. 

1870 

2244 

2618 

2992 

3366 

3470 

2692 

3142 

3591 

4039 

4489 

6X11 

6X12 

7X7 

,7X8 

7X9 

7X10 

7XH 

7X12 

8X8 

8X9 

5  ft.. 

2468 

2693 

1832  2094 

2356 

2618 

2880 

3142 

2394 

2693 

54  ft.  . 

2715 

2962 

2016 

2304 

2592 

2880 

3168 

3456 

2633 

2962 

6  ft.. 

2962 

3231 

2199 

2513 

2827 

3142 

3456 

3770 

2872 

3231 

64ft.. 

3209 

3500 

2382 

2722 

3063 

3403 

3744 

4084 

3112 

3500 

7  ft.. 

3455 

3770 

2565 

2932 

3298 

3665 

4032 

4398 

3351 

3770 

74ft.. 

3702 

4039 

2748 

3141 

3534 

3927 

4320 

4712 

3590 

4039 

8  ft.. 

3949 

4308 

2932 

3351 

3770 

4189 

4608 

5026 

3830 

4308 

84ft.. 

4196 

4577 

3115 

3560 

4005 

4451 

4896 

5340 

4069 

4578 

9  ft.. 

4443 

4847 

3298 

3769 

4341 

4712 

5184 

5655 

4308 

4847 

94ft.. 

4689 

5116 

3481 

3979 

4576 

4974 

5472 

5969 

4548 

5116 

10  ft.. 

4936 

5386 

3664 

4188 

4712 

5236 

5760 

6283 

4788 

5386 

WEIGHT    OF    WATER. 

1  cubic  inch 03617  pound. 

12  cubic  inches 434      pound. 

1  cubic  foot  (salt) 64.3          pounds. 

1  cubic  foot  (fresh) 62.425      pounds. 

1  cubic  foot 7.48        U.  S.  Gallons. 

NOTE.  —  The  center  of  pressure  of  a  body  of  water  is  at  two-thirds 
the  depth  from  the  surface. 

To  find  the  pressure  in  pounds  per  square  inch  of  a  column  of  water, 
multiply  the  height  of  the  column  in  feet  by  .434.  Every  foot  elevation 
is  called  (approximately)  equal  to  one-half  pound  pressure  per  square 
inch. 


586 


HANDBOOK    ON    ENGINEERING. 


SHOWING    U.   S.    GALLONS   IN    GIVEN 
CUBIC   FEET. 


NUMBER  OF 


Cubic 
Feet. 

Gallons. 

Cubic 
Feet. 

Gallons. 

Cubic  Feet. 

Gallons. 

0.1 

0.75 

50 

374.0 

9,000 

67,324.6 

0.2 

1.50 

60 

448.8 

10,000 

74,805.2 

0.3 

2.24 

70 

523.6 

20,000 

149,610.4 

0.4 

2.99 

80 

598.4 

30,000 

224,415.6 

0.5 

3.74 

90 

673.2 

40,000 

299,220.7 

0.6 

4.49 

100 

748.0 

50,000 

374,025.9 

0.7 

5.24 

200 

1,496.1 

60,000 

448,831.1 

0.8 

5.98 

300 

2,244.1 

70,000 

523,636.3 

0.9 

6.73 

400 

2,992.2 

80,000 

598,441,5 

1 

7.48 

500 

3,740.2 

90,000 

673,246.7 

2 

14.9 

600 

4,488.3 

100,000 

748,051.9 

3 

22.4 

700 

5,236.3 

200,000 

1,496,103.8 

4 

29.9 

800 

5,984.4 

300,000 

2,244,155.7 

5 

37.4 

900 

6,732.4 

400,000 

2,992,207.6 

6 

44.9 

1,000 

7,480.0 

500,000 

3,740,259.5 

7: 

52.4 

2,000 

14,961.0 

600,000 

4,488,311.4 

8 

59.8 

3,000 

22,441.5 

700,000 

5,236,363.3 

9 

67.3 

4,000 

29,922.0 

800,000 

5,984,415.2 

10 

74.8 

5,000 

37,402.6 

900,000 

6,732,467.1 

20 

149.6 

6,000 

44,883.1 

1,000,000 

7,480,519.0 

30 

224.4 

7,000 

52,363.6 

40 

299.2 

8,000 

59,844.1 

From  the  above  any  cubic  feet  reading  can  readily  be  converted  into 
U.  S.  gallons,  as  follows: 

How  many  gallons  are  represented  by  53,928  cubic  feet? 
50,000  cubic  feet  =  374,025.9  gallons. 
3,000       «         "     =    22,441.5         " 
900       "         "     =      6,732.4         " 
20       <f         "     =.        149.6        " 
8       "         "     =  59.8         " 


53,928  cubic  feet  =*  403,409.2  gallons 


HANDBOOK   ON   ENGINEERING. 


587 


SHOWING  COST  OF  WATER  AT  STATED  RATES 
PER  1000  GALLONS. 


Number 
of 
Cubic 
Feet. 

COST  PER  1000  GALLONS. 

5 
Cents. 

6 
Cents. 

8 
Cents. 

10 
Cents. 

15 
Cents. 

20 
Cents. 

25 
Cents. 

30 
Cents. 

20 

$0  007 

$0.009 

$0.012 

$0-015 

$0.021 

$0.030 

$0.037 

$0.045 

40 

0.015 

0.018 

0.024 

0.030 

0.045 

0  060           0.075 

0.090 

60 

0.022 

0.027 

0.036 

0.045 

0.066 

0.090 

0.112 

0.135 

80 

0.030 

0.036 

0.048 

0.060 

0.090 

0  120 

0.150 

0.180 

100 

0.037 

0.049 

0.060 

0.075 

0.111 

0.150 

0.187 

0.224 

200 

0.075 

0.090 

O.f20 

0.150 

0.225 

0.299 

0.374 

0.449 

300 

0.112 

0.135 

0.180 

0.224 

0.336 

0.449 

0.561 

0.673 

400 

0.150 

0.180 

0.239 

0.299 

0.450 

0.598 

0-748 

0.898 

500 

0.188 

0.224 

0.299 

0.374 

0.564 

0.748 

0.935 

1.122 

600 

0.224 

0.269 

0.359 

0.449 

0.448 

0.898 

1.122 

1.346 

700 

0.262 

0.314 

0.419 

0.524 

0-786 

1.047 

1.309           1-571 

800 

0.299 

0.350 

0.479 

0.598 

0-897 

1.197 

1.496           1-795 

900 

0.337 

0.404 

0.539 

0.673 

1.011 

1  346 

1.683          2.020 

1,000 

0-374 

0.449 

0.598 

0.748 

1.122 

1  496 

1.870 

2.244 

2,000 

0.748 

0.898 

1.197 

1.498 

2.244 

2.992 

3.740 

4-488 

3,000 

1.122 

1.346 

1-795 

2-244 

3.366 

4.488 

5.610 

6*732 

4,000 

1.496 

1.795 

2-393 

2.992 

4.488 

5.984 

7.480 

8.976 

5,000 

1.870 

2.244 

2-992 

3-740 

5.610 

7.480 

9.350 

11.220 

6,000 

2.244 

2.692 

3.590 

4.488 

6.732 

8.976 

11.220 

13.464 

7,000 

2.618 

3-141 

4.189 

5.236 

7.854 

10.472 

13.090 

15.708 

8,000 

2.992 

3.590 

4-787 

5-984 

8.976 

11.968 

14.961 

17.953 

9,000 

3.366 

4.039 

5.385 

6.732 

10.098 

13.464 

16-831 

20.197 

10,000 

3.74 

4.488 

5-984 

7-480 

11.122 

14.961 

•  18.701 

22.441 

20,000 

7.48 

8.976 

11.96& 

14.961 

22.443 

29.992 

37-402 

44.882 

30,000 

11.22 

13.46 

17.95 

22-44 

33.664 

44.88 

56.10 

67.32 

40,000 

14.96 

17.95 

23-94 

29.92 

44.885 

59.84 

74-10 

89.77 

50,000 

18.70 

22.44 

29.92 

37.40 

56.103 

74.80 

93-50 

112.20 

60,000 

22.44 

26.92 

35.90 

44.88 

67.323 

89.76 

112.20 

134.64 

70,000 

26.18 

31-41 

41.89 

52.36 

78.543 

104.72 

130.90 

157-08 

80,000 

29.92 

35.90 

47-87 

59.84 

89.766 

119.68 

149.61 

179.53 

90,000 

33-.  66 

40.39 

53.85 

67.32 

100.  98b 

134  64 

168-31 

201.97 

100,000 

37.40 

44.88 

59.84 

74.80 

111.22 

149.61 

187-01 

224.41 

200,000 

74.81 

89.76 

119.68 

149.61 

224.43 

299  22 

374.02 

448-82 

300,^00 

112.20 

134.64 

179.53 

224.41 

336.64 

448.83 

561.03 

673.24 

400,000 

149-61 

179.53 

239.37 

299.22 

448-85 

598  44 

748.05 

897-66 

500,000 

187.01 

224.41 

299.22 

374.02 

561.03 

748.05 

935.06 

1122.07 

600,000 

224.41 

269.29 

359.06 

448  83 

673-23 

897.66 

1122.07 

1346.49 

700,000 

261.81 

314.18 

418.90 

523.63 

785-43 

1047.27 

1309.08 

1570.88 

800,000 

299  22 

359.06 

478.75 

598.44 

897-66 

1196  88 

1496.10 

1795.32 

900,000 

336.62 

403.94 

538.59 

673.24 

1009-  86 

1346.49 

1683.11 

2019.73 

1,000,000 

374.02 

448.83 

598.44 

748.05 

1122,06 

1498.10 

1870.12 

2244.15 

HANDBOOK    ON    ENGINEERING. 


OOOOOO 


i-t 


OOOOOO 


CO  tO  CO  Oi 

oood 


o    •o'ooo'ooo'o'oor-i 


•OOOOOOOOOOOt-i 


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HANDBOOK    ON    ENGINEERING. 


589 


SHOWING  HOW  WATER  MAY  BE  WASTED. 

GALLONS   DISCHARGED    PER   HOUR  THROUGH   VARIOUS    SIZED  ORIFICES 
UNDER    STATED    PRESSURES. 


= 

-M 

Diameters  of  Orifices  in  Inches  and  Fractions  of  an  Inch. 

"S  S 

3  S  <D 

HH 

£|  | 

i 

1 

i 

1 

1 

1 

l£ 

11 

H 

2 

m 

inch 

inch 

inch 

inch 

inch 

inch 

inch 

inch 

inch 

inch 

Cu  GO 

20 

8.66 

300 

720 

1260 

1920 

2760 

4920 

7380 

11100 

15120 

19740 

40 

17.32 

450 

960 

1800 

2760 

3960 

6720 

10920 

15720 

21360 

27960 

60 

25.99 

540 

1200 

2160 

3480 

4800 

8580 

13380 

19200 

26220 

34260 

80 

34.65 

620 

1380 

2460 

3840 

5580 

9840 

15480 

22260 

30300 

39540 

100 

43.31 

690 

1560 

2760 

4320 

6240 

11040 

17280 

24900 

33900 

44280 

120 

51.98 

780 

1780 

3000 

4740 

6840 

12120 

18960 

27240 

37440 

48480 

140 

60.64 

816 

1860 

3300 

5100 

7320 

13020 

20160 

29460 

39080 

52320 

150 

64.97 

840 

1920 

3420 

5280 

7620 

13560 

21180 

30480 

41460 

54120 

175 

75.80 

900 

2040 

3660 

5700 

8220 

14640 

22800 

32880 

44940 

58560 

2CO 

86.63 

960 

2220 

3900 

6120 

8760 

15600 

25020 

35880 

47880 

62580 

235 

101.79 

1080 

2460 

4320 

8280 

11160 

17100 

26760 

38520 

52260 

68460 

The  pressure  or  head  of  water  is  taken  at  the  orifice,  no  allowance 
being  made  for  friction  in  the  pipe.  In  practical  calculations  to  deter- 
mine the  height  which  water  can  be  thrown,  the  head  consumed  by  the 
friction  of  the  water  in  flowing  from  the  source  to  the  orifice  must  be 
considered. 


IGNITION  POINTS   OF  VARIOUS  SUBSTANCES. 

Phosphorus    ignites    at     .     ,  ....  150°  Fahr. 

Sulphur  "        "     .     .     .     . 500°      « 

Wood  "        "     .     .     .     .     .     .     .     .     =     c     .     .     .  800°      " 

Coal  .         "        "      .     .     .     ..........  1000°      " 

Lignite,  in  the  form  of  dust,  ignites  at    .     .     ,     .     .     c     .     .  150°      " 

CaimelCoal,         "  ""        "     .     .     ......  200°      " 

Coking  Coal,        "  "        "     .     .     .     .     .     .     .     .  250°      " 

Anthracite,  "  «  "       " 300°      " 


590  HANDBOOK   ON    ENGINEERING. 


CHAPTER    XX, 
THE  INJECTOR  AND  INSPIRATOR. 

The  energy  of  motion  of  a  body  is  well  known  to  be  the  prod- 
act  of  its  mass  by  the  half  square  of  its  velocity ;  hence,  it  is 
possible  to  communicate  to  a  body  of  little  weight  a  large  amount 
of  energy  by  moving  it  fast  enough,  and  in  fact,  the  energy  of 
motion  would  only  be  limited  by  the  speed  which  can  be  given 
the  body.  In  this  way  a  small  weight  of  steam  flowing  from  an 
orifice  into  a  properly  shaped  jet  of  water  is  condensed,  while  the 
velocity  of  the  steam  is  greater  than  if  flowing  into  air ;  the 
energy  thus  communicated  is  made  sufficiently  great  by  increasing 
the  weight  of  steam,  which  can  be  done  by  increasing  the  area  of 
the  steam  way,  until  we  find  such  jet  pumps  adapted  to  many 
purposes.  There  are,  however,  two  which  are  of  interest  to  us 
in  this  connection,  the  well-known  injector  and  inspirator,  with 
the  large  number  of  lifting  and  non-lifting  varieties,  all  differing 
in  details  as  to  form  of  nozzles,  area  of  passages,  distances 
between  nozzles,  and  that  class  of  instruments  in  which,  after  a 
certain  energy  and  velocity  have  been  reached,  the  operation  is 
rep'eated.  These  might  be  called  "  consecutive  "  instruments. 
The  illustrations  in  this  book  show  some  of  the  simplest  and 
adjustable  kinds.  Within  a  few  years  the  principle  of  increase  of 
energy  by  increase  of  mass  or  velocity  has  been  applied  by  in- 
creasing the  mass  of  steam  used  until  we  find  that  not  only  can  a 
few  pounds  weight  of  steam  put  into  a  boiler,  a  good  many  more 
pounds  of  water  at  a  much  higher  temperature  than  it  had,  but 
that  in  a  non-condensing  engine  it  is  possible,  by  using  the  ex- 
haust in  part,  to  put  into  the  boiler  at  a  much  higher  pressure 


HANDBOOK   ON    ENGINEERING.  591 

and  temperature,  a  weight  of  water,  which  is  still   greater  than 
that  of  the  steam  moving  it. 

When  the  injector  first  made  its  appearance  it  was,  by  many, 
considered  as  almost  a  paradox,  especially  by  those  who  looked 
at  the  question  as  one  of  hydrostatics  only.  That  steam  from  a 
boiler  could  put  water  back  into  it  at  the  same  pressure,  and  over- 
come the  friction  of  the  passages  without  the  aid  that  a  steam 
pump  had  of  a  difference  of  piston  areas,  was  to  them  a  puzzle , 
The  use  of  exhaust  steam  at  atmospheric  pressure  for  the  purpose 
of  putting  water  into  a  boiler  at  a  pressure  of  150  Ibs.  per  square 
inch,  would  be  to  such  minds  utterly  incomprehensible.  The  use 
of  an  injector  and  inspirator,  has  this  to  recommend  them,  that 
the  feed-water  cannot  be  introduced  into  the  boiler  cold  or  nearly 
so>  but  must  be  warmed  by  contact  with  the  steam,  and  the  value 
of  this  has  been  already  shown.  In  small  boilers  where  no  heater 
is  used,  an  exhaust  injector  is  better  than  a  pump,  and  so  is  an 
ordinary  injector ;  but  the  former  includes  in  itself  an  exhaust 
heater,  saving  a  portion  of  heat  from  the  exhaust,  besides  taking 
the  power  as  heat  also ;  while,  with  the  common  injector,  the 
heat  for  power  and  raising  temperature  are  both  derived  from  the 
live  steam  in  the  boiler.  The  latter  portion  of  heat  is,  of  course, 
directly  returned  to  the  boiler  without  loss,  but  that  for  power  is 
necessarily  expended.  As  to  the  amount  of  power  used  by  pump 
and  injector  compared  with  each  other,  it  would  seem  that  the 
pump  is  most  efficient.  There  have  been  many  comparative  trials 
of  pump  and  injector,  but  the  results  have  usually  been  unsatis- 
factory from  contained  discrepancies. 

Injectors  are  of  the  automatic  type,  so  named  on  account  of  their 
ability  to  restart  when  for  any  reason  the  supply  of  either  water 
or  steam  is  momentarily  interrupted.  This  is  one  of  the  simplest 
of  its  type,  all  parts  being  accessible  by  the  simple  use  of  a  mon- 
key wrench.  Taking  off  the  bottom  plug,  the  lower  interior  jet 


592  HANDBOOK    ON    ENGINEERING. 

follows  it  out,  as  does  also  the  upper  or  steam  jet,  by  removing 
the  coupling  nut.  On  this  account  and  for  other  reasons  auto- 
matic Injectors  have  become  very  popular,  as  the  engineer  is 
enabled  to  make  his  own  repairs  where  parts  are  interchangeable 
as  in  this  Injector.  In  installing  an  Injector,  great  care  must  be 
exercised  in  getting  tight  pipe  connections,  especially  in  the 
suction  or  water  supply  pipe,  as  the  least  particle  of  air  admitted 
to  this  pipe  will  ruin  the  vacuum,  hence  the  starting  or  working 
of  the  machine.  Before  connecting  an  Injector,  from  the  fact 
that  there  is  a  chance  of  iron  scale  or  other  refuse  being  in  the 
steam  pipe,  it  should  be  blown  out  thoroughly  before  the  Injector 
is  connected,  otherwise  whatever  is  in  this  pipe  will  be  blown 
into  the  Injector  at  the  first  opening  of  the  steam  valve  and  the 
jets  entirely  clogged.  It  takes  but  the  smallest  particle  of  refuse 
of  any  kind  lodged  in  the  delivery  tube  to  destroy  the  working 
of  an  Injector.  Many  engineers  wonder  why  after  an  Injector 
has  been  in  use  for  only  a  short  time  it  will  not  work  as  when 
first  put  on.  They  do  not  seem  to  realize  that  in  most  all  water 
there  is  a  great  deal  of  solid  matter,  all  of  which  is  deposited  by 
the  action  of  the  steam  on  the  interior  and  the  jets  of  the  Injector. 
This  sediment  increases  very  rapidly,  and  very  soon  all  tapers 
and  horizontal  drill  holes  have  become  contracted  and  the  range 
of  the  Injector  destroyed.  A  solution  of  ten  parts  of  muriatic 
acid  to  one  part  of  water  will  cut  away  almost  all  the  sediment  so 
lodged  on  the  jets,  and  by  disconnecting  the  Injector  and 
immersing  the  same  in  the  above  solution  over  night  this  sedi- 
ment is  almost  sure  to  be  dissolved. 

RANGE  OF  THE  INSPIRATOR  AND  INJECTOR. 

The  Steam  pressure  at  which  an  injector  will  start  and  the 
highest  steam  pressure  at  which  it  will  work  constitute  what  is 
termed  the  "range"  of  an  injector,  and  the  inspirator  varies  with 
the  vertical  lift  and  the  temperature  of  the  feed  water. 


HANDBOOK    ON    ENGINEERING. 


593 


It  must  also  be  borne  in  mind  that  the  same  style  of  construc- 
tion in  an  injector  and  inspirator,  while  it  confines  them  to  about  a 
specific  range  between  its  lowest  starting  and  highest  working  points, 
permits  of  variation  as  to  what  the  lowest  starting  point  shall  be. 
A  style  of  construction,  which  gives  a  range  (on  say  a  2-foot  lift) 
of  25  Ibs.  to  155  Ibs.  would  permit  of  a  range  of  35  Ibs.  to  165 
Ibs.  (in  fact,  to  a  little  higher  than  165  Ibs.).  Different  manu- 
facturers, therefore,  vary  as  to  the  starting  point  in  their  stand- 
ard machines  —  aiming  to  cover  the  range  which  they  deem  most 
desirable.  Nearly  all  have  adopted  about  25  Ibs.  on  a  2-foot  lift, 
as  lowest  starting  point. 


Fig.  294.    The  World  injector. 

POSITIVE  OR  DOUBLE  TUBE  INJECTORS. 

As  before  stated,  this  class  of  injector  is  provided  with  two  sets 
f  tubes  or  jets,  one  set  adapted  to  lift  the  water  and  deliver  it  to 

88 


594  HANDBOOK   ON    ENGINEERING. 

the  second  set,  which  forces  the  water  into  the  boiler.  By  this 
arrangement,  it  is  apparent  that  inasmuch  as  the  lifting  jets 
supply  a  proportionate  amount  of  water  with  varying  steam  pres- 
sures, a  wider  range  is  obtainable  than  with  an  automatic  in- 
jector. In  the  following  cases,  it  is  better  to  use  the  double  tube 
injectors :  — 

1.  Where  the  feed  water  is  of  too  high  a  temperature  to  be 
handled  by  the  automatic  injectors. 

2.  When  a  great  range  of  steam   variation  is  accompanied  by 
the  condition  of  a  long  lift. 

The  World  injector  is  one  of  the  simplest  boiler  feeders  of  the 
double  tube  type  of  injectors.  It  is  entirely  self  contained.  It 
is  supplied  even  with  its  own  check  valve  and  operated  entirely 
by  a  single  lever,  a  quarter  of  a  turn  of  which  starts  the  lifting, 
after  which  the  completion  of  the  single  revolution  sets  the  injector 

working  to  boiler. 

• 
. 

GENERAL  SUGGESTIONS  FOR  PIPING-UP  INJECTORS  AND 
INSPIRATORS  AND  SUGGESTIONS  THAT  SHOULD  BE 
CAREFULLY  FOLLOWED  WHEN  MAKING  PIPE  CONNEC- 
TIONS. 

Steam*  —  Connect  steam  pipe  with  highest  parts  of  boiler  and 
never  connect  with  a  steam  pipe  used  for  any  other  purpose.  We 
would  recommend  a  globe  valve  being  placed  in  the  steam  pipe 

next  to  boiler  which  can  be  closed  in  case  it  is  desired  to  take  off 

. 

the  injector.  At  all  other  times  it  can  be  left  open.  When  the 
steam  connection  is  made,  be  sure  and  take  off  the  injector  before 
the  steam  is  turned  on  the  machine.  Then  blow  out  the  steam 
pipe  with  at  least  forty  pounds  steam,  which  will  remove  all  dirt 
and  scale. 

Suction*  —  This  pipe  must  be  tight,  and  if  there  is  a  valve  in  it 
the  stem  must  be  well  packed. 

To  test  the  suction  pipes  for  leaks,  plug  up  the  end  of  the  pipe 


HANDBOOK    ON   ENGINEERING. 


595 


and  then  screw  on  a  common  iron  cap  on  the  overflow ;  or  if  that 
is  not  at  hand,  unscrew  cap  X,  and  place  a  piece  of  wood  on 
top  of  valve  ;  replace  the  cap  and  the  wood  will  hold  the  valve 
from  rising ;  then  turn  on  the  steam,  which  will  locate  all  leaks. 


Fig.  295.    Complete  piping  for  injector. 


All  pipes,  whether  steam,  suction  or  delivery,  must  be  of  the 
same  or  greater  size  than  the  corresponding  branch  of  each  injec- 
tor. Have  all  piping  as  short  and  as  straight  as  possible,  and 
especially  avoid  short  turns. 


596  HANDBOOK    ON    ENGINEERING. 

If  any  old  pipe  is  used,  see  that  it  is  not  partially  filled  or 
stopped  up  with  rust. 

If  the  injector  or  inspirator  has  to  lift  the  water  very  high  ot 
draw  it  very  far,  have  the  suction  pipe  a  size  or  two  larger  than 
called  for  by  the  suction  branch  of  the  injector  or  inspirator. 

Have  the  water  supply  (suction)  pipe  independent  of  any  other 
connection.  The  suction  pipe  must  be  absolutely  air  tight ;  the 
slightest  leak,  in  most  cases,  will  prevent  the  injector  or  inspirator 
from  forcing  water  into  the  boiler. 

Always  place  a  globe  valve  in  the  suction  pipe  as  close  to  the 
injector  as  possible,  and  place  it  so  that  it  will  shut  down  against 
the  water  side  and  see  that  the  stem  is  packed  tight. 

When  using  the  injector  or  inspirator  as  NON-LIFTING,  put  two 
globe  valves  in  the  suction,  one  close  to  the  injector,  the  other  as 
far  from  it  as  you  can  conveniently,  keeping  the  one  farthest  from 
the  injector  or  inspirator  tolerably  close  throttled.  This  will 
repay  anyone  for  their  trouble.  The  check  valve  may  be  next 
to  boiler  with  a  valve  between  it  and  boiler,  the  farther  from 
injector  the  better.  If  the  injector  forces  through  a  heater,  place 
check  valve  between  injector  and  heater.  Also  place  a  valve 
between  heater  and  check  valve  so  the  latter  can  be  taken  out 
if  necessary. 

Size  of  pipes*  —  If  injector  or  inspirator  has  over  10  feet  lift, 
or  a  long  draw,  use  suction  pipe  from  strainer  to  valve  a  size 
larger  than  the  connection  on  injector,  reducing  when  it  reaches 
the  valve. 

In  all  other  cases,  use  for  all  pipes  same  size  as  injector 
connection. 

Blow-off*  —  Always  blow  out  steam  thoroughly  BEFORE  CON- 
NECTING INJECTOR,  so  as  to  remove  any  dirt,  rust  or  scale  that 
may  be  in  the  pipes. 

Caution*  —  The  suction  pipe  must  be  ABSOLUTELY  TIGHT 
throughout.  To  make  sure  that  it  is  so,  test  the  suction  as  directed. 


HANDBOOK    ON    ENGINEERING.  597 

DIRECTIONS   FOR  CONNECTING  AND  OPERATING  THE 
HANCOCK  INSPIRATOR. 

44  Stationary  "  pattern*  —  Connect  as  shown  by  cut  Fig.  296, 
showing  exterior  and  section.  For  full  instructions,  see  page  598. 

For  a  lift  of    5  ft.,  15  Ibs.  steam  pressure  is  required. 

*»        "         10  "     20    "        <4  "  u 

*'        «         15  u     25    4k        "  u  4t 

u        **         20  u     35    "        u  u  " 

u        "         25  u     45    "        u  u  u 

Operation*  —  Open  overflow  valves  Nos.  1  and  3  ;  close  forcer 
steam  valve  No.  2  and  open  the  starting  valve  in  the  steam  pipe. 
When  the  water  appears  at  the  overflow,  close  No.  1  valve ;  open 
No.  2  valve  one-quarter  turn  and  close  No.  3  valve.  The  inspir- 
ator will  then  be  in  operation. 

NOTE.  —  No.  2  valve  should  be  closed  with  care  to  avoid  damag- 
ing the  valve  seat.  When  the  inspirator  is  not  in  operation,  both 
overflow  valves  Nos.  1  and  3  should  be  open  to  allow  the  water  to 
drain  from  it.  No  adjustment  of  either  steam  or  water  supply  is 
necessary  for  varying  steam  pressures,  but  both  the  temperature 
and  quantity  of  the  delivery  water  can  be  varied  by  increasing  or 
reducing  the  water  supply.  The  best  results  will  be  obtained 
from  a  little  experience  in  regulating  the  steam  and  water  supply. 
If  the  suction  pipe  is  filled  with  hot  water,  either  cool  off  both  it 
and  the  inspirator  with  cold  water,  or  pump  out  the  hot  water  by 
opening  and  closing  the  starting  valve  suddenly.  To  locate  a  leak 
in  the  suction  pipe,  plug  the  end,  fill  it  with  water,  close  No.  3 
valve  and  turn  on  full  steam  pressure.  Examine  the  suction  pipe 
and  the  water  will  indicate  the  leak.  If  the  inspirator  does  not 
lift  the  water  properly,  see  if  there  is  a  leak  in  the  suction  pipe. 
Note  if  the  steam  pressure  corresponds  to  the  lift  as  above  speci- 
fied, and  if  the  sizes  of  pipe  used  are  equal  in  size  to  inspirator 
connections.  If  the  inspirator  will  lift  the  water,  but  will  not  de- 
liver it  to  the  boiler,  see  if  the  check  valve  in  the  delivery  pipe  is 


598 


HANDBOOK    ON     ENGINEERING. 


in  working  order  and  does  not  u  stick."  Air  from  a  leak  in  the 
suction  connections,  will  prevent  the  inspirator  from  delivering 
the  water  to  the  boiler,  even  more  than  it  will  in  lifting  it  only.  If 
No.  1  valve  is  damaged,  or  leaks,  the  inspirator  will  not  work 
properly.  No.  1  valve  can  be  easily  removed  and  ground. 


STtAM 


Feed  to 
Boiler. 


Suction. 


Overflow. 

ISP 

3 
Fig.  296.    Hancock  inspirator. 

To  remove  scale  and  deposits  from  inspirator  jets  or  parts, 
disconnect  the  inspirator  and  plug  both  the  suction  and  delivery 
outlets  with  corks.  Open  No.  2  valve  and  fill  the  inspirator  with 
a  solution  of  one  part  muriatic  acid  and  ten  parts  water0  Allow 
this  solution  to  remain  in  the  inspirator  over  night,  then  wash  it 
thoroughly  in  clear  water. 

NOTE.  —  It  is  not  generally  necessary  to  return  an  inspirator 
for  repairs.  The  repair  parts  required  can  be  ordered  and  the 
inspirator  readily  put  in  order. 


.HANDBOOK   ON   ENGINEERING.  599 

TO   DISCOVER  CAUSE   OF   DIFFICULTIES. 

WHEN    INJECTOR    FAILS    TO    GET    THE    WATER. 

1.  The  supply  may  be  cut  off  by :   (a)  Absence  of  water  at  the 
source,     (b)  Strainer  clogged  up.     (c)  The  suction  pipe,  hose 
or  valve  stopped  up ;  or  if  a  hose  is  used,  its  lining  may  be  loose 
(a  frequent  cause  of  trouble). 

2.  A  large  leak  in  the  suction  (note  that  a  small  leak  will  pre- 
vent injector  from  working,  but  not  from  getting  the  water). 

3.  Suction   pipe   or    water   very   hot.     Open    drip-cock,  turn 
steam  on  slowly,  then  shut  it  off  quickly.     This  will  cause  the 
cool  air  to  rush  into  the  suction  pipe  and  cool  it  off.     Repeat  if 
necessary. 

4.  Lack  of  steam  pressure  for  the  lift ;  or,  in   some  instances, 
too  much  steam  pressure.     If  the  steam  pressure  is  very  high,  the 
injector  will  get  the  water  more  readily  if  the  steam  is  turned  on 
slowly  and  the  drip-cock  left  open  until  the  water  is  got. 

IF     THE     INJECTOR     GETS    THE    WATER    BUT    DOES    NOT    FORCE    IT    TO 

THE    BOILER. 

1.  No   globe  valve  on  the  suction  with  which  to  regulate  the 
water,  or  else  the  supply  water  not  properly  regulated. 

2.  Dirt  in  delivery  tube. 

3.  Faulty  check  valve. 

4.  Obstruction  between  inj.ector  and  check  valve,  or  between 
check  valve  and  boiler. 

5.  Small    leak  in  suction  pipe  admitting  air   to   the   injector 
along  with  the  supply  water.     It  is  ten  to  one  this  is  the  cause  of 
the  difficulty  every  time. 

6.  Be   sure  and  understand  the  directions  for  starting  before 
condemning  the  injector. 


600  HANDBOOK    ON    ENGINEERING. 

U.  S.  INJECTOR. 

IF    THE    INJECTOR    STARTS    BUT  "BREAKS." 

1.  Supply  water  not  properly  regulated.     If  too  much   water, 
the  waste  or  overflow  will  be  cool ;  if  too  little,  the  water  will  be 
very  hot. 

2.  Leaky  supply  pipe  admitting  air  to  the  injector.     It  is  ten 
to  one  this  is  the  cause  of  difficulty.     The  suction  must  be  air 
tight ;  test  as  directed. 


Fig.  297.    Showing  the  U.  S.  injector  and  pipe  connections. 
8.  Dirt  or  other  obstruction,  such  as  lime,  etc.,  in  delivery  tubet 
4.  Connecting  steam  pipe  to  pipe  conducting  steam  to  other 
points  besides  the  injector,  er  not  having  suction  pipe  independent. 


HANDBOOK    ON    ENGINEERING. 


601 


5.  Sometimes  a  globe  valve  is  used  on  the  suction  connection 
that  has  a  loose  disc,  and  after  starting  the  disc  is  drawn  down^ 
thus  partially  closing  the  valve;  it  is,  of  course,  equivalent  to 
giving  the  injector  too  little  water.  To  remedy  this,  take  the 
globe  valve  off  and  reverse  it  end  for  end. 

To  clean*  —  To  clean  injector,  unscrew  plug  0,  and  the  re- 
movable jet  inside  resting  in  it  will  follow  the  plug  out. 
.  Turn  on  steam  (not  less  than  forty  pounds)  and  all  dirt  will  be 
blown  out.  Examine  all  passages  and  drill  hole's  and  see  that  no 
dirt  or  scale  has  lodged  in  them.  Replace  jet  by  setting  it  in  the 
plug  (which  acts  as  a  guide)  and  screw  into  place  tightly.  Be 
careful  not  to  bruise  any  jets,  and  use  no  wrenches  on  body  of 
injector. 

SIZES  AND  CAPACITIES  OF  U.  S.  INJECTOR. 


SIZE. 

ALL  PIPE 
CONNECTIONS. 

CAPACITY 
GALLONS  PER  HOUR. 

HORSE  POWER. 

MAX. 

MIN. 

oo     ...  

lj 

1 
1 
1J 
If 
l| 
H 

2 
2 
2 
2} 

2j 

n. 

36 
65 
90 
125 
170 
250 
340 
475 
575 
750 
9'20 
1350 
1750 
2275 
2820 
3400 
3650 
4000 

15 

28 
40 
60 
75 
125 
'      140 
250 
300    ' 
350 
450 
675 
850 
1000 
1300 
1700 
1800 
1950 

1  t 

3 

6 

8 
15 
20 
30 
40 
60 
70 
85 
120 
165 
230 
295 
375 
460 
500 

0      4 

8 
10 
15 
20 
30 
40 
60 
70 
95 
120 
165 
230 
295 
375 
460 
500 
600 

o 

i      

2  

3             

4  .. 

5  

6  .. 

7 

8  .. 

9          

10... 

11 

12 

13     . 

14 

15  .. 

16        

To  test  for  leaks.  — Plug  up  end  of  water  supply  pipe,  then 
fit  a  piece  of  wood  into  cap  Z,  so  that  when  screwed  down  it  will 
hold  check  valve  in  place,  then  turn  on  steam  and  it  will  locate 
leak.  Do  not  fail  to  do  this  in  case  of  any  trouble. 

TO    START    AND    STOP    INJECTOR. 

To  start* — Open  full  the  globe  valve  in  water  supply  first, 
and  then  globe  valve  in  steam  pipe  wide  open.  If  water  issues 
from  overflow,  throttle  the  valve  //  until  discharge  stops.  Reg- 


602 


HANDBOOK    ON    ENGINEERING. 


ulate  injector  with  water  supply  valve,  not  by  steam  valve. 
When  water  supply  is  above  the  injector,  in  starting  open  steam 
valve  first. 

To  stop* — Close  the  steam  valve.  The  water  valve  H  need 
not  be  closed  unless  the  injector  is  used  as  a  non-lifter,  or  lift  is 
considerable. 


PRICE  LIST,  CAPACITY,  HORSE  POWER,  ETC.  OF  PENBERTHY 

INJECTOR. 


Size. 

Price. 

Pipe  Connections. 

Capacity  per  Hour. 
1  to  4  ft  lift,  50  to  75 
Ibs.  Pressure. 

Horse 
Power. 

GO. 
A  

$16  00 
18  00 

Steam.   Suet 

2*              2 
2                2 

ion.    De 

1 

1< 

1 
2 
2 

iv 
|  i( 

; 

. 

cry, 

D. 

Maximt 
80  g 
120 
165 
250 
340 
475 
575 
750 
920 
1300 
1740 
2270 
2820 

m. 

al. 

Minlmu 
55  g 
70 
90 
135 
165 
300 
350 
4  0 
500 
700 
900 
1100 
1400 

m. 
al. 

4  to     8 
8  to    10 
10  to    15 
15  to    25 
25  to    35 
35  to    50 
50  to    60 
60  to     95 
95  to  162 
120  to  150 
165  to  230 
230  to  2:>() 
290  to  365 

A  A  
B    

20  00 
25  00 

BB 
C  .. 
CC. 
D... 

E   . 
EK 
F    . 
FF. 

30  00 
40  00 
45  00 
55  00 
60  00 
75  00 
90  00 
110  00 
125  00 

HANDBOOK    ON    ENGINEERING.  603 

To  find  the  number  of  gallons  of  water  delivered  by  a  steam 
pump  in  one  minute,  when  the  diameter  and  stroke  of  water 
piston,  and  the  number  of  strokes  per  minute  are  given :  — 

Rule*  —  Square  the  diameter  of  water  piston  and  multiply  the 
result  by  .7854.  Multiply  this  product  by  the  stroke  of  the 
water  piston  in  inches ;  and  multiply  this  product  by  the  number 
of  strokes  per  minute,  and  divide  the  result  by  231. 

Example*  —  How  many  gallons  of  water  per  minute  will  a 
steam  pump  deliver,  whose  water  cylinder  is  6  inches  in  diameter 
and  12  inches  stroke,  making  60  strokes  per  minute? 

Ans.  88.128  galls. 

Operation  :  6  X  6  X  .7854       28.2744. 

28.2744  X  12  X  60 
And,  ~iar~         -  =  88-128- 

To  find  the  relative  proportion  between  the  steam  and  water 
pistons. 

Rule* —  Multiply  the  area  of  the  pump  piston  by  the  resistance 
of  the  water  in  pounds  per  square  inch ;  and  divide  the  product 
by  the  pressure  of  steam  in  pounds  per  square  inch.  The  quotient 
will  give  the  area  of  steam  piston  in  square  inches  to  balance  the 
resistance.  To  this  quotient  add  from  30  to  100  per  cent  of  it- 
self,—  depending  on  the  speed  of  the  pump,  —  and  divide  the 
sum  by  .7854,  and  extract  the  square  root  of  the  quotient  for  the 
diameter  of  the  steam  piston. 

Example*  —  What  should  be  the  diameter  of  the  steam  piston 
to  force  water  against  a  pressure  of  125  pounds  per  square  inch, 
the  diameter  of  water  piston  being  6  ins.  and  the  steam  pressure 
60  Ibs.  per  square  inch?  Ans.  10 J  inches. 

Operation:  6  X6  X  .7854  =  28.2744  sqr.  ins. 

And,  28.2744  X  125  ^=  3534.3  pounds  the  total  resistance. 

3534.3 
Then,   ~~ —  =  58.9   square  inches  the  area  of  steam  piston. 


004  HANDBOOK    ON    ENGINEERING. 

We  will  add  50  per  cent  for  friction  in  pump  and  in  delivery 
pipe,  and  for  a  moderate  speed  of  pump. 
Then,  58.9  X  .50  =  29.45. 
And,  58.9  +  29.45=88.35. 

88.35 
And,    -TT    =  112.49  sqr   iris. 


Then,  y  112.49  =  10.6  ins.  the  diameter  of  the  steam  piston. 

To  find  the  pressure  against  which  a  pump  can  deliver  water, 
when  the  diameter  of  steam  piston,  pressure  of  steam  in  pounds 
per  square  inch,  and  diameter  of  water  piston  are  given :  — 

Rule*  —  Multiply  the  area  of  steam  piston  by  the  pressure  of 
steam  in  pounds  per  square  inch,  and  divide  the  product  by  the 
area  of  the  pump  piston,  and  deduct  from  30  to  50  per  cent  for 
friction  in  the  delivery  pipe  and  in  the  pump  itself. 

Example* — The  area  of  the  steam  piston  is  112  square  inches, 
and  the  area  of  water  piston  is  28  square  inches,  and  the  steam 
pressure  is  60  Ibs.  per  square  inch,  against  what  pressure  can  the 
pump  deliver  water,  the  resistance  from  friction  being  48  per  cent? 

Ans.  125  Ibs.  per  sqr.  in.,  nearly. 

112X60 
Operation:  — 28 —  ~  24:0* 

And,  240  X  -48  =  115.20. 
Then,  240  —  115.20  =  124.8. 

To  find  the  steam  pressure  required  when  the  diameter  of  the 
steam  piston,  the  diameter  of  the  water  piston,  and  the  resistance 
against  the  pump  in  pounds  per  square  inch  are  given :  — 

Rule, —  Multiply  the  area  of  water  piston  by  the  resistance  on 
the  pump  in  pounds  per  square  inch,  and  divide  the  product  by 
the  area  of  the  steam  piston. 


HANDBOOK    ON   ENGINEERING.  605 

Example*  —  The  resistance  against  the  pump,  including  fric- 
tion, is  240  pounds  per  square  inch.  The  area  of  steam  piston 
is  112  square  inches,  and  the  area  of  water  piston  is  28  square 
inches.  What  pressure  of  steam  is  required  to  operate  the  pump  ? 

Ans.  60  Ibs.  per  sqr.  in. 

-  240  X  28 

Operation:  —  —  —  =60. 

Now  anything  over  60  Ibs.  will  operate  the  pump,  and  the  faster 
it  is  run  the  higher  must  be  the  pressure  above  60  pounds. 

To  find  the  diameter  of  water  piston  when  the  diameter  of 
steam  piston,  the  steam  pressure  in  pounds  per  square  inch,  and 
the  resistance  against  the  pump  piston  in  pounds  per  square  inch 
are  given  :  — 

Rule*  —  Multiply  the  area  of  steam  piston  in  square  inches  by 
the  steam  pressure  in  pounds  per  square  inch,  and  divide  the 
product  by  the  resistance  in  pounds  per  square  inch  on  the  water 
piston. 

Example*  —  The  resistance  against  the  pump,  including  fric- 
tion, is  240  pounds  per  square  inch  ;  the  area  of  steam  piston  is 
112  square  inches,  the  steam  pressure  is  60  pounds  per  square 
inch,  what  should  be  the  diameter  of  water  piston? 

Ans.  6  inches. 

Operation  j  112X6-°  =  35.65  sqr.  ins.        Call  it  36  sqr.  ins. 


Then,  ^W  =  6. 

To  find  the  horse  power  required  in  a  steam  pump  to  feed  a 
boiler  with  a  given  number  of  pounds  of  water  per  hour  against  a 
given  pressure  of  steam  :  — 

Rule*  —  Multiply  the  velocity  of  flow  of  water  in  feet  per  min- 
ute by  the  total  pressure  against  which  the  water  is  pumped  in 
pounds  per  square  incL,  and  divide  the  product  by  33,000,  and 
the  quotient  will  be  the  horse  power. 


606  HANDBOOK    ON    ENGINEERING. 

Example*  —  What  horse  power  is  required  to  feed  a  boiler 
with  600  gallons  of  water  per  hour  against  a  total  resistance  of 
112  IbSo  per  square  inch,  including  the  friction  in  the  delivery 
pipe,  lift  of  water  in  suction  pipe,  weight  of  check  valve,  and 
friction  in  the  pump  itself?  Ans.  1  H.  P»  nearly. 

Operation:  600  X  231  =  138,600  cubic  inches  of  water  per 
hour. 

138,600 
And,      —  TiTj  —  =  2310  cubic  inches  of  water  per  minute. 

2310 
And,    —rg—  =192.5    feet     per   minute  >    the   velocity   of  the 

water  o 

The  total  resistance  is  112  Ibs.  per  sqr.  in0 
Then,  192.5  X  112  =  21560  foot  pounds. 

21560 
And'     3^000  =  -6"H.P. 

Now  add  say  50  per  cent  and  we  have  .653  X  .50  =.3265. 
And,  .653  +  .3265  =  .9795. 

This  pump  will  feed  a  boiler  as  shown  above,  or  it  will  deliver 

600  gallons  of  water  per  hour  under  a  head  of  258  feet. 
&  ^ 

112 
Thus, 


To  find  the  horse  power  of  boiler  required  to  furnish  steam  for 
a  pump  running  at  its  fullest  capacity. 

Rule*  —  Multiply  the  number  of  gallons  of  water  delivered  by 
the  pump  in  one  minute  by  8£.  Multiply  this  product  by  the 
total  height  in  feet  to  which  the  water  is  to  be  lifted,  measuring 
vertically  from  the  source  of  supply  to  the  point  of  delivery,  and 
divide  the  result  by  33,000.  Add  from  50  to  75  per  cent  to  the 
quotient  for  loss  from  friction  of  water  in  the  pipe,  friction  in 
the  pump,  waste  of  steam  in  the  cylinder,  and  other  contingencies, 
and  the  result  will  give  the  horse  power  of  boiler  required. 


HANDBOOK   ON    ENGINEERING.  607 

Example*  —  What  horse  power  of  boiler  is  required  to  run  a 
steam  pump  lifting  800  gallons  of  water  per  minute  to  a  height  of 
163  ft.  from  the  source  of  supply?  Ans.  50  H.  P.,  nearly. 

Operation  :  800  X  8£  =  6667  Ibs.  of  water. 

And,  6667  X  163  =  1,086,721  footpounds. 
1,086,721 

And'    -337000-  =33H'P-'  near1^' 

Then,  33  X  .50  =  16.50. 

And,  33  +  16.5  =  49.5. 

To  find  the  diameter  of  discharge  nozzle  for  a  steam  pump, 
when  the  diameter  and  stroke  of  the  water  piston  and  the  number 
of  strokes  per  minute  are  given,  and  the  maximum  flow  of  water 
in  feet  per  minute  is  given  :  — 

Rule.  —  Find  the  cubic  contents  of  the  water  cylinder  for  one 
stroke  in  cubic  feet,  and  multiply  it  by  the  number  of  strokes  per 
minute.  Multiply  this  product  by  144  and  divide  the  result  by 
the  velocity  of  the  water  in  feet  per  minute,  and  the  quotient  will 
be  the  area  of  pump  nozzle  in  square  inches. 

Example*  —  The  diameter  of  water  cylinder  is  10  inches,  and 
the  stroke  of  piston  is  12  inches,  and  the  speed  is  50  strokes  per 
minute.  The  velocity  of  water  required  is  500  feet  per  minute, 
what  should  be  the  diameter  of  pump  discharge  nozzle? 

Ans.  3J  ins.,  nearly. 

Operation:  10  X  10  X  .7854  =  78.54  sqr.  ins.  area  of  piston. 

And,  78.54  X  12  =  942.48  cubic  inches  in  the  cylinder  for  one 
stroke. 

And,  '      =  .5454  of  a  cubic  foot  for  one  stroke. 


And,  .5454  X  50  =  27.27  cubic  feet  for  50  strokes  per  minnte. 

27  27  X  144 
Then,   -    ""XnrT    ~~  ==  7-853?  s(lr'  ins'  tlie  area  of  tlie 


\1^1  =  3. 
\.7854 


And,  =  3.1  ins.  the  diameter. 


608  HANDBOOK    ON    ENGINEERING. 

Xo  find  the  approximate  size  of  suction  pipe  when  its  length 
does  not  exceed  25  ft.  and  when  there  are  not  more  than  two 
elbows  in  the  same  :  — 

Rule*  —  Square  the  diameter  of  water  cylinder  in  inches  and 
multiply  it  by  the  speed  of  the  piston  feet  in  per  minute  ;  divide 
this  product  by  200,  and  divide  this  quotient  by  .7854  and 
extract  the  square  root,  and  the  result  will  be  the  diameter  of 
suction  pipe,  except  for  very  small  pipes  when  it  should  be  made 
larger  than  the  size  given  by  the  rule,  in  order  to  lessen  the  friction 
of  the  moving  water. 

Example*  —  The  diameter  of  water  cylinder  is  6  ins.,  the  stroke 
of  piston  is  12  ins.,  and  the  number  of  strokes  per  miuuteis  60, 
what  should  be  the  diameter  of  suction  pipe?  Ans.  4  ina» 


And,  i|i=  ,3.75. 


Then,  «J13.75  =  3.7  ins.  There  is  no  pipe  of  this  size  made, 
BO  take  4-inch  pipe. 

To  find  the  velocity  in  feet  per  minute  necessary  to  discharge 
a  given  number  of  gallons  of  water  per  minute  through  a  straight 
smooth  iron  pipe  of  a  given  diameter,  regardless  of  friction  :  — 

Rule*  —  Reduce  the  gallons  to  cubic  feet  and  multiply  by  144, 
and  divide  the  product  by  the  area  of  the  pipe  in  square  inches. 

Example*  —  What  should  be  the  velocity  of  the  water  to  dis- 
charge 100  gallons  of  water  per  minute  through  a  4-inch  pipe? 

Ans.   149  ft.  per  minute. 

Operation  j  —  -£-  —  =13  cubic  feet. 


And,  13  X  144  —  1872  cubic  inches  placed  in  a  continuous 
line. 

Then,  4  X  4  X  -7854  =  12.5664  square  inches,  the  area  of 
pipe. 


And,  _== 

12.5664 


HANDBOOK    ON    ENGINEERING.  609 

To  find  the  velocity  in  feet  per  minute  of  water  flowing  through 
a  pipe  of  given  diameter,  when  the  diameter  of  water  cylinder  and 
speed  of  piston  in  feet  per  minute  are  given  :  — 

Rule*  —  Multiply  the  area  of  water  cylinder  in  square  inches 
by  the  piston  speed  in  feet  per  minute,  and  divide  the  product  by 
the  area  of  the  pipe  in  square  inches. 

Example*  —  The  diameter  of  water  cylinder  is  8  ins.,  and  the 
piston  speed  is  100  ft.  per  minute,  and  the  diameter  of  discharge 
pipe  is  4  ins.,  what  is  the  velocity  of  the  water  in  the  discharge 
pipe?  Ans.  400  ft.  per  minute. 

Operations  8  X  8  X  .7854  =  50.26  sqr.  ins.  area  of  the 
water  piston. 

And,  50.26  X  100  =  5026. 

The  area  of  the  pipe  is  12.56  sqr.  ins. 


Then,  =-.  400. 

'    12.56 

To  find  the  number  of  gallons  of  water  discharged  per  minute 
through  a  circular  orifice  under  a  given  head  :  — 

Rule*—  Find  the  velocity  of  discharge  in  feet  per  second  and 
multiply  it  by  60,  then  multiply  this  product  by  the  area  of  the 
orifice  in  square  feet,  and  multiply  this  last  product  .by  7.48,  and 
the  result  will  be  the  gallons  discharged  per  minute. 

Example.  —  How  many  gallons  of  water  will  be  discharged  per 
minute  through  an  orifice  4  inches  in  diameter  under  a  head  of  81 
feet?  Ans.  2829.7  galls. 

Operation:  «J81  =  9.  And,  9  X  8.025  =  72.225  feet  per 
second,  the  velocity  of  discharge.  The  factor  8.025  is  a  con- 
stant for  any  head,  and  is  found  thusly:  — 


v'2  X32.2  =8.025. 

Or,  the  velocity  of  discharge  may  be  found  in  this  manner ;  — 
y2  X  82.2  X  81  =  72.22  feet  per  second,  that  is,  the  veloc- 
ity in  feet  per  second  equals  the  square  root  of  the  acceleration 

39 


610  HANDBOOK    ON    ENGINEERING. 

due  to  gravity  multiplied  into  the  head  in  feet.     Continuing  the 
operation,  we  have :  — 

72.225  X  60  =  4333.5  feet  per  minute. 

And,  4  X  4  X  -7854  =  12.5664  sqr.  ins.  area  of  orifice. 

And,   — =  .0873   of  a  square  foot,  the  area  of  orifice. 

144 

also. 

Then,  4333.5  X  -0873  =  378.3  cubic  feet. 

And,  378.3  X  7.48  =  2829.7  galls. 

NOTE.  —  With  a  ring  orifice  only  64  per  cent  of  the  above 
amount  of  water  would  be  discharged,  and  with  a  funnel-shaped 
orifice  only  82  per  cent. 

To  find  the  number  of  gallons  of  water  discharged  per  minute 
under  a  given  pressure  in  pounds  per  square  inch :  — 

Rule*  —  Divide  the  given  pressure  in  pounds  per  square  inch 
by  .433  in  order  to  get  the  head  in  feet,  and  then  proceed  accord- 
ing to  the  foregoing  rule. 

Example* — •  How  many  gallons  of  water  will  be  discharged  per 
minute  through  an  orifice  one  square  inch  in  area,  under  a  pres- 
sure of  35.073  Ibs.  per  square  inch?  Ans.  81  galls,  per  minute. 

35.073 
Operation:      4oo     —81  ft.,   head   equivalent   to   the   given 

pressure. 

And,  >/2  X  32.2  X81  =  72.225  ft.  per  second  the  velocity. 
And,  72.225  X  60  =  4333.5. 

Also,     rrr  =  .00694  of   a  square  foot,  equals  the  area  of  the 

orifice. 

And,  4332.5  X  .00694  =.30.07449. 
And,  30.07449  X  7.48  =  224.9  galls. 
Then,  deducting  64  per  cent,  we  have:  — 
224.9  X  .64=  143.9. 
And,  224.9  —  143.9  =81. 


HANDBOOK   ON    ENGINEERING.  611 

To  find  the  area  of  orifice  in  square  ins.  necessary  to  discharge 
a  given  number  of  gallons  of  water  per  minute  under  a  given 
head  in  feet  :  — 

Rule*  —  Divide  the  number  of  gallons  by  the  constant  number 
15.729  multiplied  into  the  square  root  of  the  head,  and  the  result; 
will  be  the  area  of  orifice  in  square  inches. 

Example*  —  What  must  be  the  area  of  orifice  to  discharge 
1778.5  gallons  of  water  per  minute  under  a  head  of  81  feet? 

Ans.   12.56  sqr.  ins. 

Operation:  >/8T  =  9. 


And,  9  X  15.  729  =  141.6. 

1778.5 
Then,  —  —  =12,56. 

To  find  how  many  gallons  of  water  will  flow  through  a  straight 
smooth  iron  pipe  in  one  minute  under  a  given  pressure  in  pounds 
per  square  inch,  or  head  in  feet  :  — 

Rule*  —  Multiply  the  inside  diameter  of  the  pipe  in  feet  by  the 
head  in  feet,  and  divide  the  product  by  the  length  of  pipe  in  feet. 
Extract  the  square  root  of  the  quotient  and  multiply  it  by  48, 
and  the  product  will  be  the  velocity  of  flow  in  feet  per  second. 
Multiply  this  result  by  12  to  reduce  it  to  inches,  and  by  60  for 
the  flow  per  minute,  and  multiply  again  by  the  area  of  the  pipe  in 
square  inches,  and  divide  by  231  for  the  gallons  discharged  per 
minute. 

Example*  —  How  many  gallons  of  water  will  be  discharged  per 
minute  through  a  4-inch  pipe  2000  feet  long,  under  a  head  of  92 
feet?  Ans.  230  galls,  per  minute, 

Operation  :  4  ins.  =  .33  of  a  foot. 

And,  92  X  .33  =  30.36. 

30.36 
And'    2000" 


12  HANDBOOK   ON   ENGINEERING  . 

And,  V^l5  =.1225. 

Then.  .1225  X  48  X  12  =  70.56  ins.  per  second. 

And,  70.56  X  60  =4233.60  ins.  per  minute. 

Then,  4  X  4  X  .7854  =  12.56  sqr.  ins.  the  area  of  the  pipe. 

And,  4233.60  X  12.56  =53174.016  cubic  ins. 

53174.016 
Then,  —      --  =  230.2. 


Example.  —  Assume  two  wells  A  and  B  with  their  mouths  on 
a  level.  Well  A  is  26  ft.  deep,  and  well  B  is  40  ft.  deep.  Well 
A  is  fed  by  natural  springs  and  has  a  depth  of  water  of  5  feet. 
The  distance  between  the  wells  is  600  feet.  How  many  gallons 
of  water  will  a  1  inch  pipe,  laid  perfectly  straight  and  level, 
syphon  over  in  one  minute  providing  well  B  is  always  pumped 
dry,  and  that  the  pipe  extends  into  well  A  26  feet,  and  into  well 
B  38  feet,  using  bends  instead  of  elbows? 

Ans.  4  galls,  per  minute. 

Operation.  —  The  head  equals  38  feet. 
The  diameter  of  the  pipe  equals  .0833  foot. 
Then,  600  +  38  +  26  =  664  ft.  total  length  of  pipe. 
And,  38  X  -0833  =  3.1654. 

3.1654 
And, 


And,  V  .0047  =  .068. 

Then,  .068  X  48  =  3.264  ft.  velocity  per  second. 
And,  3.264  X  60  =  195.840  ft.  velocity  per  miD. 
The  area  of  pipe  equals  .7854  sqr.  inch. 
Then,  195.840  X  .7854  =  153.8127. 
And,  153.8127X7.48  =  1150.52. 

1150.52 
And,    — ^-JT —  =  8  nearly,  gallons. 


HANDBOOK  .ON    ENGINEERING.  613 

Deducting  50  per  cent  on  account  of  2  bends  and  friction,  we 
have  4  gallons  per  minute  syphoned  over. 

To  find  the  head  in  feet  due  to  friction  in  a  pipe  running 
full :  - 

Rule*  —  Multiply  the  length  of  the  pipe  in  feet  by  the  square 
of  the  number  of  gallons  per  minute,  and  divide  the  product  by 
1,000  times  the  5th  power  of  the  diameter  of  the  pipe  in  inches. 
The  quotient  less  10  per  cent  is  the  head  in  feet  necessary  to  over- 
come the  friction. 

NOTE.  —  The  head  is  the  vertical  distance  from  the  surface  of 
the  water  in  the  tank  or  reservoir,  to  the  center  of  gravity  of  the 
lower  end  of  the  pipe,  when  the  discharge  is  into  the  air,  or,  to 
the  level  surface  of  the  lower  reservoir  when  the  discharge  is  under 
the  water. 

Example*  —  A  2-inch  pipe  100  feet  long  and  running  full, 
discharges  50  gallons  of  water  per  minute,  what  is  the  head  in 
feet  due  to  friction?  Ans.  7.029  feet. 

Operation :  2  X  2  X  2  X  2  X  2  =  32  =  the  5th  power  of  the 
diameter  of  the  pipe. 

And,  50  X  50  =  2500. 
And,  2500  X  100  =  250,000. 
Also,  32  X  1,000  =  32,000. 

Then>  iw  =  7'81- 

And,  7.81  less  10  percent  of  itself  equals  7.029. 
The  resistance  to  the  flow  of  water  in  pounds  per  square  inch> 
due  to  friction,  is  found  by  dividing  the  friction  head  by  2.3. 

7.029 
Thus,    ^-^g-  =  3.051bs. 

To  find  the  size  of  pump  required  to  feed  a  boiler  of  a  given 
capacity :  — 


614  HANDBOOK    ON    ENGINEERING. 

Rule* — Multiply  the  number  of  pounds  of  water  evaporated 
per  pound  of  coal  by  the  number  of  pounds  of  coal  burned  per 
sqr.  foot  of  grate  surface  per  hour,  and  multiply  this  product  by 
the  number  of  square  feet  of  grate  surface  in  the  boiler  furnace. 
This  will  give  the  number  of  pounds  of  water  evaporated  by  the 
boiler  in  one  hour.  Divide  this  by  60  to  find  the  evaporation  per 
minute,  and  divide  again  by  8|  in  order  to  get  the  evaporation  in 
gallons  per  minute  ;  add  from  10  to  15  per  cent  to  the  last  result 
for  leakage  and  other  contingencies,  and  select  a  pump  that  will 
deliver  the  gross  number  of  gallons  of  water  per  minute  at  any 
speed  that  may  be  desired,  usually  taken,  however,  at  fifty  feet 
per  minute. 

Example*  —  What  should  be  the  dimensions  of  the  water  end 
of  a  steam  pump,  and  what  should  be  the  speed  of  piston  to  sup- 
ply a  boiler  having  a  grate  surface  of  20  square  feet,  and  burning 
15  pounds  of  coal  per  square  foot  of  grate,  and  evaporating  9 
pounds  of  water  per  pound  of  coal  per  hour? 

Operation:  20  X  15  X  9  =2700  pounds  of  water  evapo- 
rated per  hour. 

2700 

And,  =  45  Ibs.  of  water  evaporated  per  minute. 

60 

And,  -—  =  5.4  galls,  per  minute. 

Then,  5.4  plus  10  per  cent  of  itself,  equals  6  galls,  nearly  per 
per  minute. 

Referring  to  a  pump  maker's  catalogue  we  find  that  a  single 
pump  3£"  X  2J"  X  5",  making  90  strokes  per  minute,  will  do 
the  work,  or,  a  duplex  pump  3"  X  2"  X  3",  making  100  strokes 
per  minute  will  do  the  work  equally  as  well.  Again,  adding  10 
per  cent  to  the  pounds  of  water  evaporated  per  minute  we  have, 
45  +  4.5  =49.5  pounds.  And,  49.5  X  27.71  =  1371.64  cubic 
inches  displacement  in  the  water  cylinder  per  minute,  and  at  90 
strokes  per  minute  we  have  15.24  cubic  inches  displacement  per 
stroke. 


HANDBOOK  .Off    ENGINEERING.  615 

Thus,   1371*64  =  15.24,  which  is  all  that  is  required  for  our 

yo 

boiler. 

Now,  taking  the  above  single  pump  we  have:  2.25  X  2.25  X 
.7854  X  5  =  19.8  cubic  inches  displacement  per  stroke.  And, 
taking  the  duplex  pump  we  have:  2  X  2  X  .7854  X  3  X  2  = 
18.8  cubic  ins.  displacement  for  each  double  stroke  of  the  piston, 
or,  plunger,  showing  that  either  pump  is  of  ample  capacity  to 
feed  the  boiler  at  a  fair  piston  speed. 

To  find  the  duty  of  a  pumping  engine  when  the  number  of 
pounds  of  coal  burned,  the  number  of  gallons  of  water  pumped, 
the  pressure  in  pounds  per  square  inch  against  which  the  pump 
piston  works,  and  the  height  of  suction  are  given :  — 

Rule*  —  Find  the  head  in  feet  against  which  the  pump  works, 
by  multiplying  the  pressure  by  2.3,  add  the  suction  in  feet 
to  this  head  in  order  to  get  the  total  head.  Multiply  the 
gallons  of  water  by  8J  to  get  the  pounds  of  water  deliv- 
ered. Then  multiply  the  total  number  of  pounds  of  water 
by  the  head  in  feet,  and  divide  the  product  by  the  number  of 
pounds  of  coal  divided  by  100,  and  the  result  will  give  the  duty 
in  foot  pounds.  The  duty  of  a  pumping  engine  is  the  number  of 
pounds  of  water  raised  one  foot  high  for  each  100  pounds  of  coal 
burned. 

Example* —  What  is  the  duty  of  an  engine  pumping  2,890,000 
gallons  of  water  in  12  hours  against  a  pressure  of  30  pounds  per 
sqr.  inch,  the  suction  being  12  feet,  and  coal  burned  24,470 
pounds?  Ans.  8,070,426  foot  pounds. 

Operation:  30  X  2.3  =  70  nearly  the  head  in  feet. 

And,  2,890,000  X  8£  ==  24,083,333  pounds  of  water. 

Also,  70  +  12  =  82  ft.  total  lift  of  water. 

And,  24,083,333  X  82  =  1,974,833,306  Ibs.  of  water  lifted 
one  foot  high  in  12  hours. 

Then,  ^=,244.7. 


616  HANDBOOK    ON    ENGINEERING. 

And)  1,974888806  =  8>070>426. 

To  find  the  horse  power  of  a  pumping  engine  :  — 

Rule*  —  Divide  the  number  of  pounds  of  water  raised  one  foot 
high  in  one  minute  by  33,000. 

Example*  —  What  is  the  H.  P.  of  the  pumping  engine  given 
in  the  above  example?  Ans.  83.11  H.  P. 

Operation:  12  X  60  =  720  minutes. 

And,  1'974'833'8Q6  ==  2,742,824  Ibs.  of  water  raised  one  foot 

7  &0 

high  in  one  minute  0 


Then,      ''^  83.11. 
33,000 

To  find  the  capacity  of  a  pump  to  feed  a  boiler  it  is  necessary 
to  know  how  much  water  the  boiler  is  capable  of  evaporating  per 
minute  or  per  hour.  Each  horse  power  of  boiler  capacity  corre- 
sponds to  an  evaporation  of  thirty  pounds  of  water  per  hour.  It 
is  good  practice  to  operate  a  pump  slowly  and  continuously,  and 
for  this  reason  the  pump  running  at  its  normal  speed  should  be 
capable  of  supplying  about  twice  as  much  water  as  the  boiler 
evaporates  under  usual  conditions. 

To  find  the  diameter  of  water  cylinder  to  deliver  a  certain  num- 
ber of  gallons  of  water  per  minute,  when  the  stroke  of  the  piston 
and  the  number  of  strokes  per  minute  are  given  :  — 

Rule*  —  Multiply  the  number  of  gallons  by  231,  and  divide  the 
product  by  the  stroke  of  the  piston,  and  divide  this  quotient  by 
the  number  of  strokes  per  minute,  and  divide  this  last  quotient 
by  .7854,  then  extract  the  square  root  of  the  result  for  the 
diameter  of  the  water  piston. 

Example*  —  A  battery  of  boilers  evaporate  100,000  pounds  of 
water  in  one  hour,  what  should  be  the  diameter  of  water  cylinder 
to  supply  this  battery,  the  stroke  of  piston  being  12  inches  and 
making  100  strokes  per  minute?  Ans.  7  inches. 


HANDBOOK    ON    ENGINEERING.  617 

100,000 
Operation: ^Q — -=1666|   pounds  of  water  evaporated  in 

one  minute. 

L666| 
And,     '    Qt  '  =  200  galls,  evaporated    in  one    minute.     Then 

following  the  above  rule  we  have :  — 
200X231      =  46200. 

46200 
And,     -jg—  ^3850. 

3850 
And,    -J0JJ-    ^38.5. 

38.5 
And'    77854  ==49- 

Then,     j/49  =  7"  the  required  diameter. 

To  determine  the  H.  P.  of  boiler  a  steam  pump  of  given 
dimensions  will  supply  when  the  number  of  strokes  per  minute 
are  given :  — 

Rule*  —  Multiply  the  area  of  the  piston  is  square  inches  by  the 
stroke  of  piston  in  inches,  and  this  product  divided  by  231  will 
give  the  gallons  per  stroke.  Multiply  this  quotient  by  the  num- 
ber of  strokes  per  minute  for  the  number  of  gallons  per  minute, 
and  by  60  for  the  number  of  gallons  per  hour.  Multiply  this 
product  by  8^  to  find  the  number  of  pounds  of  water  per  hour 
deliA'ered  by  the  pump,  and  divide  this  product  by  30  for  the 
H.  P.  of  boiler  the  pump  will  supply.  This  rule  is  based  upon  the 
assumption  that  the  full  capacity  of  the  water  cylinder  is  deliv- 
ered at  each  stroke,  no  allowance  being  made  for  slippage,  leak- 
age, or  short  strokes. 

Example*  — •  The  water  piston  of  a  steam  pump  is  6  inches  in 
diameter  and  has  a  stroke  of  12  inches,  making  100  strokes  per 
Vfeinute,  what  H.  P.  of  boiler  will  the  pump  supply? 

Ans.  2448  H.  P. 


618  HANDBOOK    ON    ENGINEERING . 

Operation:  6  X  6  X  .7854  =28.2744  sqr.  ins.  area  of 
piston . 

And,     28.2744  X  12  =  339.2928  cubic  inches  for  one  stroke. 

339  2928 

And,     — i        -  —  1.4688  galls,  per  stroke. 
Z6 1 

And,     1.4688  X  100  =  146.88  galls,  per  minute. 

And,     146.88  X    60  =  8812.8  galls,  per  hour. 

And,    8812.8  X    8£  =  73,440  pounds  of  water  per  hour. 

73440 

Then,       Qn     =  2448  H.  P.  of  boilers. 
oU 

Watt  allowed  one  cubic  foot  (62£  Ibs.)  of  water  per  H.  P.  per 
hour.  Then  taking  this  allowance  instead  of  30  as  above,  we 

73440 

would  have,    go  -  =1175  H.  P.  of  boilers  which  the  above  pump 
b  J.O 

would  be  suitable  for,  and  which  could  be  run  very  slowly,  thus 
prolonging  the  life  of  the  pump. 

Even  though  a  suction  pipe  should  be  perfectly  air  tight,  a 
perfect  vacuum  cannot  be  formed  in  it,  because  water  contains 
air,  and  even  the  coldest  water  gives  off  some  vapor  tending  to 
impair  the  vacuum.  Twenty-eight  feet  is  a  very  good  lift  for  a 
pump  taking  its  water  by  suction. 

Pnmp  Formulas. 

Gals,  per  Min.  =  .0034  X  Diameter2  X  Stroke  in  ins.  X  No.  of 

Strokes. 
Sq.  of  Diam.  =  Gals,  per  Min.  -fr  (.0034  X  Stroke  in  ins.  X 

No.  of  Strokes). 

Square  of  Diameter  X  34 
Length  of  Stroke  =     Gals,  per  Min.  -  No.  of  Stroke8 

Square  of  Diameter  X  34 
No.  of  Strokes  =  Gals,  per  Min.  -        -  Length  of  Stroke 


HANDBOOK   ON   ENGINEERING. 


619 


CHAPTER      XXI. 
MECHANICAL  REFRIGERATION. 

About  the  first  thing  asked  by  persons  who  are  becoming 
interested  in  the  subject  of  refrigerating  and  ice-making  is,  "  Tell 
me  how  the  thing  is  done  ?  " 

Mechanical  refrigeration,  primarily,  is  produced  by  the  evapo- 
ration of  a  volatile  liquid  which  will  boil  at  low  temperature,  and 
by  means  of  a  special  apparatus  the  temperature  and  desired 
amount  of  refrigeration  is  placed  under  control  of  the  operator. 


Simplest  Apparatus 

Brine  Tank  or  Concealer  A. 


Fig.  298.    Elememtal  refrigerating  apparatus. 

The  simplest  form  of  refrigerating  mechanical  apparatus 
consists  of  three  principal  parts:  A,  an  u  evaporator,"  or,  as 
sometimes  called,  a  "  congealer,"  in  which  the  volatile  liquid  is 
vaporized;  -B,  a  combined  suction  and  compressor  pump,  which 


620 


HANDBOOK    ON    ENGINEERING. 


sucks,  or  properly  speaking,  "  aspirates  "  the  gas  discharged  by 
the  compressor  pumps,  and  under  the  combined  action  of  the 
pump  pressure  and  cold  condenser,  the  vapor  is  here  reconverted 
into  a  liquid,  to  be  again  used  with  congealer.  We  now  see  the 
function  of  the  compressor  pumps  and  condensers. 

PRINCIPLES  OF  OPERATION. 

The  action  of  all  refrigerating  machines  depends  upon  well- 
defined  natural  laws  that  govern  in  all  cases,  no  matter  what  type 
of  apparatus  or  machine  is  used,  the  principle  being  the  same  in 
all ;  while  processes  may  slightly  vary,  the  properties  of  the  par- 
ticular agent  and  manner  of  its  use  affecting,  of  course,  the 
efficiency  or  economic  results  obtained. 


Watef  Suppl/ 

j^CondenserO 


B         B         U         H         B          y  U          B 

— ^^^JSy  EXPANSIONS 

i        Brine  Tank  or  Congealer  A. 


Compression 

Refrigerating 

Apparatus 

Three  Parts 


Fig.  299.    Outline  drawing  of  mechanical  compression  system. 

OPERATION   OF   APPARATUS. 

I 

See  Fig*  299*  The  apparatus  being  charged  with  a  sufficient 
quantity  of  pure  ammonia  liquid,  which  we  will,  for  simplicity, 
assume  to  be  stored  in  the  lower  part  of  the  condenser  0,  a  small 
cock  or  expansion  valve  controlling  a  pipe  leading  to  the  congealer 


HANDBOOK    ON    ENGINEERING.  621 

or  brine  tank  A,  is  slightly  opened,  thus  allowing  the  liquid  to 
pass  in  the  same  office  as  a  tube  or  flue  in  steam  boiler  and  having 
precisely  the  same  function,  it  may  be  called  heating  or 
steam  making  service.  The  amount  of  water  capable  of  being 
boiled  into  steam  in  a  boiler  depends  upon  the  square  feet  of 
heating  surface,  temperature  of  fire  and  pressure  of  steam  ;  and 
the  same  is  true  of  the  capacity  of  heating  surface  pre- 
.  sented  by  the  coils  in  the  evaporator.  The  heat  is  transmitted 
through  the  coils  from  surrounding  substance  to  the  ammonia 
liquid,  which  is  boiled  into  a  vapor  the  same  as  water  is  boiled 
into  steam  in  a  steam  boiler ;  as  previously  explained,  the  heat 
thus  becomes  cooler ;  the  amount  taken  up  and  made  negative 
being  in  proportion  to  the  pounds  of  liquid  ammonia  evaporated. 

FUNCTION  OF  THE  PUMP  AND  CONDENSER. 

The  office  of  the  compressor,  pump  and  condenser  is  to  re- 
convert the  gas  after  evaporation  into  a  liquid,  and  make  the 
original  charge  of  ammonia  available  for  use  in  the  same  appa- 
ratus, over  and  over  again.  It  will  appear  to  the  reader,  after 
having  carefully  followed  the  text,  that  the  pump  and  condenser 
might  be  dispensed  with,  but  these  conditions  may  only  be  eco- 
nomically realized  when  the  at  present  expensive  ammonia 
liquid  can  be  obtained  in  great  quantities  and  at  less  cost  than 
the  process  of  reconverting  the  vapor  into  a  liquid  by  compression 
machinery  and  condenser  on  the  spot. 

WHAT  DOES  THE  WORK? 

The  real  index  of  the  amount  of  cooling  work  possible  is  the 
number  of  pounds  of  ammonia  evaporated  between  the  observed 
range  of  temperature.  To  make  the  above  clear,  we  will  add 
that  each  pound  of  ammonia  during  evaporation  is  capable  of 
Storing  up  a  certain  quantity  of  heat,  and  that  the  simplest  forms 


622  HANDBOOK    ON    ENGINEERING. 

of  refrigerating  apparatus  might  consist,  as  shown  by  engraving, 
of  two  parts,  to  wit :  A  congealer  and  a  tank  of  ammonia.  In  this 
apparatus  the  ammonia  is  allowed  to  escape  from  the  tank  into 
the  congealer  as  fast  as  the  coils  therein  are  capable  of  evapo- 
rating the  liquid  into  a  gas.  When  completely  evaporated  the 
resulting  vapor  is  allowed  to  escape  into  the  atmosphere,  which 
means  it  is  wasted,  the  supply  being  maintained  by  furnishing 
fresh  tanks  of  ammonia  as  fast  as  contents  are  exhausted.  This 
process,  while  simple,  would  be  tremendously  expensive,  costing 
at  the  rate  of  about  $200  per  ton,  refrigerating  or  ice-melting 
capacity.  To  recover  this  gas  and  reconvert  to  a  liquid  on  the 
spot  in  a  comparatively  inexpensive  manner,  is  the  object  to  be 
obtained. 

MECHANICAL  COLD  EASILY  REGULATED. 

This  being  under  the  control  of  the  cock  or  valve  leading  from 
the  condenser  called  an  expansion  valve.  As  the  gas  begins  to 
form  in  the  evaporator,  the  compressor  pump  B  is  set  in  motion 
at  such  a  speed  as  to  carry  away  the  gas  as  fast  as  formed,  which 
is  discharged  into  the  condenser  under  such  pressure  as  will  bring 
about  a  condensation  and  restore  the  gas  to  the  liquid  state  ;  the 
operation  being  continuous  so  long  as  the  machinery  is  kept  in 
motion. 

UTILIZING   THE   COLD. 

To  utilize  the  cold  thus  produced  for  refrigerating,  two  meth- 
ods are  in  use,  the  first  of  which  is  called  the  brine  system ;  the 
second  is  known  to  the  trade  as  the  direct  expansion  system,  both 
of  which  systems  will  be  explained  at  some  length. 

BRINE   SYSTEM. 

In  this  method,  the  ammonia  evaporating  coils  are  placed  in  a 
tank,  which  is  filled  with  strong  brine  made  of  salt,  which  is  well 
known  not  to  freeze  at  temperature  as  low  as  zero.  This  is  the  brine 


HANDBOOK.  ON    ENGINEERING.  623 

tank  or  congealer  A.  The  evaporating  or  expansion  of  the  ammo- 
nia in  these  coils  robs  the  brine  of  heat,  as  heretofore  explained, 
the  process  of  storing  cold  in  the  brine  going  on  continuously  and 
being  regulated,  as  required,  at  the  gas  expansion  valve.  To 
practically  apply  the  cold  thus  manufactured,  the  chilled  brine  or 
non-freezing  liquid  is  circulated  by  means  of  a  pump  through 
coils  of  pipe  which  are  placed  on  the  ceilings  or  sides  of  the  apart- 
ments to  be  refrigerated,  the  process  being  analogous  to  heating 
rooms  by  steam. 

THE   BRINE   COOLS  THE   ROOMS. 

The  cold  brine  in  its  circuit  along  the  pipes  becomes  warmer 
by  reason  of  taking  up  the  heat  of  the  rooms,  and  is  finally 
returned  to  the  brine  tank,  where  it  is  again  cooled  by  the  ammo- 
nia coils,  the  operation,  of  course,  being  a  continuous  one. 

DIRECT  EXPANSION  SYSTEM. 

By  this  method,  the  expansion  or  evaporating  coils  are  not  put 
in  brine  tanks,  but  are  placed  in  the  room  to  be  refrigerated,  and 
the  ammonia  is  evaporated  in  the  coils  by  coming  in  direct  con- 
tact with  the  air  in  the  room  to  be  refrigerated,  no  evaporating 
tank  being  used. 

RATING   OF  THE   MACHINE    IN  TONS   CAPACITY. 

For  the  information  of  the  unskilled  reader,  we  will  state  that 
machines  are  susceptible  of  two  ratings;  that  is,  either  their 
capacity  is  given  in  tons  of  ice  they  will  produce  in  one  day  (24 
hours),  called  ice-making  capacity  ;  or  they  are  rated  equal  to  the 
cooling  work  done  by  one  ton  of  ice-making  per  day  (24  hours), 
called  refrigerating  capacity. 

DIFFERENCE   IN   THESE   RATINGS 

Ordinarily  the  ice-making  capacity  is  taken  at  about  one-half 
of  the  refrigerating  capacity,  but  this  is  only  approximate, 


624  HANDBOOK    ON    ENOINKKR1NG. 

INSTRUCTIONS   FOR  OPERATING  REFRIGERATING  AND   ICE- 
MAKING  HACHINERY. 

First,  a  competent  engineer  should  be  placed  in  charge  of  the 
plant,  and  he  should  be  held  responsible  for  the  performance  of 
the  plant. 

He  should  have  charge  of  all  help  in  the  engine  room,  tank- 
room,  and  all  men  who  work  around  the  plant. 

He  should  acquaint  himself  with  all  pipe  and  valves  about 
the  plant,  so  that  in  case  of  trouble,  he  will  know  what 
to  do. 

Valves  should  be  provided  in  suitable  places,  so  that  if  it  be- 
comes necessary,  he  can  transfer  the  ammonia  from  one  part  of 
the  plant  to  another  ;  before  attempting  to  transfer  the  ammonia, 
the  engineer  in  charge  should  carefully  see  that  he  fully  under- 
stands where  the  ammonia  is  to  be  put,  and  that  there  is  suffi- 
cient space  to  contain  same.  In  making  transfers,  always  run 
the  machine  very  carefully. 

When  starting  the  engine,  start  slowly,  and  before  the  pumps 
show  a  vacuum  in  the  coils,  open  the  regulating  valve  slightly, 
and  then  speed  up  the  engine  gradually. 

The  back  pressure  should  be  kept  at  about  15  pounds  above 
zero,  depending  on  the  frost  shown  on  suction  pipe.  When  the 
machine  is  run  to  its  full  capacity,  it  should  show  frost  on 
the  suction  pipe  just  above  the  brine  tank ;  in  some  machines,  it 
is  necessary  to  freeze  back  to  machine,  as  the  frost  takes  up  the 
heat  of  compression  and  takes  the  place  of  the  water  jacket. 

In  general,  the  engineer  in  starting  the  machine,  will  first  see 
that  the  discharge  valves  are  open,  then  start  the  machine  slowly, 
and  open  the  suction  valves  slowly.  When  the  machine  is  fully 
up  to  speed,  watch  the  gauges  and  note  the  pressure.  The  con- 
denser pressure  should  be  somewhere  between  150  and  180  Ibs. 


HANDBOOK  -ON    ENGINEERING.  625 

depending  upon  the  temperature  of  the  water  and  atmosphere. 
The  suction  or  back  pressure  should  be  about  20  pounds,  unless  the 
temperature  of  the  brine  in  the  tanks  is  below  18  degrees  ;  if  it  is, 
the  low  pressure  should  be  reduced  in  proportion ;  the  frost  on 
the  suction  pipe  will  determine  the  back  pressure  to  be  carried. 
It  is  advisable  to  use  as  high  a  back  pressure  as  possible  without 
frosting  back. 

Regulate  the  low  pressure  by  means  of  the  feed  valves.  The 
pressure  should  rise  slowly  ;  watch  carefully  to  see  that  the  feed 
valves  work  regularly  so  that  each  valve  may  supply  the  proper 
amount  of  ammonia  to  the  coils . 

The  frosting  of  the  valves  will  indicate  how  they  are  working, 
and  a  little  practice  will  enable  the  engineer  to  judge  of  this. 

When  the  ammonia  disappears  from  the  liquid  receiver,  it  is 
possible  that  too  much  feed  has  been  given  the  coils,  and  that  they 
are  flooded ;  it  is  well  to  shut  off  the  main  liquid  valve  to  the 
tanks  and  pump  them  out  until  the  back  pressure  falls  to  about 
five  pounds ;  the  valve  can  then  be  opened  and  the  regular 
operation  resumed. 

This  pumping  down  is  for  the  purpose  of  getting  the  ammonia 
all  out  of  the  tank  coils,  where  it  will  sometimes  lie;  when  this  is 
the  case,  the  suction  line  to  the  machine  will  be  frosted,  even 
when  the  tanks  are  not  below  temperature  of  18  degrees ;  when 
the  tanks  are  below  18  degrees,  frost  will  generally  appear  in  the 
suction  line  to  the  machine. 

In  case  of  a  leak  in  the  pipe,  the  connections  are  made  to  the 
pumps  so  that  the  large  valves  on  the  suction  and  discharge  pipes 
may  be  closed,  and  the  small  by-pass  valves  opened  and  by 
running  the  machine  slowly,  the  discharge  pipe  system  can  be 
pumped  into  the  suction  and  brine  tanks.  In  case  of  a  leak 
in  the  suction  side,  it  is  only  necessary  to  shut  off  the  liquid 
valve  and  pump  all  of  the  ammonia  up  into  the  condenser  and  keep 
it  there  by  shutting  the  valve. 

When  shutting  down  a  machine,  close  the  liquid  valve  on  the 


626  HANDBOOK    ON    ENGINEERING. 

brine  tank,  and  run  the  machine  until  the  pressure  is  brought 
down  to  zero  on  the  gauge.  Do  not  create  a  vacuum,  because 
air  is  liable  to  leak  into  the  pumps  through  the  stuffing 
boxes. 

It  is  well  to  watch  the  compressor  carefully  for  leaks ;  a 
leak  into  the  cylinder  either  through  leaky  discharge  valves, 
the  gaskets  or  the  cylinder  head  gasket  between  the  cylinder 
and  the  discharge  port,  will  materially  reduce  the  compressor 
capacity.  It  will  not  take  long  for  a  compressor  to  waste  a  ton 
of  coal. 

If  the  engineer  in  charge  of  a  compressor  has  a  chance,  he 
should  take  off  the  cylinder  head  and  examine  the  cylinder 
gasket.  If  it  looks  bad,  replace  it  with  a  new  one;  rub  the 
valves  to  their  seats  with  flour  of  emery  and  oil,  and  see  that  they 
have  a  good  bearing ;  also  examine  the  valve  cage  gaskets. 

A  good  test  for  a  compressor,  to  see  whether  all  connections 
are  tight  about  the  compressor,  is  to  connect  a  pressure  gauge  to 
the  indicator  connection ;  compress  the  gas  in  the  cylinder 
so  as  to  have  a  high  pressure.  Note  the  pressure  on  the  gauge. 
If  it  does  not  decrease,  the  compressor  and  connections  are 
tight.  .  If  it  decreases  rapidly,  either  the  valves  need  regrinding, 
or  the  piston  needs  new  rings,  or  the  cylinder  should  be  rebored, 
or  all  these  troubles  may  exist  at  the  same  time. 

All  pipe  and  fittings  between  the  machine  and  condenser, 
should  be  looked  after  as  all  flanges  are  provided  with  lead 
gaskets,  and  these  flanges  should  be  examined  occasionally,  and 
when  the  plant  is  shut  down  and  allowed  to  cool,  the  flanges 
should  be  tightened  up. 

The  pipes  of  the  condensers  should  be  kept  as  clean  as 
possible,  so  that  the  water  will  flow  evenly  over  all  pipes  alike, 
in  order  to  extract  as  much  heat  as  possible  from  the  ammonia. 

The   colder  the  ammonia  can  be  kept   in  the  condenser,  the 


HANDBOOK   ON   ENGINEERING.  627 

more  work  it  will  do  in  the  tanks ;  on  this  account,  well  water  18 
to  be  preferred. 

The  oil  trap  on  the  line  from  the  machine  to  the  condenser, 
should  be  examined  once  every  ten  days  and  the  oil  drawn  off. 

If  the  system  gets  clogged  with  oil,  and  where  there  is  more  than 
one  tank,  pump  the  brine  into  the  other  tanks  and  when  the  brine 
is  all  out  of  the  tank,  disconnect  the  coil  at  top  and  bottom,  con- 
nect steam,  attach  a  gauge,  and  then  drive  a  pine  plug  in  bottom 
of  coil  and  put  about  30  pounds  of  steam  on  coil  for  ten  or 
twenty  minutes  ;  on  the  bottom  of  the  return  header  is  a  purge 
cock  that  must  be  opened  frequently,  while  the  steam  is  on 
coil.  Then  knock  plug  out  of  coil  at  bottom,  and  let  the  steam 
come  through  coil  for  a  short  time,  and  then  disconnect  the  steam 
and  connect  the  air  pump  to  the  coil  and  put  on  thirty  pounds 
air  pressure  for  ten  minutes ;  all  coils  must  be  treated  in  the 
same  way. 

If  there  is  only  one  tank,  the  coils  must  be  taken  out  of  tank 
and  blown  out,  or  the  brine  pumped  into  the  cans.  At  the 
same  time,  the  expansion  valves  must  be  overhauled.  After  all 
coils  and  headers  are  connected  the  whole  should  be  tested  for 
leaks,  first,  under  air  pressure,  and  second,  with  ammonia  and  a 
sulphur  stick  while  the  tank  is  empty. 

The  sulphur  sticks  are  prepared  by  dipping  a  stick  of  wood 
into  melted  sulphur.  The  sticks  are  then  burned  close  to  where 
leaks  are  suspected.  Any  leak  is  at  once  indicated  by  a  white 

smoke. 
• 

STEAH    CONDENSERS. 

Steam  and  ammonia  condensers  should  be  kept  clean  and  free 
from  all  scale,  and  should  be  supplied  with  sufficient  water  to 
condense  the  steam  and  ammonia. 


628  HANDBOOK    ON    ENGINEERING. 

THE   REBOILERS. 

The  reboilers  are  for  the  purpose  of  removing  any  air  or 
gases  which  may  be  in  the  steam.  The  water  in  the  reboilers 
should  at  all  times  be  kept  boiling,  for  if  it  is  not,  the  ice  will  be 
white.  The  regulating  valves  on  the  reboilers  should  be  exam- 
ined often,  to  see  that  they  are  not  sticking.  A  steam  connection 
should  be  provided  in  the  flat  coolers,  so  that  after  shutting  off 
the  water,  which  flows  over  the  cooler,  and  the  water  from  the 
reboilers,  steam  may  be  blown  through  it  from  the  top  downward 
and  out  at  the  bottom  of  the  coil ;  this  should  be  done  frequently, 
land  it  will  be  found  to  save  the  filters. 

The  oil  separator  should  be  examined  at  least  once  a  year  and 
cleaned.  The  object  of  this  separator  is  to  remove  the  oil  from 
the  steam,  and,  if  working  properly,  there  should  be  a  small 
stream  of  water  and  oil  flowing  from  the  drain. 

AIR   IN   THE   SYSTEM. 

When  air  or  permanent  gases  are  in  the  system,  it  will  be 
manifested  by  unusually  high  condenser  pressure,  and  the  effi- 
ciency of  the  machine  will  be  reduced.  To  remove  the  air,  attach 
a  bent  piece  of  one-fourth  inch  pipe  to  the  small  valve  placed  on  the 
top  of  the  condenser  ;  place  the  other  end  of  the  pipe  in  a  bucket 
of  water ;  open  the  valve  slightly,  and  if  air  is  present,  it  will 
bubble  up  through  the  water,  while  the  ammonia  will  produce  a 
crackling  noise,  the  same  as  when  steam  is  turned  into  water, 

GASES   IN  THE   PLANT. 

Accumulation  of  gases  in  a  plant  sometimes  consists  of  atmos- 
pheric air,  but  sometimes  also  of  hydrogen  and  nitrogen,  due  to 
the  decomposition  of  ammonia. 


HANDBOOK  -ON    ENGINEERING.  629 

The  best  way  to  remove  these  gases  from  the  system,  is  by 
drawing  them  off  at  the  top  of  the  ammonia  condenser  coils, 
where  a  small  valve  will  be  found  on  top  of  each  coil  where  a 
small  pipe  may  be  attached  to  the  small  valves  ;  put  the  other  end  in 
a  bucket  of  water.  If,  on  opening  the  valve,  bubbles  are  seen  to 
escape  through  the  water,  the  valve  should  be  kept  open  as  long 
as  such  bubbles  appear ;  when  a  crackling  noise  is  heard  in  the 
water,  close  the  valve. 

Every  engineer  should  keep  himself  posted  as  to  the  exact 
clearance  existing  between  the  piston  and  the  head  or  heads  of 
the  compressor.  A  convenient  way  to  ascertain  this,  is  to 
remove  one  of  the  valves  from  the  compressor  head  and  insert  a 
piece  of  soft  lead  rolled  in  the  shape  of  a  wire  through  the  valve 
chamber  into  the  cylinder  and  pinch  the  machine  over  until  the 
piston  of  the  compressor  squeezes  the  lead  against  the  head. 
When  the  lead  is  withdrawn,  the  exact  clearance  will  be  shown. 

If  the  valves  pound,  it  may  be  that  the  valves  have  too  much 
lift.  Try  a  stiffer  spring.  A  spring  that  is  too  stiff  will  also 
cause  valves  to  pound. 

Never  create  a  vacuum  in  an  ammonia  system,  unless  it  is 
absolutely  necessary  to  repair  a  leak  or  for  similar  purposes ;  it 
will  have  a  tendency  to  admit  air  into  the  system  ;  the  air  must  be 
kept  out ;  pump  to  zero  on  the  gauge,  but  no  lower. 

Never  put  any  ammonia  in  a  plant  until  it  has  been  tested ; 
this  can  be  done  by  drawing  a  sample  out  of  the  drum  and  seeing 
that  it  will  all  evaporate  and  leave  no  residue. 

Keep  a  record  of  the  temperatures  of  brine  and  condensing 
water,  and  evaporating  and  condensing  pressures. 

It  is  a  good  plan  to  have  a  duplicate  set  of  valves  on  hand,  all 
ready  to  replace  any  leaky  valve. 

A  leaky  suction  valve  is  sometimes  the  cause  of  considerable 
loss  in  capacity.  It  can  be  located  by  heat  on  the  suction  con- 
nection or  by  the  hiss  that  is  ever  present  when  a  valve  leaks, 
or  by  the  appearance  of  the  valve. 


630  HANDBOOK    ON    ENGINEERING. 

Test  the  oil  that  is  being  used  in  the  compressors  by  subject- 
ing a  sample  to  low  temperature  —  get  a  bottle  of  the  oil  and 
cover  with  fine  ice  and  salt ;  the  result  will  demonstrate  whether 
it  will  stand  a  low  temperature  or  not.  If  the  oil  gets  thick  and 
gummy,  and  a  separation  occurs,  leaving  a  thin  transparent, 
watery  liquid,  in  which  the  heavy  part  of  the  oil  settles,  and 
which  gives  off  an  odor  like  benzine.  Reject  the  oil,  as  it  will 
produce  gases  in  the  system,  and  give  trouble. 

Oil  may  be  tested  with  ammonia  gas ;  animal  fat  will  saponify 
when  subjected  to  alkali  tests. 

In  ice  plants,  the  engineer  should  see  that  the  ice  is  always 
pulled  regularly.  The  distilled  water  is  supplied  regularly  and 
it  should  be  used  in  the  same  way ;  pull  but  one  can  and  refill 
before  pulling  the  next. 

Keep  the  brine  in  the  tanks  over  the  top  pipe ;  at  the  end  of 
the  season,  when  the  plant  is  shut  down,  leave  the  cans  in  the 
brine  for  if  the  cans  are  taken  out,  the  brine  will  be  lowered  and 
where  the  pipes  are  exposed,  they  will  rust  very  fast ;  keep  the 
tank  covers  clean.  The  strength  of  the  brine  should  be  about  80 
on  a  saltometer. 

If  ice  forms  on  the  coils,  the  brine  is  weak,  and  the  brine  must 
be  strong  enough  so  it  will  not  freeze. 

In  making  repairs  to  coils,  while  immersed  in  brine  the  work- 
men should  besmear  their  arms  and  hands  with  cylinder  oil,  or 
lard  or  tallow,  as  that  will  enable  them  to  keep  them  in  the  brine 
longer. 

In  case  the  temperature  of  the  brine  rises  above  30  de- 
grees, do  not  attempt  to  reduce  the  temperature  without  first 
examining  the  cans  to  see  whether  the  ice  has  thawed  loose  from 
them;  in  case  it  has  thawed,  pull  all  ice  and  refill  the  cans 
before  reducing  temperature  ;  if  this  is  not  done,  the  freezing  of 
the  water  around  the  ice  in  the  cans  will  burst  them. 


HANDBOOK    ON    ENGINEERING.  631 

TESTING  FOR  WATER  BY  EVAPORATION. 

As  shown  by  the  engraving,  screw  into  the  ammonia  flask  a 
piece  of  bent  one-quarter  inch  pipe,  which  will  allow  a  small  bot- 
tle to  be  placed  so  as  to  receive  the  discharge  irom  it.  This  test 
bottle  should  be  of  thin  glass  with  wide  neck,  so  that  quarter-inch 
pipe  can  pass  readily  into  it,  and  of  about  12  cubic  inches  capac- 
ity. Put  the  wrench  on  the  valve  and  tap  it  gently  with  a  ham- 
mer. Fill  the  bottle  about  one-third  full  and  throw  sample  out 
in  order  to  purge  valve,  pipe  and  bottle.  Quickly  wipe  off  mois- 
ture that  has  accumulated  on  the  pipe,  replace  the  bottle  and  open 


Fig.  300.    Showing  connections  to  flask. 

valve  gently,  filling  the  bottle  about  half  full.  This  last  operation 
should  not  occupy  more  than  one  minute.  Remove  the  bottle  at 
once  and  insert  in  its  neck  a  stopper  with  a  vent  hole  for  the 
escape  of  the  gas.  A  rubber  stopper  with  a  glass  tube  in  it  is 
the  best,  but  a  rough  wooden  stopper,  loosely  put  in,  will  answer 
the  purpose.  Procure  a  piece  of  solid  iron  that  should  weigh  not 
less  than  eight  or  ten  pounds,  pour  a  little  water  on  this  and  place 
the  bottle  on  the  wet  place.  The  ammonia  will  at  once  begin  to 
boil,  and  in  warm  weather  will  soon  evaporate.  If  any  residuum, 
pour  it  out  gently,  counting  the  drops  carefully.  Eighteen  drops 
are  about  equal  to  one-tenth  of  an  ounce,  and  if  the  sample  taken 


632 


HANDBOOK    OX    ENGINEERING. 


amounts  to,  say,  6  cubic  inches,  we  can  readily  approximate  the 
percentage  of  the  liquid  remaining. 


Fig.  301.    Sectional  view  of  10-ton  refrigerating  machine. 


LUBRICATION   OF   REFRIGERATING   MACHINERY. 

It  is  well  to  speak  of  this,  for  the  reason  that  it  is  an  important 
subject ;  and  some  users  of  machinery  think  that  a  cheap,  low 


HANDBOOK    ON    ENGINEERING.  633 

grade  of  oil  is  really  the  cheapest.  To  disabuse  their  minds  of 
this  idea  and  suggest  the  necessity  of  high  grade  oils,  both  on  the 
score  of  economy  and  to  keep  the  machinery  at  all  times  in 
efficient  running  order,  we  suggest  the  following:  First-class 
refrigerating  machinery  calls  for  the  use  of  at  least  three  different 
kinds  of  oil,  Nos.  1,  2  and  3,  each  of  high  grade :  — 

No*  J*  For  use  in  the  steam  cylinder,  and  is  known  in  the  trade 
as  cylinder  oil.  This  ranges  in  price  from  50c,  to  $1  per  gallon. 
Good  cylinder  oil  should  be  free  from  grit,  not  gum  up  the  valves 
and  cylinder,  should  not  evaporate  quickly  on  being  subjected  to 
heat  of  the  steam,  and  when  cylinder  head  is  removed,  a  good 
test  is  to  notice  the  appearance  of  the  wearing  surfaces ;  they 
should  be  well  coated  with  lubricant  which,  upon  application  of 
clean  waste,  will  not  show  a  gummy  deposit  or  blacken.  Use  this 
oil  in  a  sight  feed  lubricator  with  regular  feed,  drop  by  drop. 

No*  2*  For  use  of  all  bearing  and  wearing  surfaces  of  machine 
proper  —  an  oil  that  will  not  gum,  not  too  limpid,  with  good 
body,  free  from  grit  or  acid  and  of  good  wearing  quality,  flowing 
freely  from  the  oil  cups  at  a  fine  adjustment  without  clogging, 
and  a  heavier  grade  should  be  used  for  lubricating  the  larger 
bearings. 

No*  3*  For  use  in  compressor  pumps.  This  oil  should  be  what 
is  called  a  cold  test,  or  zero  oil,  of  best  quality. 

Best  paraffine  oil  is  sometimes  used ;  as  also  a  clear  West  Vir- 
ginia crude  oil.  This  oil,  when  subjected  to  a  low  temperature, 
should  not  freeze. 

EFFECTS  OF  AMMONIA  ON  PIPES. 

Ammonia  has  no  chemical  effect  upon  iron ;  a  tank,  pipe  or 
stop-cock  may  be  in  constant  contact  with  ammonia  for  an  in- 
definite time  and  no  action  will  be  apparent.  The  only  protec- 
tion, therefore,  that  ammonia-expanding  pipes  require  is  from 
corrosion  on  the  outer  surface.  As  long  as  the  pipes  are  covered 


634  HANDBOOK    ON    ENGINEERING. 

with  snow  or  ice,  corrosion  does  not  occur ;  the  coating  of  ice 
thoroughly  protects  them  from  the  oxidizing  effect  of  the  atmos- 
phere ;  but  alternate  freezing  and  thawing  requires  protected  sur- 
faces, which  are  best  obtained  by  applying  a  coat  of  paint  every 
season. 

Expansion  coils  having  to  withstand  but  a  maximum  working 
pressure  of  thirty  pounds  per  square  inch,  are  constructed  with 
such  absolute  security,  in  whole  and  in  detail,  as  to  make  them 
one  of  the  most  perfect  pipe  constructions  on  a  large  scale  ever 
applied  in  practice. 


Fig.  302.    Position  of  tank  to  be  emptied. 

TO  CHARGE  THE  SYSTEM  WITH  AMMONIA. 

Position  of  the  tank  should  be  as  shown,  the  outlet  valve 
pointing  upwards  and  the  other  end  of  the  tank  raised  12"  to  15". 
The  connection  between  the  outlet  valve  of  the  tank  and  the 
inlet  cock  of  the  system  should  be  a  |"  pipe.  In  charging,  open 
valve  of  the  tank  cautiously  to  test  connection  ;  if  this  is  tight, 
open  valve  fully ;  start  machine  and  run  slowly  till  tank  is  empty. 
The  tank  is  nearly  empty  when  frost  begins  to  appear  on  it ;  run 
the  machine  till  suction  gauge  reaches  atmospheric  pressure.  If 
it  holds  at  this  pressure  when  machine  is  stopped,  the  tank  is 
empty  ;  if  not,  start  up  again.  In  disconnecting,  close  the  valve 
on  the  tank  first,  the  inlet  cock  of  the  system.  Weigh  tank 


HANDBOOK    (ON    ENGINEERING.  635 

before  and  after  emptying ;  each  standard  tank  contains  from  100 
to  110  pounds  of  ammonia. 

PROCESS  OF  MECHANICAL  REFRIGERATION. 

The  process  of  mechanical  refrigeration  is  simply  that  of 
removing  heat,  and  mechanism  is  necessary,  because  the  rooms 
and  articles  from  which  the  heat  is  to  be  removed  are  already  as 
cold,  or  colder  than  their  surroundings,  and  consequently,  the 
natural  tendency  is  for  the  heat  to  flow  into  them  instead  of  out  of 
them.  The  fact  that  a  body  is  already  cold  does  not  prevent  the 
removal  of  more  heat  from  it  and  making  it  still  colder.  The  term 
cold  describes  a  sensation  and  not  a  physical  property  of  matter ; 
the  coldest  bodies  we  commonly  meet  with  are  still  possessed  of  a 
large  quantity  of  heat,  part  of  which,  at  least,  can  be  abstracted 
by  suitable  means.  The  only  means  by  which  heat  can  be 
removed  from  a  body  is  to  bring  in  contact  with  it  a  body  colder 
than  itself.  This  is  the  function  that  ammonia  performs  in 
mechanical  refrigeration.  It  is  so  manipulated  as  to  become 
colder  than  the  body  we  wish  to  cool.  The  heat  thus  abstracted 
by  it  is  got  rid  of  by  such  further  manipulation  that  (while  still 
retaining  the  heat  it  has  absorbed)  it  will  be  hotter  than  ordi- 
nary cold  water,  and  therefore,  part  with  its  heat  to  it.  Ammonia 
thus  acts  like  a  sponge.  It  sops  up  the  heat  in  one  place  and 
parts  with  it  in  another,  the  same  ammonia  constantly  going 
backward  and  forward  to  fetch  and  discharge  more  heat.  The 
complete  cycle  of  operation  comprises  three  parts :  — 

1st.  A  compression  side,  in  which  the  gas  is  compressed. 

2d.  A  condensing  side,  generally  consisting  of  coils  of  pipe, 
in  which  the  compressed  gas  circulates,  parts  with  its  heat  and 
liquefies. 

3d.  An  expansion  side,  consisting  also  of  coils  of  pipe, 
in  which  the  liquefied  gas  re-expands  into  a  gas,  absorbs  heat, 
and  performs  the  refrigerating  work. 


()36  HANDBOOK    ON    ENGINEERING. 

In  order  to  render  the  operating  continuous,  these  three  sides 
or  parts  are  connected  together,  the  gas  passing  through  them  in 
the  order  named.  The  liquefied  gas  is  allowed  to  flow  into  the 
expansion  or  evaporating  coils,  where  it  vaporizes  and  expands 
under  a  pressure  varying  from  10  to  30  pounds  above  that  of  the 
atmosphere,  when  ammonia  is  the  agent  in  use.  The  gas  then 
passes  into  the  compressor,  is  compressed  and  forced  into  the 
condensers,  where  a  pressure  from  125  to  175  pounds  per  square 
inch  usually  exists ;  here  liquefaction  takes  place  and  the  re- 
sulting liquefied  gas  is  allowed  to  flow  to  a  stop-cock  having  a 
minute  opening,  which  separates  the  compression  from  the  expan- 
sion side  of  the  plant.  The  expansion  side  consists  of  coils  of 
pipe  similar  to  those  of  the  condensing  side,  but  used  for  the 
reverse  operation,  which  is  the  absorption  of  heat  by  the  vapor- 
ization of  liquefied  gas  instead  of  the  expulsion  of  heat  from  it, 
as  in  the  former  operation.  Heat  is  conducted  through  the  ex- 
pansion or  cooling  coils  to,  and  is  absorbed  by,  the  vaporizing 
and  expanding  liquefied  gas  within  such  coils,  for  the  reason  that 
they  are  connected  to  the  suction  or  low  pressure  side  of  the 
apparatus  from  which  the  compressors  are  continually  drawing 
the  gas  and  thereby  reducing  the  pressure  in  said  coils,  as  already 
stated,  to  a  pressure  of  10  to  30  pounds  above  the  atmosphere; 
it  being  kept  in  mind  that  liquefied  ammonia  in  again  assuming 
a  gaseous  condition,  has  the  power  or  capacity  of  reabsorbing, 
upon  its  expansion,  a  large  quantity  of  heat.  The  liquefied  gas 
entering  these  coils  through  the  minute  openings  of  the  stop-cock, 
above  referred  to,  is  relieved  of  a  pressure  of  125  to  175  pounds, 
the  amount  requisite  to  maintain  it  in  a  liquid  condition,  when  it 
begins  to  boil,  and  in  so  doing  passes  into  the  gaseous  state.  To 
do  this  it  must  have  heat,  which  can  be  supplied  only  from  the 
substance  surrounding  the  pipes,  such  as  air,  brine,  wort,  etc. 
As  a  natural  result  the  surrounding  substances  are  reduced  in 
temperature,  or  cooled. 


HANDBOOK   ON   ENGINEERING. 


637 


PURGING  VALVE 


IDICATOR  VALVE 


Sectional  yiew  of  « Eclipse"  Compressor. 


638 


HANDBOOK    ON    ENGINEERING. 


304.    Section  of  De  La  Vergne  Donble-Acting  Vertical  Ammonia 
Compressor. 


HANDBOOK    ON    ENGINEERING. 


639 


640 


HANDBOOK  ON  ENGINEERING. 


THE  DE  LA  VERQNE  SYSTEM. 

The  diagram  on  page  640  is  seen  to  be  extremely  simple  in 
conception.  Ammonia  gas  is  received  by  the  compressor  ^ 
from  which  it  is  discharged  into  the  pressure  tank  B.  The  gas 
continues  into  the  condenser,  where  it  is  liquified  and  collects  in 
the  liquid  storage  tank  D.  The  liquid  ammonia  is  taken  off  from 
the  bottom  of  the  second  tank  and  passes  through  the  expansion 
cock  E  into  the  expansion  or  refrigerating  coil,  where  it  boils 
into  vapor.  This  is  drawn  off  into  the  compressor  to  pass  around 
again  in  the  order  above  described.  Before  entering  the  com- 
pressor the  gas  passes  through  the  scale  separator  or  trap  shown 
near  the  gauge  plate  where  any  scale  or  foreign  matter  is  re- 
moved from  the  ammonia. 


Fig.  306.    A  Diagram  of  the  De  La  Vergne  System. 


HANDBOOK    ON    ENGINEERING. 


64! 


642  HANDBOOK    ON    ENGINEERING. 

On  page  641  is  shown  in  diagram  the  general  arrangement  of 
a  standard  De  La  Vergne  Refrigerating  System  with  horizontal 
machine.  The  hot  gas  discharged  by  the  compressor  passes 
first  to  the  pressure  tank  from  whence  it  passes  up  the  riser 
marked  hot  gas  line,  through  a  check  valve  and  down  a  header 
through  two  inch  pipes  and  soft  seated  globe  valves  of  the  same 
size  to  the  individual  stands  of  atmospheric  condensers  at  the  bot- 
tom, and  as  the  liquid  forms,  it  is  drawn  off  at  different  levels 
through  the  several  small  pipes  shown  in  the  illustration,  and 
passes  into  the  liquid  header  from  where  it  goes  to  the  liquid 
tank.  The  outlet  from  the  liquid  header  rises  a  few  inches  to  form 
a  gooseneck,  which  maintains  a  liquid  seal  on  the  condenser  and 
prevent  gas  from  the  pressure  tank  from  getting  into  the  liquid 
line  leading  to  the  expansion  coils.  The  liquid  line  from  the  con- 
denser is  provided,  just  before  it  reaches  the  liquid  tank,  with  a 
pocket  into  which  any  scale  or  foreign  matter  is  precipitated. 

DE  LA  VERGNE  CAN  ICE  MAKING  PLANT. 

In  the  distilling  apparatus  for  can  ice  plants,  illustrated  on 
page  643 ,  the  exhaust  steam  from  the  engine  which  drives  the 
compressor  is  passed  first  through  a  grease  separator  A,  in  which 
the  exhaust  steam  impinging  on  the  water  in  the  bottom  of  the 
shell  and  the  baffle  plate  between  the  inlet  and  the  outlet,  pre- 
cipitates and  entrained  oil.  From  the  grease  separator  the  steam 
passes  the  usual  boiler  feed  water  heater  J5,  and  is  finally  con- 
densed in  the  surface  steam  condenser  (7,  the  condensation  from 
which  together  with  that  from  the  feed  water  heater  passes  to  the 
combined  skimmer  and  reboiler  D. 

In  the  reboiler  the  ebullition  is  effected  in  a  central  tank,  con 
centric  to  which  is  a  second  or  outer  tank,  the  space  between  the 
two  being  utilized  as  a  skimming   tank.     The   overflowing   wate 
in  the  jacket  of  the  skimming    tank   prevents   radiation   of  hea 
from  the  reboiling  tank  proper,  and  there  being  no   ebullition   in 


HANDBOOK    ON    ENGINEERING. 


643 


644  HANDBOOK    ON    ENGINEERING. 

this  outer  tank  to  disturb  the  surface  of  the  water,  skimming  is 
effected  with  a  minimum  loss  of  sweet  water. 

From  the  reboiler  the  water  passes  to  the  hot  water  storage 
tank,  E. 

In  order  to  keep  the  remaining  parts  of  the  distilled  water  sys- 
tem filled  at  all  times  and  thereby  prevent  any  re-absorption  of 
air  which  might  otherwise  take  place,  a  regulating  mechanism  is 
employed  which  in  case  of  low  water  in  the  hot  water  storage 
tank,  closes  the  valve  through  which  the  water  passes  into  the 
hose  of  the  can  filler. 

Ordinarily  the  hot,  reboiled,  distilled  water  from  tank  E,  passes 
through  the  condensed  water  cooling  coil  F,  over  which  is 
showered  cold  water  from  the  main  supply  line.  The  hot  dis- 
tilled water  enters  this  cooler  from  below,  and  leaving  the  top  of 
the  water-cooling  coil,  it  then  again  passes  downward  and  through 
the  deodorizer  H.  This  device  consists  of  a  cylindrical  shell  of  am- 
ple dimensions  filled  with  charcoal.  The  water  is  introduced 
through  a  strainer  under  a  false  bottom  so  perforated  as  to  give 
the  upward  flow  of  water  an  even  distribution  over  the  entire 
cross  section  of  the  filter  bed.  At  the  top  the  water  passes  a 
second  strainer  from  which  it  flows  to  the  can  filler. 

The  liquid  ammonia  leaves  the  liquid  tank  at  the  bottom 
through  the  main  liquid  line,  a  branch  from  which  after  passing 
through  a  strainer  is  connected  with  the  main  suction  line  just 
above  the  compressor  cylinder,  and  supplies  liquid  for  regulating 
compressor  temperatures  while  starting  up,  pumping  out,  etc. 

Just  outside  the  main  liquid  valve  a  small  connection  is  made 
into  the  main  liquid  line  to  which  ammonia  drums  may  be  con- 
nected for  charging  the  system.  Beyond  this  connection  the 
main  line  passes  to  the  cold  storage  rooms  and  branches  out  to 
the  individual  expansion  valves  on  the  various  cooling  coils. 

The  ammonia  gas  returning  from  each  coil  passes  through  a 
two  inch  soft  metal  seated  globe  valve,  which  together  with  the 


HANDBOOK    ON    ENGINEERING. 


645 


0, 

o 


be 

£ 


646 


HANDBOOK    ON    ENGINEERING. 


expansion  valve  allows  the  individual  coils  to  be  pumped  out, 
shut  off  and  disconnected. 

The  main  suction  line  is  provided  with  a  scale  separator  or 
trap  which  prevents  any  scale  or  other  foreign  substances  from 
entering  and  damaging  the  compressor  and  valves. 

The  compressor  is  lubricated  by  means  of  a  small  oil  pump 
shown  attached  to  the  right  hand  side  of  the  machine.  The  oil 
from  this  pump  is  forced  through  a  three-way  cock,  through  the 


Fig.  310*    Twin  cylinder  compressor,  witn 


steam  cylinders 


piston  rod  stuffing  box  lantern  and  into  the  oil  pot  situated 
just  above  the  stuffing  box.  The  second  line  leading  from  the 
three-way  cock  connects  with  the  pressure  tank  and  through  this 
line  the  oil  carried  over  with  the  ammonia  gas  may  be  blown  back 
through  a  strainer  into  the  lubricating  system. 

The  system  is  arranged  with  by-passes  so  that  the  ammonia 
from  any  part  of  the  whole  of  the  high  pressure  side  can  be 
pumped  out  and  discharged  into  the  low  pressure  side. 


HANDBOOK    ON    ENGINEERING.  647 

Through  the  connection  between  the  suction  and  equalizing  lines 
(shown  just  above  the  gauge  board  in  the  cut),  any  one  stand  of 
the  condensers  can  be  pumped  out  singly. 

Both  the  liquid  and  pressure  tanks  are  provided  with  gauge 
glasses  so  that  the  height  of  tlie  oil  or  liquid  ammonia  can  be 
readily  observed  at  any  time. 

The  condensers  are  provided  with  a  purging  and  equalizing 
header  running  the  entire  width  of  the  battery  of  condensers  con- 
nected with  each  stand  through  a  half-inch  soft  metal  seated 
valve.  The  impure  gases  collecting  at  the  top  of  the  condensers 
may  be  purged  from  the  header  through  the  blow-off  valve. 

Any  ammonia  gas  entering  the  oil  pot  from  the  stuffing  box 
lanterns  or  from  the  oil  blown  back  from  the  back  pressure  tank 
passes  up  through  the  equalizer  from  the  oil  pot  and  enters  the 
main  suction  from  the  top.  A  continuation  of  this  furnishes  the 
low  pressure  gauge  connection,  while  the  high  pressure  gauge  is 
connected  to  the  pressure  tank. 


648  HANDBOOK    ON    ENGINEERING. 


CHAPTER     XXII. 

SOflE    PRACTICAL    QUESTIONS    USUALLY    ASKED    OF    EN- 
GINEERS WHEN  APPLYING   FOR  LICENSE. 

Q.  If  you  were  called  on  to  take  charge  of  a  plant,  what  would 
be  your  first  duty?  A.  To  ascertain  the  exact  condition  of  the 
boiler  and  all  its  attachments  (safety-valve,  steam-gauge,  pump, 
injector)  and  engine. 

Q.  How  often  would  you  blow  off  and  clean  your  boilers  if 
you  had  ordinary  water  to  use?  A.  Twice  a  month. 

Q.  What  steam  pressure  will  be  allowed  on  a  boiler  50"  diam- 
eter, f"  thick,  60,000  T.  S.  £  of  tensile  strength  factor  of  safety? 
A.  One-sixth  of  tensile  strength  of  plate,  multiplied  by  thick- 
ness of  plate,  divided  by  one-half  of  the  diameter  of  boiler,  gives 
safe  working  pressure. 

Q.  How  much  heating  surface  is  allowed  per  horse-power  by 
builders  of  boilers  ?  A.  12  to  15  feet  for  tubular  and  flue  boilers. 

Q.  How  do  you  estimate  the  strength  of  a  boiler?  A.  By  its 
diameter  and  thickness  of  metal. 

Q.  Which  is  the  best,  single  or  double  riveting?  A.  Double 
riveting  is  from  16  to  20  per  cent  stronger  than  single. 

Q.  How  much  grate  surface  do  boiler-makers  allow  per  horse- 
power? A.  About  f  of  a  square  foot. 

Q.  Of  what  use  is  a  mud  drum  on  a  boiler,  if  any?  A.  For 
collecting  all  the  sediment  of  a  boiler. 

Q.  How  often  should  it  be  blown  out?  A.  Three  or  four  times 
a  day,  in  the  morning  before  starting,  and  at  noon. 

Q.  Of  what  use  is  a  steam  dome  on  a  boiler?  A.  For  storage 
of  dry  steam. 


HANDBOOK   ON    ENGINEERING.  649 

Q.  What  would  you  do  if  you  should  find  your  water  gone 
from  sight  very  suddenly?  A.  If  a  light  fire  draw  and  cool  off 
as  quickly  as  possible  ;  if  a  heavy  fire  cover  with  wet  ashes  or 
slack  coal.  Never  open  or  close  any  outlets  of  steam  when  your 
water  is  out  of  sight. 

Q.  What  precautions  should  you  take  to  blow  down  a  part  of 
the  water  in  your  boiler  while  running  with  a  good  fire?  A. 
Never  leave  the  blow-off  valve,  and  watch  the  water  level. 

Q,  How  much  water  would  you  blow  off  at  once  while  running  ? 
A.  Never  blow  off  more  than  one  gauge  of  water  at  a  time  while 
running. 

Q.  What  precautions  should  the  engineer  take  when  necessary 
to  stop  with  heavy  fires?  A.  Close  dampers,  put  on  injector 
or  pump,  and  if  a  bleeder  is  attached,  use  it. 

Q.  What  is  an  engineer's  first  duty  on  entering  a  boiler-room? 
A.  To  ascertain  the  true  water  level,  and  look  at  steam  gauge. 

Q.  When  should  a  boiler  be  blown  out?  A.  After  it  is  cooled 
off  —  never  while  it  is  hot. 

Q.  When  laying  up  a  boiler  what  should  be  done?  A.  Clean 
thoroughly  inside  and  out ;  remove  all  ' 4  Rust ' '  and  paint  rust 
places  with  red  lead ;  examine  all  stays  and  braces  to  see  if  any 
are  loose  or  badly  worn. 

Q.  Of  what  use  is  the  indicator?  A.  The  indicator  is  used  to 
determine  the  power  developed  by  an  engine,  to  serve  as  a  guide 
in  setting  valves  and  showing  the  action  of  steam  in  the  cylinder. 

Q.  How  would  you  increase  the  power  of  an  engine?  A.  To 
increase  the  power  of  an  engine,  increase  the  speed,  or  get  higher 
pressure  of  steam  ;  or  use  less  expansion. 

Q.  How  do  you  find  the  horse-power  of  an  engine? 
area  of  piston  X  M.E.P.  X  piston  speed. 
33,000. 

Q.  Which  has  the  most  friction,  a  perfectly  fitted,  or  an  im- 
perfectly fitted  valve  or  bearing?  A.  An  imperfect  one. 


650  HANDBOOK  ON  ENGINEERING  . 

Q.  How  hot  can  you  get  water  under  atmospheric  pressure  with 
exhaust  steam?  A.  212°. 

Q.  Does  pressure  have  any  influence  on  the  boiling  point?  A. 
Yes. 

Q.  Which  do  you  think  is  the  best  economy,  to  run  with  your 
throttle  wide  open  or  partly  shut?  A.  Always  have  the  throttle 
wide  open  on  a  governor  engine. 

Q.  At  what  temperature  has  iron  the  greatest  tensile  strength? 
A.  About  600°. 

Q.  About  how  many  pounds  of  water  are  required  to  yield  one 
horse-power  with  our  best  engines?  A.  From  15  to  30. 

Q.  What  is  meant  by  atmospheric  pressure?  A.  The  weight 
of  the  atmosphere. 

Q.  What  is  the  weight  of  atmosphere  at  sea  level?  A.  14.7 
pounds  per  square  inch. 

Q.  What  is  the  coal  consumption  per  hour  per  indicated  horse- 
power? A.  Varies  from  1|  to  7  Ibs. 

Q.  What  is  the  consumption  of  coal  per  hour  on  a  square  foot 
of  grate  surface?  A.  From  10  to  12  Ibs. 

Q.  What  is  the  water  consumption  in  pounds  per  hour  per 
indicated  horse-power?  A.  From  15  to  45  Ibs. 

Q.  How  many  pounds  of  water  can  be  evaporated  with  one 
pound  of  best  soft  coal?  A.  From  7  to  10  Ibs. 

Q.  How  much  steam  will  one  cubic  inch  of  water  evaporate 
under  atmospheric  pressure?  A.  One  cubic  foot  of  stearo 
(  approximately) . 

Q.  What  is  the  weight  of  a  cubic  foot  of  fresh  water?  A. 
62.425  Ibs. 

Q.  What  is  the  weight  of  a  cubic  foot  of  wrought  iron?  A. 
480  Ibs. 

Q.  What  is  the  last  thing  to  do  at  night  before  leaving  the 
plant?  A.  Look  around  for  greasy  waste,  hot  coals,  matches,  01 
anything  which  could  fire  the  building. 


HANDBOOK    ON   ENGINEERING.  651 

Q.  What  is  the  weight  of  a  square  foot  of  one-half  inch  boiler 
plate?  A.  20  Ibs. 

Q.  How  much  wood  equals  one  ton  of  soft  coal  for  steam  pur- 
poses? A.  About  4,000  Ibs.  of  wood. 

Q.  What  is  the  source  of  all  power  in  the  steam  engine?  A. 
The  heat  stored  up  in  the  coal. 

Q.  How  is  the  heat  liberated  from  the  coal  ?  A.  By  burning 
it  —  that  is,  by  combustion. 

Q.  Of  what  does  coal  consist?  A.  Carbon,  hydrogen,  nitro- 
gen, sulphur,  oxygen  and  ash. 

Q.  What  are  the  relative  proportions  of  these  that  enter  into 
coal?  A.  There  are  different  proportions  in  different  specimens 
of  coal,  but  the  following  shows  the  average  per  cent :  Carbon, 
80  ;  hydrogen,  5  ;  nitrogen,  1 ;  sulphur,  2  ;  oxygen,  7  ;  ash,  5. 

Q.  What  must  be  mixed  with  coal  before  it  will  burn?  A. 
Air. 

Q.  Of  what  is  air  composed?  A.  It  is  composed  of  nitrogen 
and  oxygen  in  the  proportion  of  77  per  cent  nitrogen  to  23  of 
oxygen. 

Q.  What  parts  of  the  air  mix  with  what  parts  of  coal?  A. 
The  oxygen  of  the  air  mixes  with  the  carbon  and  hydrogen  of  the 
coal. 

Q.  How  much  air  must  mix  with  coal?  A.  300  cubic  feet  of 
air  for  every  pound  of  coal. 

Q.  How  many  pounds  of  air  are  required  to  burn  one  pound  of 
carbon?  A.  From  20  to  24,  generally  taken  at  24. 

Q.  How  many  pounds  of  air  to  burn  one  pound  of  hydrogen? 
A.  Thirty-six. 

Q.  Is  hydrogen  hotter  than  carbon?     A.  Yes,  41  times  hotter. 

Q.  What  part  of  the  coal  gives  out  the  most  heat?  A.  The 
hydrogen  does  part  for  part,  but  as  there  is  so  much  more  of 
carbon  than  hydrogen  in  the  coal,  we  get  the  greatest  amount  of 
heat  from  the  carbon. 


652  HANDBOOK    ON    ENGINEERING. 

Q.  In  how  many  different  ways  is  heat  transmitted?  A, 
Three,  by  radiation,  by  conduction  and  convection. 

Q.  If  the  fire  consisted  of  glowing  fuel,  show  how  the  heat 
enters  the  water  and  forms  steam  ?  A.  The  heat  from  the  glow- 
ing fuel  passes  by  radiation  through  the  air  space  above  the  fuel 
to  the  furnace  crown ;  there  it  passes  through  the  iron  of  the 
crown  by  conduction  ;  there,  it  warms  the  water  resting  on  the 
crown,  which  then  rises  and  parts  with  its  heat  to  the  colder  water 
by  conduction  till  the  whole  mass  of  water  is  heated ;  then  the 
heated  water  rises  to  the  surface  and  parts  with  its  steam,  so  a 
constant  circulation  is  maintained  by  convection, 

Q.  Of  what  does  water  consist?     A.  Oxygen  and  hydrogen. 

Q.  In  what  proportion?  A.  Eight  of  oxygen  to  one  of 
hydrogen,  by  weight. 

Q.  What  are  the  different  kinds  of  heat?  A.  Latent  heat, 
sensible  heat  and  sometimes,  total  heat. 

Q.  What  is  meant  by  latent  heat?  A.  Heat  that  does  not 
affect  the  thermometer  and  which  expends  itself  in  changing  the 
nature  of  a  body,  such  as  turning  ice  into  water  or  water  into  steam. 

Q.  Under  what  circumstances  do  bodies  get  latent  heat?  A. 
When  they  are  passing  from  a  solid  state  to  a  liquid  state,  or  from 
a  liquid  to  a  gaseous  state. 

Q.  How  can  latent  heat  be  recovered?  A.  By  bringing  the 
body  back  from  a  state  of  gas  to  a  liquid,  or  from  that  of  a  liquid 
to  that  of  a  solid. 

Q.  What  is  meant  by  a  thermal  unit?  A.  The  heat  necessary 
to  raise  one  pound  of  water,  at  any  temperature — one  degree 
Fan. 

Q.  If  the  power  is  in  coal,  why  should  we  use  steam?  A.  Be- 
cause, steam  has  some  properties  which  make  it  an  invaluable 
agent  for  applying  the  energy  of  the  heat  to  the  engine. 

Q.  What  is  steam  ?  A.  It  is  an  invisible  vapor  generated 
from  water  by  the  application  of  heat. 

Q.  What  are  the  properties  which  make  it  so  valuable  to  us  ? 


HANDBOOK    ON    ENGINEERING.  653 

A.  1.  The  ease  with  which  we  can  condense  it.  2.  Its  great 
expansive  power.  3.  The  small  space  it  occupies  when  con- 
densed. 

Q.  Why  do  you  condense  the  steam?  A.  To  form  a  vacuum 
and  so  destroy  the  back  pressure  that  would  otherwise  be  on  the 
piston,  and  thus  get  more  useful  work  out  of  the  steam. 

Q.  What  is  vacuum?     A.  A  space  void  of  air. 

Q.  How  do  you  maintain  a  vacuum?  A.  By  the  steam  used 
being  constantly  condensed  by  the  cold  water  or  cold  tubes,  and 
the  air  pump  constantly  clearing  the  condenser  of  air. 

Q.  Why  does  condensing  the  used  steam  form  a  vacuum?  A. 
Because  a  cubic  foot  of  steam  at  atmospheric  pressure  shrinks 
into  about  a  cubic  inch  of  water. 

Q.  What  do  you  understand  by  the  term  horse-power?  A.  A 
horse-power  is  equivalent  to  raising  33,000  Ibs.  one  foot  per  min- 
ute, or  550  Ibs.  raised  one  foot  per  second. 

Q.  What  do  you  understand  by  lead  on  an  engine's  valve?  A. 
Lead  on  a  valve  is  the  admission  of  steam  into  the  cylinder  be- 
fore the  piston  starts  its  stroke. 

Q.  What  is  the  clearance  of  a  cylinder  as  the  term  is  applied 
at  the  present  timer  A.  Clearance  is  the  space  between  the 
cylinder  head  and  the  piston  head,  with  ports  included. 

Q.  What  are  considered  the  greatest  improvements  on  the 
stationary  engine  in  the  last  forty  years?  Ac  The  governor,  the 
Corliss  valve  gear,  and  the  triple  expansion  engine. 

Q.  What  is  meant  by  triple  expansion  engine ?  A.  A  triple 
expansion  engine  has  three  cylinders,  using  the  steam  expansively 
in  each  one. 

Q.  Is  there  any  danger  of  a  well-fitted  and  tightly-keyed  fly- 
wheel coming  loose?  A.  Yes  ;  water  in  the  cylinder  by  produc- 
ing a  heavy  jar  would  tend  to  loosen  a  fly-wheel  and  frequently 
reversing  an  engine  under  a  load  arid  high  speed,  would  tend  to 
produce  the  same  effect. 


654  HANDBOOK   ON    ENGINEERING. 

Q.  What  is  a  condenser  as  applied  to  an  engine  ?  A.  The  con- 
denser is  a  receptacle  into  which  the  exhaust  steam  enters  and  is 
there  condensed. 

Q.  What  are  the  principles  which  distinguish  a  high-pressure 
from  a  low-pressure  engine?  A.  Where  no  condenser  is  used  and 
the  exhaust  steam  is  open  to  the  atmosphere  it  is  high  pressure. 

Q.  About  how  much  gain  is  there  by  using  the  condenser?  A. 
17  to  25  per  cent,  where  cost  of  water  is  not  figured. 

Q.  What  do  you  understand  by  the  use  of  steam  expansively? 
A.  Where  steam  admitted  at  a  certain  pressure  is  cut  off  and 
allowed  to  expand  to  a  lower  pressure. 

Q.  How  many  inches  of  vacuum  give  the  best  results  in  a  con- 
densing engine?  A.  Usually  considered  25". 

Q.  What  is  meant  by  a  horizontal  tandem  engine?  A.  One 
cylinder  being  behind  the  other,  with  two  pistons  on  same  rod. 

Q.  What  is  a  Corliss  valve  gear  ?  A.  (Describe  the  half  moon, 
or  crab-claw  gear,  or  oval-arm  gear  with  dash  pots.) 

Q.  From  what  cause  do  belts  have  the  power  to  drive  shafting? 
A.  By  friction  or  adhesion. 

Q.  What  do  you  understand  by  lap?  A.  Outside  lap  is  that 
portion  of  valve  which  extends  beyond  the  ports  when  valve  is 
placed  on  the  center  of  travel ;  and  inside  lap  is  that  portion  of 
valves  which  projects  -over  the  ports  on  the  inside  or  towards  the 
middle  of  valve. 

Q.  What  is  the  use  of  inside  lap?  A.  To  give  the  engine 
compression. 

Q.  Where  is  the  dead  center  of  an  engine?  A.  The  point 
where  the  crank  and  the  piston  rod  are  in  the  same  right  line. 

Q.  In  what  position  would  you  place  an  engine  to  take  up  any 
lost  motion  of  the  reciprocating  parts  ?  A.  Place  the  engine  in 
the  position  where  the  least  wear  takes  place  on  the  journals. 
That  is,  in  taking  up  the  wear  of  crank-pin  brasses,  place  the 
engine  on  either  dead  center,  as  when  running,  there  is  little  wear 


HANDBOOK    ON    ENGINEERING.  655 

upon  the  crank-pin  at  these  points.  If  taking  up  the  cross-head 
pin  brasses  —  without  disconnecting  and  swinging  the  rod  — 
place  the  engine  at  half  stroke,  which  is  the  extreme  point  of 
swing  of  the  rod,  there  being  the  least  wear  on  the  brasses  and 
cross-head  pin  in  this  position. 

Q.  What  benefits  are  derived  from  using  fly-wheels  on  steam 
engines  ?  A.  The  energy  developed  in  the  cylinder  while  the  steam 
is  doing  its  work,  is  stored  up  in  the  fly-wheel,  and  given  out  by 
it  while  there  is  no  work  being  done  in  the  cylinder  —  that  is, 
when  the  engine  is  passing  the  dead  centers.  This  tends  to  keep 
the  speed  of  the  engine  shaft  steady. 

Q.  Name  several  kinds  of  reducing  motions,  as  used  in  indi- 
cator practice?  A.  The  pantograph,  the  pendulum,  the  brumbo 
pulley,  the  reducing  wheel. 

Q.  How  can  an  engineer  tell  from  an  indicator  diagram  whether 
the  piston  or  valves  are  leaking?  A.  Leaky  steam  valves  will 
cause  the  expansion  curve  to  become  convex ;  that  is,  it  will  not 
follow  hyperbolic  expansion,  and  will  also  show  increased  back 
pressure.  But  if  the  exhaust  valves  leak  also,  one  may  offset  the 
other,  and  the  indicator  diagram  would  show  no  leak.  A  leaky 
piston  can  be  detected  by  a  rapid  falling  in  the  pressure  on  the 
expansion  curve  immediately  after  the  point  of  cut-off.  It  will 
also  show  increased  back  pressure.  A  falling  in  pressure  in  the 
upper  portion  of  the  compression  curve  shows  a  leak  in  the  exhaust 
valve. 

Q.  What  would  be  the  best  method  of  treating  a  badly  scaled 
boiler,  that  was  to  be  cleaned  by  a  liberal  use  of  compound?  A. 
First,  open  the  boiler  up  and  note  where  the  loose  scale,  if  any, 
has  lodged.  Wash  out  thoroughly  and  put  in  the  required 
amount  of  compound.  While  the  boiler  is  in  service,  open  the 
blow-off  valve  for  a  few  seconds,  two  or  three  times  a  day,  to  be 
assured  that  it  does  not  become  stopped  up  with  scale.  After 
running  the  boiler  for  a  week,  shut  it  down,  and  when  the 


HANDBOOK    ON    ENGINEERING . 

pressure  is  down  and  the  boiler  cooled  off,  run  the  water  out  and 
take  off  the  hand-hole  plates.  Note  what  affect  the  compound 
has  had  on  the  scale,  and  where  the  disengaged  scale  has  lodged. 
Wash  out  thoroughly  and  use  judgment  as  to  whether  it  is  advis- 
able to  use  a  less  or  greater  quantity  of  compound,  or  to  add 
a  small  quantity  daily.  Continue  the  washing  out  at  short 
intervals,  as  many  boilers  have  been  buined  by  large  quan- 
tities of  scale  dropping  on  the  fire  sheets  and  not  being 
removed. 

Q.  What  is  an  engineer's  first  duty  upon  taking  charge  of  a 
steam  plant?  A.  The  first  duty  of  an  engineer  assuming  charge 
of  a  steam  plant  is  to  familiarize  himself  with  his  surroundings, 
ascertain  the  duty  required  of  each  and  every  piece  of  machinery 
contained  therein,  and  in  just  what  condition  each  one  is. 
Let  us  discuss  it  at  length,  assuming  that  when  just  engaged  he 
is  informed  as  to  the  nature  of  the  work  required  of  the  plant 
in  question,  namely:  Whether  it  is  a  heating  plant,  electric 
lighting,  hydraulic  or  electric  elevator,  power  station,  or  any 
other  kind  of  the  various  steam  plants  in  existence.  Of  course, 
a  great  deal  depends  upon  the  size  and  kind  of  plant  under  con- 
sideration and  the  number  of  men  employed,  hours  in  operation, 
and  some  other  things  in  general  which  most  engineers  know  of. 
He  should  first  see  just  what  his  plant  contains  "from  cellar 
to  garret,"  so  to  speak ;  whether  all  that  is  contained  has  to  run 
continually,  or  almost  so,  and  what  can  be  depended  on  in  case 
anything  should  suddenly  become  deranged  or  give  out  entirely. 
Next,  he  should  ascertain  the  general  condition  of  everything, 
going  over  each  portion  in  turn,  as  time  and  opportunity  permit, 
and  conclude  from  what  he  has  seen  how  much  longer  it  may 
be  run  safely  and  economically.  It  will  be  remembered  that  a 
piece  of  machinery  may  be  run  safely  and  yet  not  with  economy. 
So,  if  he  should  wait  for  the  safety  limit  to  be  reached, 
without  taking  other  things  into  consideration,  he  might  wait 


HANDBOOK    ON    ENGINEERING.  657 

a  long  time  and  in  so  doing  waste  many  dollars  of  his 
employer's  money  before  it  was  thought  necessary  to  reno- 
vate, repair  or  renew.  In  going  over  everything,  examining 
each  part  critically,  it  would  be  well  to  make  copious  notes,  and, 
sketches  might  be  added,  to  which  the  engineer  can  again  refer. 
It  sometimes  happens  that  engineers,  in  making  an  examination 
of  machinery,  do  not  take  dimensions  or  make  sketches  of  certain 
parts,  which  have  to  be  repaired,  or  perhaps  renewed,  thinking 
that  the  next  time  the  apparatus  is  looked  at  will  do  for  that. 
Now,  it  sometimes  happens  that  the  "  next  time  "  is  the  time 
when  some  accident  occurs,  finding  him  unprepared,  causing  con- 
fusion, in  the  midst  of  which  the  making  of  sketches  and  taking 
of  dimensions  cannot  be  thought  of.  All  such  should  be  done  at 
the  first  opportunity,  and  spare  parts  of  the  different  machinery 
should  be  kept  on  hand,  especially  in  the  case  of  a  plant  which 
has  only  the  machinery  which  is  constantly  in  use.  Another  point 
of  importance  to  which  an  engineer  should  give  attention,  is  to 
ascertain  the  quantity  and  kind  of  supplies  which  are  on  hand, 
that  he  may  know  when  to  make  requisition  for  more,  and  so  not 
run  short,  as  he  otherwise  might  do.  It  is  also  important  to  see 
what  tools  the  plant  contains  and  upon  what  he  can  depend  in 
case  of  the  break -down  of  any  part  of  the  machinery.  Of  course 
all  the  above  cannot  be  done  in  one  day,  but  no  time  should  be 
lost  in  doing  all  these  things  as  early  as  possible,  for  the  sooner 
he  gets  all  the  particulars  and  details  of  his  plant  at  his 
"fingers'  ends,"  the  lighter  will  be  his  own  labors,  and  the 
more  free  will  his  mind  be  to  think  and  act  intelligently  for  the 
emergencies  of  the  future.  Therefore,  by  performing  this  first 
duty  as  early  and  thoroughly  as  possible,  the  succeeding  ones  will 
be  comparatively  easy  to  handle  and  perform,  for  the  reason  that 
he  will  be  prepared  for  them. 

Q.  Define  and  explain   the    difference    between    sensible   and 
latent  heat?     A.  The  difference  between  sensible  and  latent  heat 

42 


658  HANDBOOK    ON    ENGINEERING. 

is  explained  thus :  Sensible  heat  may  be  measured  with  a  ther- 
mometer, that  is,  it  affects  the  mercury  in  a  thermometer,  caus- 
ing it  to  rise  in  the  stem  so  that  the  degree  of  heat  may  be 
measured  on  the  graduated  scale  affixed.  Latent  heat  does  not 
affect  the  thermometer.  Bodies  get  latent  heat  when  they  are 
passing  from  a  solid  state  to  a  liquid  state,  and  also  when  passing 
from  a  liquid  to  a  gaseous  state ;  and  moreover,  this  latent  heat 
can  be  recovered  bj  bringing  a  body  back  from  a  gaseous  to  a 
liquid  state,  and  from  liquid  to  solid.  Water  is  most  com- 
monly seen  under  the  three  forms  of  matter  just  mentioned, 
namely,  solid,  ice  ;  liquid,  water  ;  gaseous,  steam.  The  following 
method  has  -been  used  to  explain  how  latent  heat  exists : 
A  quantity  of  powdered  ice  is  placed  in  a  vessel  and  brought 
into  a  very  warm  room.  As  long  as  it  remains  as  ice,  it  may  be 
any  degree  of  heat  below  32°  Fahr.,  but  the  instant  it  begins  to 
melt,  owing  to  the  heat  of  the  room,  a  thermometer  placed  in  it 
will  record  32°  Fahr.  The  thermometer  will  continue  at  32°  as  long 
as  there  is  any  ice  in  the  vessel,  but  just  as  soon  as  the  last  piece  of 
ice  has  melted  it  will  begin  to  rise,  and  continue  to  do  so  until  the 
water  boils,  when  it  will  stand  at  212°  ;  but  although  the  water 
goes  on  receiving  heat  after  this,  the  instrument  will  stand  at  212° 
until  all  the  water  has  boiled  away.  Now,  a  great  amount  of  heat 
must  have  entered  the  water  since  the  ice  began  to  melt,  but  it  has 
no  effect  on  the  thermometer,  which  continues  at  32°,  as  noted 
above  ;  the  heat  that  has  so  entered  is  called  ' '  the  latent  heat  of 
water."  The  heat  that  has  entered  the  water  from  boiling 
till  it  all  becomes  steam  is  called  the  "  latent  heat  of  steam." 
The  latent  heat  of  water  has  been  found  to  be  143°  Fahr. 
and  the  latent  heat  of  steam,  at  the  pressure  of  the  atmosphere, 
is  966°.  This  is  the  way  the  above  was  determined:  A 
quantity  of  water  at  a  temperature  of  32°  Fahr.  is  made  to 
boil,  and  the  time  taken  to  do  so  noted ;  in  this  case,  it  took  one 
hour.  The  water  must  be  kept  boiling  until  it  has  all  evaporated. 


HANDBOOK    ON    ENGINEERING.  659 

and  the  time  noted  from  boiling  till  evaporation,  which  in  this 
case  will  be  5^  hours.     Therefore, 

Temperature  of  boiling  point, '    .     .     212° 

Temperature  of  water  at  first, 32° 


Heat  that  has  entered  the  water  in  one  hour,     .     .     „     .     180° 
Number  of  hours  boiling, e     .     .         51 


900 
60 

Heat  that  has  entered  during  the  5i  hours,      .     9     .     .     960° 

From  this  we  see  that  the  heat  necessary  to  form  steam,  instead 
of  being  only  212°,  must  be  966°  +  212°  =  1178°,  or  5£  times  as 
great.  Therefore,  if  it  were  not  for  latent  heat,  we  would  require 
to  burn  5J  times  the  amount  of  coal  that  we  now  do  to  generate 
steam.  The  sensible  and  latent  heats  alter  with  the  pressure,  but 
as  the  sensible  increases  the  latent  decreases,  and,  roughly 
speaking,  the  total  heat,  or  the  sum  of  the  two,  is  the  same.  In 
connection  with  the  foregoing  questions,  we  would  recommend  the 
reader  to  spend  a  little  time  in  looking  over  the  "  steam  tables," 
and  make  comparisons  between  the  different  quantities  noted 
therein.  By  so  doing  he  will  get  an  exact  knowledge  of  the  prop- 
erties of  saturated  steam. 

Q.  Explain  the  term  tc  clearance/'  as  used  in  connection  with 
an  engine  cylinder  ?  A.  There  are  two  kinds  of  clearance,  cylinder 
clearance  and  piston  clearance .  Cylinder  clearance  means  the  space 
or  volume,  which  exists  between  the  piston  and  the  valve,  when 
the  piston  is  exactly  at  the  beginning  of  the  stroke  and  the  crank 
is  on  the  dead  center.  This  volume  can  be  found  by  taking  care- 
ful and  exact  measurements  and  making  calculations  from  them, 
but  a  more  correct  way  is  to  fill  the  space  with  water,  noting  the 
quantity  used,  and  so  make  calculations  to  find  the  cubic  con- 


660  HANDBOOK    ON    ENGINEERING. 

tents.  The  cubic  contents  of  the  clearance  space  is  a  certain  per- 
centage of  the  total  volume  of  the  cylinder  itself  and  such  clear- 
ance is  expressed  as  so  much  per  cent.  This  clearance  causes  a 
small  loss  of  steam  each  stroke,  owing  to  the  difference  between 
the  initial  and  compressive  pressure.  Piston  clearance  is  the 
space  between  the  piston  and  cylinder  head  when  the  crank  is  on 
the  dead  center.  This  clearance  is  necessary  to  prevent  the 
cylinder  head  being  knocked  out,  in  case  of  an  unusual  quantity 
of  water  gaining  entrance  to  the  cylinder  while  the  engine  is 
running  at  its  usual  speed ;  and  also  to  admit  of  the  crank-pin 
and  wrist-pin  brasses  being  keyed  up  at  certain  intervals.  The 
way  to  find  the  piston  clearance  of  an  engine  is  as  follows : 
First,  disconnect  the  wrist-pin  end  of  the  connecting  rod  from 
the  cross-head,  and  with  a  bar  push  back  the  cross-head  until 
the  piston  strikes  the  cylinder  head ;  then  make  a  mark  with 
a  scriber  or  sharp  chisel,  on  both  the  sides  of  the  cross-head  and 
on  the  guide  in  which  the  cross-head  runs  ;  these  marks  must  be 
exactly  in  line  with  each  other  while  the  piston  is  in  the  above 
stated  position.  Next,  move  the  piston  to  the  other  end  of  the 
cylinder  till  it  strikes  the  head,  and  make  a  mark  on  the  guide 
similar  to  that  on  the  other  end,  using  the  same  mark  which  was 
made  on  the  cross-head.  The  new  mark  must  also  be  in  line  with 
this,  as  at  the  first  mentioned  end.  We  now  have  a  mark  at 
each  end  of  the  guide,  which  represents  the  place  at  which  the 
piston  strikes  the  cylinder  head,  when  they  alternately  coincide 
with  the  mark  on  the  cross-head  itself.  Now,  connect  the  rod 
to  the  cross-head  again  and  place  the  engine  or  crank  on  the  center. 
Next,  produce  or  extend  the  mark  on  the  cross-head  to  the  guide, 
this  time  using  a  pencil  instead  of  a  chisel  and  scriber.  The 
distance  between  the  new  pencil  mark  and  the  first  mark  made 
on  the  guide  is  the  amount  of  piston  clearance  which  exists  at 
that  end  of  the  cylinder.  Repeat  the  operation  on  the  other  end 
and  we  will  obtain  the  clearance  existing  there.  If  these  clear- 


HANDBOOK    ON    ENGINEERING.  661 

ances  are  not  equal,  as  indicated  by  the  marks,  make  them  so 
by  the  means  provided  for  in  the  design  of  the  piston  rod  and 
crosshead.  After  the  clearance  has  been  equalized,  the  pencil 
marks  may  be  obliterated  and  marks  similar  to  the  first  ones  may 
be  cut  in,  thus  leaving  a  permanent  mark,  which  can  be  seen  while 
the  engine  is  running,  and  from  which  can  be  determined  whether 
the  clearance  is  lessening,  and  at  which  end. 

Q.  What  is  the  pressure  of  the  atmosphere  at  the  sea  level,  and 
how  determined?  A.  The  pressure  of  the  atmosphere  is  generally 
spoken  of  as  15  Ibs.  per  square  inch,  but  as  the  pressure  of  the 
atmosphere  is  constantly  varying  at  any  one  spot,  corrections 
have  to  be  made  according  to  the  reading  of  a  barometer. 
Generally  speaking,  15  is  as  nearly  correct  as  engineers  require 
it.  The  pressure  of  the  atmosphere  can  be  ascertained  by  the 
following  experiment:  Take  a  glass  tube  about  33  inches  long, 
having  a  bore  equal  to  a  square  inch  in  section.  Let  one  end  of 
the  tube  be  closed  in  or  capped,  so  that  it  can  contain  a  fluid. 
Then  fill  it  with  pure  mercury,  carefully  expelling  any  air  bub- 
bles. When  it  is  full,  cover  the  open  end  of  the  tube  with  a  piece 
of  glass  and  invert  the  whole  tube.  Place  the  open  end  into  a 
cup  of  mercury,  the  surface  of  which  is  subject  to  the  pressure  of 
the  air,  and  then  withdraw  the  piece  of  glass.  The  mercury  in 
the  tube  will  drop  about  three  inches  and  then  stop.  When  it 
has  ceased  to  fall,  again  cover  the  end  of  the  tube  with  the  glass. 
Lift  the  tube  out  of  the  cup  and  remove  the  glass  so  that  the 
mercury  may  run  out  into  a  scale-pan  provided  for  that  purpose. 
Upon  actually  weighing  the  mercury  lately  contained  in  the  tube, 
it  will  be  found  to  weigh  14.7  Ibs.  The  mercury  will  stop  falling 
in  the  tube  at  30  inches,  or  at  the  sea  level.  Hence,  we  know 
that  the  atmosphere  balances,  or  exerts  a  pressure  of  14. Tibs, 
per  square  inch  at  the  sea  level. 

Q.  Upon  what  does  the  efficiency  of  a  surface  condenser  de* 
pend?  A.  The  efficiency  of  a  surface  condenser  depends  upon: 


662  HANDBOOK    ON    ENGINEERING. 

1st,  the  proper  amount  of  cooling  surface  ;  2d,  the  rapidity  with 
which  the  water  is  made  to  circulate  through  the  tubes ;  3d,  the 
water  being  made  to  flow  in  an  opposite  direction  to  the  steam. 
The  temperature  of  the  circulating  water  also  has  a  bearing  on 
the  question,  as  it  is  obvious  that  the  colder  the  water  the  more 
effective  it  will  be  in  condensing  the  steam. 

Q.  A  feed  pump  has  a  steam  cylinder  of  6  inches  in  diameter, 
and  water  cylinder  of  4  inches  diameter ;  assuming  the  steam 
pressure  carried  to  be  80  Ibs.  per  square  inch  throughout  the 
stroke,  what  will  be  the  balancing  pressure  per  square  inch 
against  the  water  piston,  friction  being  entirely  neglected,  and 
gauge  pressure  being  used?  A.  In  this  question,  we  first  find 
the  area,  the  number  of  square  inches  contained  in  the  steam 
piston.  Thus :  The  diameter  =  6  in.  and  62  x  .7854  =  the  area. 
Worked  out  it  appears  thus:  62  means  that  6  is  to  be 
squared,  or  multiplied  by  itself,  or  6  x  6  =  36  square  inches, 
and  36  square  inches  multiplied  by  the  constant  .7854  = 
28.27  square  inches  area  contained  in  the  steam  piston. 
Since  the  pressure  is  stated  to  be  80  Ibs.  per  square  inch,  then 
28.2 7  x  80  =  total  pressure  on  the  piston  in  pounds,  or  2261.60 
Ibs.  Now,  we  will  find  the  area  of  the  water  piston,  which  is  4 
inches  in  diameter,  42  x  .7854  =  12.5664  square  inches  contained 
in  the  water  piston.  Therefore,  the  water  piston,  with  an  area 
of  12.56  sq.  in.,  has  to  have  a  resistance  against  which  it  will  act 
of  2261.60  Ibs.,  in  order  to  balance  the  pressure  against  the 
steam  piston.  Hence,  the  pressure  per  square  inch  can  be  found 
by  dividing  2261.60,  or  2261.60  divided  by  12.56  ==  180  Ibs.  per 
square  inch,  the  balancing  pressure  on  the  4-inch  water  piston. 

Q.  State  what  you  consider  a  good  standard  of  strength  for 
steel  boiler  plate?  A.  The  American  Boiler  Makers'  standard, 
as  used,  is  as  follows :  Tensile  strength,  from  55,000  to  60,000 
Ibs.  per  square  inch  section ;  elongation  in  8  inches,  20  per  cent 
for  plates  |  inch  thick  and  under;  22  per  cent  for  plates  f  to  | 


HANDBOOK    ON    ENGINEERING.  663 

inches ;  25  per  cent  for  plates  J  inch  and  under ;  the  specimen 
test  piece  must  bend  back  on  itself  when  cold,  without  showing 
signs  of  fracture ;  for  plates  over  |  inch  thick,  specimens  must 
withstand  bending  180°  (or  half  way)  round  a  mandrel  1J  times 
the  thickness  of  the  plate.  The  chemical  requirements  are  as 
follows:  Phosphorus,  not  over  .04  per  cent;  sulphur,  not  over 
.03  per  cent. 

Q.  What  is  meant  by  the  heating  surface  of  a  boiler?  A.  The 
heating  surface  of  a  boiler  is  that  surface  of  plates  or  tubes  on 
one  side  of  which  is  water,  and  on  the  other,  hot  gases.  It  has 
been  decided  that  the  surface  next  the  water  shall  be  reckoned, 
the  value  to  be  given  in  square  feet.  In  a  fire  tube,  or  tubular 
boiler,  it  will  include  the  under  side  of  the  shell  from  fire-line  to 
fire-line  (usually  about  one-half  of  it),  the  tubes  and  such  part  of 
the  back-tube  sheet  as  is  below  the  back  arch  and  not  taken  up 
by  the  tube  ends.  For  a  water-tube  boiler,  the  heating  sur- 
face will  include  the  tubes,  such  part  of  the  headers  as  are 
in  contact  with  the  hot  gases,  and  the  lower  part  (about  one-* 
half)  of  the  steam  drum.  In  calculating  the  heating  surface, 
none  should  be  taken  which  has  steam  on  one  side  and  hot  gases 
on  the  other,  as  such  parts  tend  to  superheat  the  steam,  and  are 
known  as  superheating  surfaces. 

Q.  What  is  a  boiler  horse-power?  A.  A  boiler  horse-power 
has  been  recently  defined  as  the  evaporation  of  34J  pounds  of 
water  per  hour  from  a  feed  water  temperature  of  212°  Fahr. 
into  steam  at  a  temperature  of  212°  Fahr.,  and  at  a  pressure  of 
one  atmosphere.  Under  these  conditions  each  pound  of  water 
evaporated  will  take  up  966  heat  units,  and  the  34|  Ibs.  will  take 
34J  x  966  — 33,327  heat  units  per  hour.  Hence,  to  find  the 
horse-power  of  a  boiler,  it  is  necessary  to  find  the  heat  units 
delivered  per  hour  to  the  water  and  divide  that  number  by  33,327. 

Q.  What  will  be  the  heating  surface  of  a  fire-tube  boiler  6 
feet  in  diameter,  having  150  tubes  3  inches  in  diameter  and  15 


664  HANDBOOK    ON    ENGINEERING. 

feet  long?  A.  Each  tube  will  have  a  heating  surface  equal  to  its 
outside  area,  since  the  water  is  on  the  outside  of  the  tubes.  The 
area  of  a  cylinder  3  in.  in  diameter  and  15  ft.  long  will  be  the 
circumference  times  the  length ;  3  in.  =  1  ft.  and  the  circumfer- 
ence =  3.1416  x£  =  .7854  ft.;  this,  times  the  length  15  ft. 
—  11.78  sq.  ft.  for  one  tube ;  for  150  tubes,  it  will  be  150  times 
that  =  1767  sq.  ft.  The  lower  half  of  the  shell  is  usually  con- 
sidered as  heating  surface.  The  circumference  of  a  circle  6  ft.  in 
diameter  is  6x3.1416  =  18.85  ft.  and  the  area  of  the  shell  = 
18.85x15  =  282. 75  sq.  ft.  Half  this  will  be  141.37  sq.  ft. 
For  the  back  end  or  tube  plate,  the  total  area  will  be  the  diameter 
squared  times  .7854  =  62  x  .7854  sa  28.27  sq.  ft. ;  -f  of  this  will 
be  below  the  arch,  and  f  of  28.27  =  18.85  sq.  ft.  From  this 
must  be  subtracted  the  area  of  the  ends  of  the  tubes.  The  end 
area  of  one  tube  is  Q)2  x  .7854  =  .049  sq.  ft.,  and  for  150 
tubes  it  is  150  times  that,  or  7.35  sq.  ft.  The  heating  surface  of 
the  tube  plate  will  then  be  18.85  minus  7.35  =  11.5  sq.  ft.  The 
'front  tube  plate  is  not  considered,  because  the  gases  are  cooled 
too  much  to  be  effective  by  the  time  they  have  passed  through 
the  tubes.  The  total  heating  surface  is  1767  +  141.37  +  11.5 
=  1919.87  sq.  ft. 

Q.  On  what  does  the  efficiency  of  a  boiler  depend?  A.  The 
efficiency  of  any  piece  of  machinery  is  the  ratio  of  the  energy  made 
useful  to  that  furnished.  The  object  of  the  boiler  is  to  make  steam  ; 
hence,  the  enegy  used  is  that  which  has  gone  into  the  steam.  The 
proportion  of  the  heat  generated  in  the  furnace  which  is  transferred 
to  the  steam,  will  depend  on  the  thickness  of  the  plates  of  the 
boiler,  on  their  condition  as  to  cleanliness,  on  the  amount  of  time 
during  which  the  gases  are  in  contact  with  the  plates  in  their 
passage  from  furnace  to  chimney,  on  the  completeness  with  which 
all  parts  of  the  gases  are  brought  in  contact  with  the  plates,  and  on 
the  temperature  of  the  hot  gases.  Evidently,  heat  will  pass  through 
a  thin  plate  more  readily  than  through  a  thick  one,  and  more 


HANDBOOK    ON    ENGINEERING.  665 

readily  through  a  clean  plate  than  through  one  on  which  a  non- 
conducting coating  of  soot  or  scale  has  formed ;  the  more  time 
available  for  the  transfer  of  heat,  the  greater  will  be  the  amount 
transferred ;  the  more  complete  the  contact  between  plates  and 
gases,  the  more  opportunity  will  there  be  for  the  transfer  of  heat, 
and  the  higher  the  temperature  of  the  gases,  the  more  rapidly 
will  the  heat  be  transferred.  To  have  a  boiler  efficient,  it  is 
necessary  to  have  plenty  of  heating  surface,  so  that  the  hot  gases 
will  have  time  for  contact,  to  keep  the  plates  clean,  to  have  good 
circulation  of  the  gases,  and  to  keep  their  temperature  high  by 
preventing  radiation  and  allowing  as  little  air  to  enter  the  furnace 
as  is  needed  for  good  combustion.  The  efficiency  of  the  furnace, 
that  is,  the  ratio  of  the  heat  generated  in  the  furnace  to  that  con- 
tained in  the  coal,  is  a  separate  matter,  though  often  the  two  are 
lumped  together.  It  depends  on  the  adaptation  of  the  furnace  to 
the  kind  and  size  of  coal  used,  on  the  size  of  the  combustion 
chamber  and  on  the  proper  firing  of  the  coal. 

Q.  On  what  its  satisfactory  working?  A.  In  order  to 
work  satisfactorily,  a  boiler  must  not  only  be  efficient,  but  must 
make  steam  rapidly,  must  make  dry  steam,  must  be  easily  fired 
and  cleaned,  and  must  be  capable  of  standing  a  considerable 
amount  of  forcing  without  serious  priming.  To  get  rapid  steam 
making,  it  is  necessary  to  have  good  circulation  of  the  water  in  the 
boiler ;  to  get  dry  steam,  plenty  of  steam  space  is  needed,  so  that 
the  steam  may  circulate  slowly  and  allow  the  water  to  drop  out  of 
it ;  easy  firing  means  a  low  fire  door  of  good  size,  and  a  rather 
short  grate ;  easy  cleaning  means  accessible  parts,  good  sized 
man-holes,  good  sized  and  well  placed  hand-holes,  a  large  blow- 
off  and  a  short  boiler ;  the  prevention  of  priming  when  carrying 
an  overload  is  a  difficult  matter ;  the  tendency  to  such  an  occur- 
rence depends  largely  on  the  feed-water  used ;  plenty  of  steam 
space  and  good  circulation  are  helpful,  but  some  waters  will  foam 
in  spite  of  all  precautions. 


666  HANDBOOK    ON    ENGINEERING. 

Q.  Suppose  a  slide  valve  cutting  off  at  £  stroke,  and  a  |  cut- 
off is  desired,  how  would  you  proceed?  A.  Put  on  a  new  valve 
with  more  outside  lap.  This  would  require  a  greater  travel  of  the 
valve,  and  therefore  would  increase  the  throw  of  the  eccentric, 
also. 

Q.  Which  requires  the  greater  outside  lap,  cutting  off  at  T9^  oi 
the  stroke,  or  cutting  off  at  |?  A.  Cutting  off  at  T9¥.  The 
earlier  the  cut-off,  the  greater  should  be  the  outside  lap. 

Q.  Are  all  plain  slide  valves  made  alike,  as  regards  the  exhaust 
cavity  of  the  valve?  A.  No  ;  sometimes  they  are  made  '•'  line  and 
line  "  inside,  that  is,  the  width  of  the  exhaust  cavity  is  equal  to 
the  distance  between  the  inner  edges  of  the  two  steam  ports ;  and 
again,  the  width  of  the  exhaust  cavity  is  made  greater  or  less  than 
this  distance,  according  as  an  earlier  or  later  release  is  desired. 

Q.  What  is  the  effect  of  giving  inside  lap  to  a  slide  valve?  A. 
It  delays  the  release  and  increases  the  compression. 

Q.  What  is  the  effect  of  giving  inside  lead  to  a  slide  valve? 
A.  It  gives  an  early  release  and  decreases  the  compression. 

Q.  Suppose  a  simple  slide  valve  engine  with  a  fly-ball  governor, 
and  the  governor  belt  should  break  or  slip  off,  what  would 
happen?  A.  If  it  were  a  plain  governor  the  engine  would  race  ; 
but  if  a  governor  with  an  automatic  stop,  the  engine  would  slow 
down  and  stop. 

Q.  What  two  forces  are  opposed  to  each  other  in  a  case  of  fly- 
ball  governor?  A.  Centrifugal  force,  tending  to  throw  the  balls 
away  from  the  governor  staff,  and  the  force  of  gravity,  tending  to 
draw  the  balls  to  the  staff. 

Q.  What  other  name  is  given  to  a  fly-ball  governor?  A.  It  is 
also  called  a  throttling  governor,  because  the  steam  in  passing 
through  the  governor  valve  is  throttled,  choked,  or  wire- 
drawn. 

Q.  Are  all  fly-ball  governors  throttling  governors?  A.  No; 
the  governor  of  a  Porter-Allen  engine  and  those  of  all  Corliss 


HANDBOOK    ON    ENGINEERING.  667 

engines,  while  of  the  fly-ball  type,  are  not  throttling  governors, 
because  the  steam  does  not  pass  through  them. 

Q.  If  the  governor  shaft  of  a  fly-ball  governor  on  a  plain  slide- 
valve  engine  should  break,  could  the  engine  be  run?  A.  Yes; 
by  regulating  the  speed  of  the  engine  by  hand  at  the  throttle- 
valve. 

Q.  Describe  an  automatic  cut-off  engine?  A.  In  this  class  of 
engines,  as  the  load  on  the  engine  becomes  greater  or  less,  the 
steam  entering  the  cylinder  is  cut  off  later  or  earlier,  and  it  is 
done  through  a  fly-ball  governor  in  the  case  of  a  Corliss  engine, 
or  through  a  shaft-governor  or  regulator  in  the  case  of  a  high- 
speed engine. 

Q.  In  an  automatic  cut-off  high-speed  engine  with  shaft-gov- 
ernor, is  the  eccentric  fastened  to  the  shaft?  A.  It  is  not.  It 
is  so  arranged  as  to  move  freely  across  the  shaft,  in  order  to  per- 
mit the  center  of  the  eccentric  to  approach  or  to  recede  from  the 
center  of  the  shaft,  according  as  the  load  on  the  engine  decreases 
or  is  increased.  And  herein  lies  the  chief  difference  between  a 
plain  slide-valve  and  an  automatic  cut-off  slide-valve  engine. 

Q.  If  the  connecting  rod  of  an  engine  had  box  liners  at  both 
ends  and  in  taking  it  down  the  liners  were  all  mixed  up,  how 
could  the  length  of  the  rod  from  center  to  center  of  boxes  be 
found?  A.  Put  the  cross-head  in  the  middle  of  its  stroke  — 
after  finding  the  piston  striking  points  —  and  then  measure  from 
the  center  of  the  cross-head  wrist  to  the  center  of  the  main  shaft. 
If  the  piston  clearance  at  both  ends  of  the  cylinder  is  known,  the 
piston  may  be  pushed  to  the  crank  end  of  the  cylinder  until  it 
touches  the  head,  and  the  distance  from  the  center  of  the  cross- 
head  wrist  to  the  center  of  the  main  shaft  found,  to  which  should 
be  added  the  length  or  throw  of  the  crank,  and  also  the  piston 
clearance  at  the  crank  end  of  the  cylinder. 

Q.  But  suppose  it  were  more  convenient  to  push  the  piston  to 
the  head  end  of  the  cylinder,  what  then?  A.  Find  the  distance 


668  HANDBOOK    ON    ENGINEERING. 

from  the  center  of  cross-head  wrist  to  center  of  main  shaft  and 
deduct  the  throw  of  the  crank,  and  also  the  clearance. 

Q.  How  is  the  length  of  the  valve  stem  and  of  the  eccentric 
rod  found  for  a  plain  slide  valve  engine  having  a  rock  shaft?  A. 
If  the  motion  of  the  slide  valve  is  parallel  with  the  motion  of  the 
piston,  the  length  of  the  valve  stem  may  be  found  by  measuring 
in  a  horizontal  line  from  the  center  of  the  valve  seat  to  the  center 
of  the  rock  shaft ;  and  for  the  eccentric  rod  by  measuring  from 
the  center  of  the  rock  shaft,  horizontally,  to  the  center  of  the 
main  shaft,  which  would  include  one-half  the  yoke. 

Q.  What  is  a  direct,  and  also  an  indirect  valve  motion?  A. 
When  there  is  no  rock  shaft  between  the  eccentric  and  the  valve 
to  compound  the  motion,  it  is  called  "  direct/'  and  when  a  rock 
shaft  intervenes,  it  is  called  an  tc  indirect  "  valve  motion. 

Q.  Is  the  valve  motion  of  a  Corliss  engine  direct  or  indirect? 
A.  It  is  direct. 

Q.  How  so ;  it  has  a  rock  shaft  between  the  eccentric  and 
the  wrist  plate?  A.  Even  so,  it  is  a  direct  valve  motion;  because 
all  connections  to  the  rock-shaft  arm  are  above  the  center  of  the 
shaft,  consequently,  the  motion  is  simple  and  not  compound. 

Q.  When  is  an  engine  said  to  "  run  under,"  and  when  to  "  run 
over?  "  A.  When  the  crank  pin  is  above  the  center  of  the  main 
shaft  and  the  pin  moves  towards  the  cylinder,  the  engine  is  said 
to  "  run  under ;  "  and  when  it  moves  away  from  the  cylinder,  the 
engine  is  said  to  "  run  over." 

Q.  What  is  meant  by  lead  of  valve,  and  what  is  it  for?  A. 
Lead  is  the  amount  that  the  port  is  open  to  steam  when  the  crank 
is  on  its  center.  It  is  given  in  order  to  allow  the  full  pressure  of 
steam  to  come  on  the  piston  at  the  beginning  of  the  stroke,  and 
to  provide  a  cushion  for  the  piston. 

Q.  Could  not  cushion  for  the  piston  be  obtained  in  some  other 
manner?  A.  Yes,  by  producing  compression  by  an  early  closing 
of  the  exhaust. 


HANDBOOK    ON    ENGINEERING.  669 

Q.  Suppose  a  slide  valve  had  f "  lap  and  no  lead,  and  it  was 
desired  to  give  it  -+-'  lead,  how  should  it  be  done?  A.  By  mov- 
ing the  eccentric. 

Q.  Why  could  it  not  be  done  by  altering  the  length  of  the 
eccentric  rod  ?  A.  Because  the  eccentric  rod  does  not  establish 
the  amount  of  lead ;  it  simply  equalizes  the  lead  given  by 
moving  eccentric. 

Q.  How  would  you  test  the  piston  of  a  steam  engine  to  see 
whether  it  was  steam-tight  or  not?  A.  Put  the  crank  on  the 
outboard  center ;  remove  the  cylinder  head  on  the  head  end ; 
block  the  cross-head  and  admit  steam  to  the  crank-end  of 
cylinder  and  note  the  effect.  The  fly-wheel,  or  the  cross-head 
may  be  securely  blocked  and  the  piston  tested  in  this  manner  at 
different  points  in  the  stroke. 

Q .  W  hy  are  two  eccentrics  and  two  wrist  plates  put  on  some  Corliss 
engines  ?  A.  One  eccentric  is  for  the  induction  valves  to  lengthen 
the  range  of  the  cut-off  ;  the  other  for  the  exhaust  valves  to  admit 
of  early  release,  without  excessive  compression.  With  a  Corliss 
engine  having  but  one  eccentric,  the  limit  of  cut-off  is  at  less  than 
one-half  stroke,  but  with  two  eccentrics  the  cut-off  may  be  still 
later  in  the  stroke,"  and  still  release  the  steam  at  the  proper  time. 

Q.  What  is  meant  by  a  ic  blocked  up  "  governor  en  a  Corliss 
engine?  A.  When  the  safety  stop  is  "in, "the  governor  is  said 
to  be  blocked  up. 

Q.  With  a  blocked  up  governor,  suppose  the  main  driving  belt 
should  break,  what  would  be  the  result?  A.  The  engine  would 
race  and  would,  perhaps,  be  wrecked. 

Q.  What  is  meant  by  the  fire  line  of  a  horizontal  cylindrical 
boiler  ?  A.  It  is  the  height  to  which  the  shell  is  exposed  to  the 
action  of  the  flames. 

Q.  How  high  should  the  fire  line  be  run?  A.  It  maybe  run  as 
high  as  the  lower  gauge  cock  water  level,  although  it  is  frequently 
run  no  higher  than  the  top  row  of  flues. 


670  HANDBOOK    ON    ENGINEERING. 

Q.  What  causes  a  chimney  or  smoke-stack  to  draw?  A.  The 
difference  in  the  temperature  of  the  air  inside  the  chimney  and 
that  outside.  The  air  inside  expands  and  exerts  less  pressure 
than  the  outside  air,  which  rushes  in  to  equalize  the  pressure. 

Q.  What  does  the  amount  of  grate  surface  determine?  A.  It 
determines  the  amount  of  coal  that  can  be  burned  per  hour,  and 
consequently,  the  amount  of  steam  that  can  be  generated. 

Q.  What  is  the  object  in  giving  a  slide  valve  outside  lap?  A. 
To  save  steam  by  cutting  off  the  flow  of  steam  into  the  cylinder 
before  the  piston  reaches  the  end  of  its  stroke.  For  example: 
With  24  in.  stroke  of  piston  and  |  cut-off,  the  flow  of  steam  to 
the  piston  is  cut  off  when  the  piston  has  moved  15  inches  and  it 
is  driven  the  remaining  9  inches  by  the  expansive  force  of  the 
steam. 

Q.  What  amount  of  refrigerating  water  is  required  for  a  con- 
denser? A.  For  a  surface  condenser  about  50  times,  and  for  a 
jet  condenser  30  times  the  amount  of  water  evaporated  in  the 
boiler ;  more  or  less  than  these  quantities  being  required  accord- 
ing to  the  temperature  of  the  exhaust  steam. 

Q.  Suppose  your  condenser  was  out  of  order  and  undergoing 
repairs,  could  you  run  the  engine?  A.  Yes;  by  attaching  an 
exhaust  pipe  to  the  engine  and  exhausting  into  the  atmosphere. 

Q.  With  a  lever  safety  valve,  should  the  end  of  the  valve  stem 
upon  which  the  lever  rests,  be  square  or  concave?  A.  Neither 
one;  it  should  be  pointed,  so  that  the  lever  will  always  bear 
directly  on  a  line  with  the  center  of  the  valve  stem. 

Q.  What  is  the  proper  proportion  of  a  safety  valve  lever?  A. 
About  7  to  1 ;  that  is,  if  the  distance  from  the  center  of  the 
valve  to  the  fulcrum  is  1  inch,  the  distance  from  the  center  of  the 
valve  to  the  end  of  the  long  arm  of  the  lever  should  be  about  7 
inches. 

Q.  How  should  the  grates  be  set  in  a  boiler  furnace?  A. 
They  should  be  set  level,  because  this  plan  will  enable  the  fire- 


HANDBOOK    ON    ENGINEERING. 

man  to  more  easily  carry  a  bed  of  fuel  of  uniform  depth ;  besides, 
it  is  less  laborious  to  clean  the  fire  than  when  the  grates  are  lower 
at  the  bridge  wall. 

Q.  What  is  momentum?  A.  It  is  the  product  of  the  mass  or 
bulk  of  a  moving  body,  taken  in  pounds  or  tons,  multiplied  by  the 
velocity  of  the  moving  mass,  generally  taken  in  feet  per  second. 

Q.  Will  an  injector  work  at  the  same  steam  pressure  wnen  it 
lifts  the  water  as  when  the  water  flows  to  it  under  pressure  ?  A. 
No ;  when  the  water  flows  to  an  injector  under  pressure  it  will 
work  down  to  the  lowest  steam  pressures,  but  when  lifting  the 
water  it  requires  a  steam  pressure  of  ten  pounds  or  over  to  work 
the  injector. 

Q.  What  is  the  greatest  height  to  which  an  injector  will  lift 
water?  A.  That  depends  upon  the  starting  steam  pressure. 
There  are  injectors  that  will  lift  water  two  feet  with  10  Ibs. 
steam  pressure,  five  feet  with  30  Ibs.,  and  from  12  to  25  feet  with 
60  Ibs.  and  over. 

Q.  If  the  pulley  on  the  main  shaft  of  an  engine  driving  a  fly- 
ball  governor  be  reduced  in  diameter,  what  affect  will  it  have  on 
the  speed  of  the  engine?  A.  The  speed  of  the  engine  will  be 
increased. 

Q.  Which  is  the  greater,  the  bursting  or  the  collapsing  pressure 
of  a  boiler  tube?  A.  A  boiler  tube  will  collapse  under  less  pres- 
sure than  would  be  required  to  burst  it. 

Q.  Should  a  horizontal  externally  fired  boiler  be  set  level  or 
with  a  pitch?  A.  It  is  customary  to  set  such  a  boiler  one  inch 
lower  at  the  end  to  which  the  blow-off  pipe  is  attached,  in  order 
to  drain  the  boiler  readily. 

Q.  In  a  slide  valve  engine  with  a  connecting  rod,  will  the  valve 
cut  off  the  same  at  both  ends  of  the  stroke  if  it  has  equal  lap  and 
lead?  A.  No  ;  owing  to  the  angularity  of  the  connecting  rod. 

Q.  Is  it  proper  to  close  the  damper  with  a  banked  fire?  A. 
The  damper  should  never  be  closed  tightly  while  there  is  fire. 


672 


HANDBOOK    ON    ENGINEERING. 


CHAPTER     XXIII. 
INSTRUCTIONS  FOR  LINING   UP  EXTENSION  TO  LINE   SHAFT. 

The  erection  of  a  line  shaft,  or  an  extension  to  one,  is  a 
job  that  should  have  the  services  of  a  competent  millwright  or 
machinist,  as  it  is  one  calling  for  experience  and  considerable 
skill. 

The  following  drawing  will  serve  to  illustrate  the  operation.  A 
linen  line  or  fine  wire  should  be  stretched  beneath  the  shaft  and 
parallel  to  it,  and  extending  beyond  the  termination  of  the 
extension. 


4JL, 


L1NE 


VA 

Fig.  311.    Method  of  lining  up  shafting. 

To  set  the  line  parallel  to  the  main  line  shaft,  hang  the  plumb- 
bobs  A  A  over  the  shaft,  as  shown  in  the  sketch,  and  then  adjust 
the  line  until  it  just  touches  the  lines  supporting  the  bobs,  with- 
out disturbing  their  position.  If  the  plumb-bobs  give  trouble  by 
swaying,  set  pails  of  water  so  that  the  bobs  will  be  immersed  ; 
this  will  stop  the  swaying  without  destroying  their  truth.  The 
plumb-bobs  may  just  as  well  be  old  nuts  or  similar  pieces  of  iron, 


HANDBOOK    ON    ENGINEERING.  673 

A 

as  the  regulation  type,  since  the  result  will  be  exactly  the   same. 
After  getting  the  line  adjusted  to  the    desired   position,  suspend 
the  plumb-bobs  A  A   along  the  direction  of  the  extension,  so  that 
their  supporting  cords  will  just  touch  the  line  without  disturbing  it. 
The  new  section  of  the  shaft  is  now  brought  in  position  sideways 
until  it  also  touches  the  cords  of  the  plumb-bobs  ^4  A  ,  which,  of 
course,  locates  it  parallel  with  the  main  shaft  in  a  horizontal  plane. 
To  get  it  to  the  right  height,  enter  the  shaft  coupling  of  the  new 
part  into  coupling  of  the  main  shaft,  and  then  adjust  until  the 
shaft  shows  level  when  tested  with  an  accurate   spirit  level.     A 
level  suitable  for  this  work  should  be  of  iron  and  planed  on  the 
under  side  with  a  V-groove,  which  will  always  locate  it  parallel 
with  the  shaft  when  testing  it.     Before  leveling  the  new  part  of 
the  shaft,  it  will  be  necessary  to  try  the  shaft  already  in  position, 
as  it  may  not  be  level.     If  found    "  out  "    it  should  be  leveled, 
but  sometimes  this  will  not  be  possible  or  feasible,  in  which  case 
it  will  be  necessary  to  set  the  new  part  at  the  same  inclination. 
To  do  this,  test  the  main  shaft  and  find  how  much  it  is  out,  and 
adjust  the  level  by  strips  of  paper  until  it  shows  "  fair."     The 
paper  should  be  secured  to  the  level  by  glue  or  other  means  and 
used  on  the  new  shaft  in  that  condition,  always  keeping  the  level 
with  the  "  packed"  end  pointing  in  the  same  direction.     After 
getting  the  new  part  in  position,  it  is  well  to  test  it  before  con- 
necting it  to  the  main  part ;  that  is,  it  should  be  turned  by  hand 
to  determine  if  the  frictional  resistance  is  excessive  or  not.     After 
connecting  with  the  main  part,  it  is  not  a  bad  idea  to  test  it  again 
by  hand,  if  possible.     With  a  long  shaft  it  may  be  necessary  to 
disconnect  the  farther  sections  and  remove   the   belts  from  the 
connected  machines.     In  this  way  a  fair  idea  of  the  frictional 
resistance  may  be  obtained.     As  before  stated,  this  work  requires 
experience  and    skill,  and  should  properly  be  done  by  one  thor- 
oughly competent  for  the  work  ;  for,  while  his  services  may  seem 
a  trifle  expensive,  it  will  usually  be  found  to  pay  better  in  the 

43 


674  HANDBOOK    ON    ENGINEERING. 

long  run,  as  the  frictional  resistance  of  an  improperly  lined  shaft 
will  quickly  consume  coal  enough  to  pay  the  difference. 

SIMPLICITY  IN  STEAM   PIPING. 

In  building  steam  power  plants,  and  especially  in  arranging 
the  piping  connections  for  them,  simplicity  is  a  characteristic  the 
value  of  which  is  often  too  little  appreciated.  It  should  be  borne 
in  mind  that  extra  valves  and  duplicate  piping  mean  a  very 
considerable  amount  of  capital  lying  at  waste  to  meet  a  contin- 
gency, which  may,  in  all  probability,  never  arise,  not  to  speak  of 
the  care  and  attention  required  to  keep  piping  and  valves  which 
are  rarely  used  in  shape  for  service.  Another  point  which  ought 
to  be  realized  in  the  design  of  piping,  is  that  every  square  foot  of 
uncovered  surface,  as  in  flanges  and  the  like,  causes  the  loss  of 
about  one  dollar  per  year  in  condensation  of  steam ,  and  each  square 
foot  of  uncovered  surface  represents  the  loss  of  nearly  one-quarter 
of  this  amount.  The  principle  of  construction  is  to  design  the 
piping  with  the  utmost  simplicity  possible  ;  without  any  double 
connections,  put  it  up  so  that  no  accidents  can  happen  to  it.  It 
is  argued  that  this  is  impossible,  but  it  is  equally  impossible  to 
insure  absolute  immunity  against  "  shut  downs,"  of  greater  or 
less  duration,  by  any  amount  of  duplex  connections,  for  even 
the  blowing  out  of  a  single  gasket  can  blow  down  a  whole  battery 
of  boilers  before  a  12 -inch  valve  can  be  closed  and  another 
opened.  With  the  more  extensive  introduction  of  high-pressure 
valves  and  fittings,  it  is  possible,  by  proper  design,  to  reduce 
the  liability  to  accident  very  nearly  to  the  point  of  absolute 
safety,  and  by  the  introduction  of  one  or  two  extra  valves,  it  is 
generally  possible  to  divide  the  plant  into  sections,  any  one  of 
which  can,  if  occasion  demands,  be  operated  independently.  No 
fixed  rules  can  be  laid  down  and  the  line  between  absolute  sim- 
plicity and  necessary  complexity  must  be  drawn  separately  for 
each  plant  with  due  regard  to  the  work  it  has  to  perform ,  but  it 


HANDBOOK    ON    ENGINEERING. 


675 


should  be  remembered  that  the  more  simple  a  plant  can  be  made 
to  accomplish  the  work  with  absolute  reliability,  the  greater  the 
achievement  in  economy  of  first  cost,  and  in  availability  and 
economy  of  operation. 


Fig.  312.    Diagram  showing  screwed  yalve  and  fittings. 


St^^rW—itt)      I      & 

T 


Fig.  313.    Diagram  showing  flanged  valye  and  fittings. 

CUTTING   PIPE  TO  ORDER. 

In  placing  orders  for  pipe,  a  diagram  should  be  made,  accord- 
ing to  above  cuts.  Great  care  should  be  taken  in  making  a 
diagram  for  large  pipe  ;  all  measurements  should  be  from  centers. 
When  flanged  fittings  are  used,  state  if  desired  drilled,  and  if 
with  bolts  and  gaskets  complete.  If  it  is  desired  that  the 


67G 


HANDBOOK    ON    ENGINEERING. 


fittings  be  made  tight,  then  mark  such  pieces  at  point  joint  is 
desired,  on  diagram. 

FEED=WATER  REQUIRED   BY   SHALL  ENGINES. 


Pressure  of  Steam 
in  Boiler,  by 
Gauge. 

Pounds  of  Water 
per     Effective 
Horse  -power  per 
Hour. 

Pressure  of  Steam 
in  Boiler,  by 
Gauge. 

Pounds  ot   Water 
per   Effective 
Horse-  power  per 
Hour. 

10 

118 

60 

75 

15 

111 

70 

71 

20 

105 

80 

68 

25 

100 

90 

65 

30 

93 

100 

63 

40 

84 

120 

61 

50 

79 

160 

58 

HEATING   FEED-WATER. 

Feed-water,  as  ^  comes  from  the  wells  or  hydrants  j  has  ordi- 
narily a  temperature  of  from  35°  in  winter  to  from  60  to  70°  in 
summer.  Much  fuel  can  be  saved  by  heating  this  water  by  the 
exhaust  steam,  whose  heat  would  otherwise  be  wasted.  Until 
quite  recently,  only  non-condensing  engines  utilized  feed -water 
heaters  but  lately  they  have  been  introduced  with  success  between 
the  cylinder  and  the  air-pump  in  condensing  engines.  The 
saving  in  fuel  due  to  heating  feed-water  is  given  on  page  680. 


RATING   BOILERS   BY   FEED-WATER. 

The  rating  of  boilers  has,  since  the  Centennial  Exposition  in 
1876,  been  generally  based  on  30  pounds  feed-water  per  hour  per 
horse-power.  This  is  a  fair  average  for  good  non-condensing  engines 
working  under  about  70  to  100  ponnds  pressure.  But  different 


HANDBOOK   ON    ENGINEERING. 


677 


pressures  and  different  rates  of  expansion  change  the  require- 
ments for  feed-water.  The  following  table  gives  Prof.  R.  H. 
Thurston's  estimate  of  the  steam  consumption  for  the  best  classes 
of  engines  in  common  use  when  of  moderate  size  and  in  good 
order : — 

WEIGHTS  OF  FEED  WATER  AND  OF  STEAM. 

NON-CONDENSING   ENGINES.  —  R.    H     T. 


Steam  Pressure. 

Lbs.  per  H.  P.  per  Hour.  —  Ratio  of  Expansion. 

Atmos- 
phere. 

Lbs.  per 
sq.  ID. 

2 

3 

4 

£ 

7 

10 

3 

45 

40 

39 

40 

40 

42 

45 

4 

60 

35 

34 

36 

36 

38 

40 

5 

75 

30 

28 

27 

26 

30 

32 

6 

90 

28 

27 

26 

25 

27 

29 

7 

105 

26 

25 

24 

23 

25 

27 

8 

120 

25 

24 

23 

22 

22 

21 

10 

150 

24 

23 

22 

21 

20 

20 

CONDENSING    ENGINES. 


2 

30 

30 

28 

28 

30 

35 

40 

3 

45 

28 

27 

27 

26 

28 

32 

4 

60 

27 

26 

25 

24 

25 

27 

5 

75 

26 

25 

25 

23 

22 

24 

6 

90 

26 

24 

24 

22 

21 

20 

8 

120 

25 

23 

23 

22 

21 

20 

10 

150 

25 

23 

22 

21 

20 

19 

Small  engines  having  greater  proportional  losses  in  friction,  in 
leaks,  in  radiation,  etc.,  and  besides  receiving  generally  less  care 


678  HANDBOOK    ON    ENGINEERING. 

in  construction  and  running  than  larger  ones,   require  more  feed 
water  (or  steam)  per  hour. 

FEED  WATER  HEATERS. 

Inattention  to  the  temperature  of  feed  water  for  boilers  is  en- 
tirely too  common,  as  the  saving  in  fuel  that  may  be  effected  by 
thoroughly  heating  the  feed  water  —  by  means  of  the  exhaust 
steam  in  a  properly  constructed  heater  —  would  be  immense,  as 
may  be  seen  from  the  following  facts :  A  pound  of  feed  water  en- 
tering a  steam  boiler  at  a  temperature  of  50°  Fahr.,  and  evapo- 
rating into  steam  of  60  Ibs.  pressure,  requires  as  much  heat  as 
would  raise  1157  Ibs.  of  water  1  degree.  A  pound  of  feed  water 
raised  from  50°  Fahr.  to  220°  Fahr.  requires  987  thermal  units 
of  heat,  which  if  absorbed  from  exhaust  steam  passing  through  a 
heater,  would  be  a  saving  of  15  per  cent  in  fuel.  Feed  water  at  a 
temperature  of  200°  Fahr.,  entering  a  boiler,  as  compared  in  point 
of  economy,  with  feed  water  at  50°,  would  effect  a  saving  of  over 
13  per  cent  in  fuel ;  and  with  a  well-constructed  heater  there  ought 
to  be  no  trouble  in  raising  the  feed  water  to  a  temperature  of  212° 
Fahr.  If  we  take  the  normal  temperature  of  the  feed  water  at  60°, 
the  temperature  of  the  heated  water  at  212°  and  the  boiler  pressure 
at  20  Ibs.,  the  total  heat  imparted  to  the  steam  in  one  case  is 
1192.5°  minus  60°  =  1132. 5°;  and  in  the  other  case,  1192.5° 
minus  212°  =  980.5°,  the  difference  being  152°,  or  a  saving  of 
152/1132.5  =  13.4  per  cent.  Supposing  the  feed  water  to  enter 
the  boiler  at  a  temperature  of  32°  Fahr.,  each  pound  of  water  will 
require  about  1200  units  of  heat  to  convert  it  into  steam,  so  that 
the  boiler  will  evaporate  between  6|  and  7^  Ibs.  of  water  per 
pound  of  coal.  The  amount  of  heat  required  to  convert  a  pound 
of  water  into  steam  varies  with  the  pressure,  as  will  be  seen  by 
the  following  table :  — 


HANDBOOK    ON    ENGINEERING. 


679 


TABLE  SHOWING  THE  UNITS  OF  HEAT  REQUIRED  TO  CONVERT  ONE  POUND 
OF  WATER,  AT  THE  TEMPERATURE  OF  32°  FAHR.,  INTO  STEAM  AT 
DIFFERENT  PRESSURES. 


Pressure  of 

Pressure  of 

Steam  in  Ibs.  per 

Units  of  Heat. 

Steam  in  Ibs.  per 

Units  of  Heat. 

Sq.  In.  by  Gauge. 

Sq.  In.  by  Gauge. 

1 

1,148 

110 

,187        ' 

10 

1,155 

120 

,189 

20 

1,161 

130 

,190 

30 

,165 

140 

,192 

40 

,169 

150 

,193 

50 

,173 

160 

,195 

60 

,176 

170 

,196 

70 

,178 

180 

,198 

80 

,181 

190 

,199 

90 

1,183 

200 

,200 

100 

1,185 

If  the  feed  water  has  any  other  temperature  the  heat  necessary 
to  convert  it  into  steam  can  easily  be  computed.  Suppose,  for 
instance,  that  its  temperature  is  65°,  and  that  it  is  to  be  converted 
into  steam  having  a  pressure  of  80  Ibs.  per  square  inch.  The 
difference  between  65  and  32  is  33;  and  subtracting  this  from 
1181  (the  number  of  units  of  heat  required  for  feed  water  hav- 
ing a  temperature  of  32°),  the  remainder,  1148,  is  the  number  of 
units  for  feed  water  with  the  given  temperature.  Yet  it  must  be 
understood  that  any  design  of  heater  that  offers  such  resistance 
to  the  free  escape  of  the  exhaust  steam  as  to  neutralize  the  gain 
that  would  otherwise  be  obtained  from  its  use,  ought  to  be 
avoided,  as  the  loss  occasioned  by  back  pressure  on  the  exhaust, 
in  many  instances,  counteracts  the  advantages  derived  from  the 
heating  of  the  feed  water. 


Feed  water  heaters   are  a   most  important  feature  of  a  good 
steam  plant.     First,  by  utilizing  the  heat   of  the   exhaust   steam 


680 


HANDBOOK    ON    ENGINEERING. 


from  the  engine  or  waste  gases  in  chimney,  the  feed  water  may  be 
heated  to  about  210°  Fahr.,  with  ease,  before  entering  boilers, 
by  this  means  saving  fuel  and  increasing  capacity  of  boiler. 
Second.  By  heating  the  water,  the  boilers  are  protected  from 
serious  and  unequal  strain,  as  the  difference  of  temperature  be- 
tween incoming  water  and  outgoing  steam  may  be  kept  about  1 10° 
(210°  to  320°).  Third.  Every  heater  must  necessarily  be  a 
water  purifier,  as  the  mud  and  lime  are  eliminated,  to  some  degree 
at  least,  before  the  water  reaches  the  boiler, by  heat. 

TABLE. 

SHOWING  GAIN  BY  USE  OF  FEED  WATER  HEATER.  PERCENTAGE  OF 
HEAT  REQUIRED  TO  HEAT  WATER  FOR  DIFFERENT  FEED  AND  BOILING 
TEMPERATURES,  AS  COMPARED  WITH  A  FEED  AND  BOILING  TEM- 
PERATURE OF  212°. 


Boiling 

•T)        •         A. 

Initial  Temperature  of  feed  water. 

IrOint. 

Fahr. 

32° 

50° 

68° 

86° 

104° 

122° 

140° 

158° 

176° 

194° 

212° 

212 

1.19 

1.17 

1.15 

1.13 

1.11 

1.10 

1.08 

.06 

1.04 

1.02 

1.00 

230 

1.20 

1.18 

1.16 

1.14 

1.12 

1.10 

1.08 

.06 

.04 

1.02 

1.01 

248 

1.20 

1.18 

1.16 

1.14 

1.13 

1.11 

1.09 

.07 

.05 

1.03 

1.01 

266 

1.21 

1.19 

1.17 

1.15 

1.13 

1.11 

1.09 

.07 

.06 

1.04 

1.02 

284 

1.21 

1.20 

1.18 

1.16 

1.14 

1.12 

1.10 

.08 

.06 

.04 

1.02 

302 

1.22 

1.20 

1.18 

1.16 

1.14 

1.12 

l.ll 

1.09 

.07 

.05 

.03 

320 

1.22 

1.21 

1.19 

1.17 

1.15 

1.13 

1.11 

1.09 

.07 

.05 

.03 

338 

1.23 

1.21 

1.19 

1.17 

1.15 

1.14 

1.12 

1.10 

.08 

.06 

.04 

356 

1.23 

1.22 

1.20 

1.18 

1.16 

1.14 

1.12 

1.10 

1.08 

.06 

.04 

374 

1.24 

1.22 

1.20 

1.18 

1.17 

1.15 

1.13 

1.11 

1.09 

.07 

.05 

392 

1.24 

1.23 

1.21 

1.19 

1.17 

1.15 

1.13 

1.11 

1.09 

1.07 

.06 

410 

1.25 

1.23 

1.22 

1.20 

1.18 

1.16 

1.14 

1.12 

1.10 

1.08 

.06 

428 

1.25 

1.24 

1.22 

1.20 

1.18 

1.16 

1.14 

1.12 

1.11 

1.09 

.07 

There  are  two  distinct  types  of  heaters  in  which  heat  is  derived 
from  exhaust  steam.  These  are  known  as  closed  and  open 
heaters.  Each  has  its  advantages  and  disadvantages.  The 
closed  heater  is  constructed  so  that  the  water  is  forced  under  pres- 


HANDBOOK    ON    ENGINEERING.  081 

sure  through  tubes  or  chambers  surrounded  by  the  exhaust  steam, 
the  heat  being  transmitted  through  the  walls  of  the  tubes  and  cham- 
bers. The  open  heater  is  a  vessel  in  which  the  feed  water  comes 
into  direct  contact  with  the  exhaust  steam,  by  spraying  or  inter- 
mingling. The  heated  water  is  pumped  hot  into  the  boiler. 
The  closed  heater  has  tbe  advantage  of  permitting  the  water  to 
pass  through  the  pump  cold  and  in  that  state  is  easily  handled. 
To  pump  hot  water  from  an  open  heater  requires  special  care  in 
piping  and  packing  the  feed  pump.  The  closed  heater,  being  a 
purifier  (if  any  lime  is  present  in  water,  a  portion  is  bound  to  be 
precipitated  by  heat),  should  be  cleaned,  a  job  about  as  difficult 
as  cleaning  a  boiler ;  or  blown  out,  which  is  never  a  satisfactory 
method.  In  the  precipitation  of  lime  by  heat,  carbonic  acid  gas 
is  set  free  and  chemists  say  that  this  gas  in  a  nascent  state  (just 
being  born)  attacks  iron  and  brass.  Whatever  the  cause,  experi- 
ence has  demonstrated  that  ordinary  wrought  iron,  steel  and 
brass,  corrode  under  this  action.  The  open  heater,  being  usually 
a  large  chamber,  is  accessible  for  cleaning  out,  and  if  made  with 
ordinary  care  will  last  a  long  time.  A  leak  in  it  is  not  a  serious 
matter,  while  a  leak  in  the  closed  heater  means  a  waste  of  hot 
water  into  the  exhaust  pipe.  The  open  heater  has,  at  times, 
been  the  cause  of  serious  mishaps.  In  it  the  steam  and  water 
mix ;  with  any  stoppage  in  exit  of  feed  water,  there  is  danger 
of  flooding  the  cylinder  of  the  steam  engine  through  exhaust 
pipe,  causing  a  wreck.  The  more  modern  forms  of  these  heaters 
and  the  experience  obtained  in  their  use  have  reduced  this 
difficulty  to  a  minimum. 

WATER. 

Pure  water  at  62°  F.  weighs  62.355  pounds  per  cubic  foot,  or 
8i  Ibs.  per  U.  S.  gallon;  7.48  gallons  equal  1  cu.  ft.  It  takes 
30  Ibs.,  or  3.6  gal.  for  each  horse-power  per  hour.  It  would  be 
difficult  to  get  at  the  total  daily  horse-power  of  steam  used  in  the 


682  HANDBOOK    ON    ENGINEERING. 

U.  S.,  but  it  reaches  into  the  billions  of  gallons  of  feed  water  per 
day.  The  importance  of  knowing  what  impurities  exist  in  most 
feed  waters,  how  these  act  on  a  boiler  and  how  they  may  be  re- 
moved is,  therefore,  patent  to  every  intelligent  engineer.  We  give 
therefore,  the  thoughts  of  some  prominent  investigators  on  the 
subject. 

Prof*  Thurston  says :  — 

"  Incrustation  and  sediment  are  deposited  in  boilers,  the  one 
by  the  precipitation  of  mineral  or  other  salts  previously  held  in 
solution  in  the  feed  water,  the  other  by  the  deposition  of  mineral 
insoluble  matters,  usually  earths,  carried  into  it  in  suspension  or 
mechanical  admixture.  Occasionably  also,  vegetable  matter  of  a 
glutinous  nature  is  held  in  solution  in  the  feed  water,  and,  pre- 
cipitated by  heat  or  concentration,  covers  the  heating  surfaces 
with  a  coating  almost  impermeable  to  heat,  and  hence,  liable  to 
cause  an  overheating  that  may  be  very  dangerous  to  the  struc- 
ture. A  powdery  mineral  deposit  sometimes  met  with  is  equally 
dangerous,  and  for  the  same  reason.  THE  ANIMAL  AND  VEGE- 
TABLE OILS  AND  GREASES  CARRIED  OVER  FROM  THE  CONDENSER  OR 
FEED  WATER  HEATER  ARE  ALSO  VERY  LIKELY  TO  CAUSE  TROUBLE. 

Only  mineral  oils  should  be  permitted  to  be  thus  introduced,  and 
that  in  minimum  quantity.  Both  the  efficiency  and  safety  of  the 
boiler  are  endangered  by  any  of  these  deposits. 

"  The  amount  of  the  foreign  matter  brought  into  the  steam 
boiler  is  often  enormously  great.  A  boiler  of  100  horse-power 
uses,  as  an  average,  probably  a  ton  and  a  half  of  water  per 
hour,  or  not  far  from  400  tons  per  month,  steaming  ten  hours 
per  day ;  and  even  with  the  water  as  pure  as  the  Croton  at 
New  York,  receives  90  pounds  of  mineral  matter,  and  from 
many  spring  waters  a  ton,  which  must  be  either  blown  out  or 
deposited.  These  impurities  are  usually  either  calcium  carbon- 
ate or  calcium  sulphate,  or  a  mixture ;  the  first  is  most  com- 
mon on  land,  the  second  at  sea.  Organic  matters  often 


HANDBOOK    ON    ENGINEERING.  683 

harden  these  mineral  scales  and  make  them  more  difficult  of 
removal. 

"The  only  positive  and  certain  remedy  for  incrustation  and 
sediment,  once  deposited,  is  periodical  removal  by  mechanical 
means  at  sufficiently  frequent  intervals  to  insure  against  injury  by 
too  great  accumulation.  Between  times,  some  good  may  be  done 
by  special  expedients  suited  to  the  individual  case.  No  one 
process  and  no  one  antidote  will  suffice  for  all  cases. 

"  Where  carbonate  of  lime  exists,  sal-ammoniac  may  be  used 
as  a  preventive  of  incrustation,  a  double  decomposition  occur- 
ring resulting  in  the  production  of  ammonia  carbonate  and 
calcium  chloride  —  both  of  which  are  soluble,  and  the  first  of 
which  is  volatile.  The  bicarbonate  may  be  in  part  precipitated 
before  use  by  heating  to  the  boiling  point,  and  thus  breaking 
up  the  salt  and  precipitating  the  insoluble  carbonate.  Solutions 
of  caustic  lime  and  metallic  zinc  act  in  the  same  manner. 
Waters  containing  tannic  acid  and  the  acid  juices  of  oak, 
sumach,  logwood,  hemlock,  and  other  woods,  are  sometimes 
employed,  but  are  apt  to  injure  the  iron  of  the  boiler,  as  may 
acetic  or  other  acid  contained  in  the  various  saccharine  matters 
often  introduced  into  the  boiler  to  prevent  scale,  and  which 
also  make  the  lime-sulphate  scale  more  troublesome  than  when 
clean.  Organic  matter  should  never  be  used. 

c  c  The  sulphate  scale  is  sometimes  attacked  by.  the  carbonate  of 
soda,  the  products  being  a  soluble  sodium  sulphate  and  a  pulver- 
ulent insoluble  calcium  carbonate,  which  settles  to  the  bottom  like 
other  sediments  and  is  easily  washed  off  the  heating  surfaces. 
Barium  chloride  acts  similarly,  producing  barium  sulphate  and 
calcium  chloride.  All  the  alkalies  are  used  at  times  to  reduce 
incrustations  of  calcium  sulphate,  as  is  pure  crude  petroleum,  the 
tannate  of  soda  and  other  chemicals. 

"  The  effect  of  incrustation  and  of  deposits  of  various  kinds,  is 
to  enormously  reduce  the  conducting  power  of  heating  surfaces ; 


684  HANDBOOK    ON    ENGINEERING. 

so  much  so,  that  the  power,  as  well  as  the  economic  efficiency  of 
a  boiler,  may  become  very  greatly  reduced  below  that  for  which  it 
is  rated,  and  the  supply  of  steam  furnished  by  it  may  become 
wholly  inadequate  to  the  requirements  of  the  case. 

"It  is  estimated  thaty1^  of  an  inch  (0.16  cm.)  thickness  of 
hard  scale  on  the  heating  surface  of  a  boiler  will  cause  a  waste 
of  nearly  one-eighth  of  its  efficiency,  and  the  waste  increases  as  the 
square  of  its  thickness.  The  boilers  of  steam  vessels  are 
peculiarly  liable  to  injury  from  this  cause  where  using  salt  water, 
and  the  introduction  of  the  surface  condenser  has  been  thus 
brought  about  as  a  remedy.  Land  boilers  are  subject  to  incrus- 
tation by  the  carbonate  and  other  salts  of  lime  and  by  the  deposit 
of  sand  or  mud  mechanically  suspended  in  the  feed  water. 

THE    TEMPERATURE    AND    PRESSURE    OF    SATURATED 

STEAM. 

The  accompanying  diagram  and  explanation,  taken  from  the 
technical  publication,  The  Locomotive,  will  be  found  much  more 
convenient  for  reference  than  steam  tables.  The  description  says 
that  one  of  the  most  fundamental  and  best  known  facts  in  steam 
engineering  is  that  saturated  steam  has  a  certain  definite  tem- 
perature for  each  and  every  definite  pressure ;  and  in  all  books 
on  steam  we  find  tables  of  corresponding  temperatures  and  pres- 
sures, by  the  use  of  which  we  are  enabled  to  find  out  what 
the  temperature  of  the  steam  is  when  we  know  what  the  pres- 
sure is,  and  vice  versa.  For  accurate  work  these  tables  are  all 
right ;  but  when  (as  is  usually  the  case)  we  do  not  need  to 
know  either  the  temperature  or  the  pressure  with  any  very 
great  precision,  a  diagram  which  presents  the  facts  directly  to 
the  eye  is  much  more  convenient.  Such  a  diagram  is  presented 
herewith.  On  the  left-hand  side  of  each  vertical  line  are 
marked  the  pressures,  and  on  the  right-hand  side  of  the  same 
lines  are  marked  the  corresponding  temperatures.  The  pres- 


50—- 
u*  - 


— 235' 


45 


40—1 


-  — 235*  -  — - 


35——2SO'        55— _ 


30 


—275* 
—270' 


25  —  1 


10 


Us 


HANDBOOK    ON    ENGINEERING. 
100— | 

'1*9       H 


685 


-230* 

SO- 


^-r260',  70-r 


15—  —  250         65— 


60 


^-210' 


-220' 


740— 


—  — ^       /25^ 


-J/5' 


-— J/0* 


115 


110  — 


705  — 


700  — 


/SO  — 


175— 


7^5  — 


— J45* 


—  J40* 


155— 


Us    ~ 


—  380' 


—37S* 


-370* 


3H,    Comparative    diagram    showing    the   temperature    and 
pressure  «f  saturated  steam. 


686  HANDBOOK    ON    ENGINEERING. 

sures  are  all  gauge  pressures,  that  is,  they  represent  the  direct 
gauge  reading  or  pressure  above  that  of  the  atmosphere.  The 
temperatures  are  on  the  Fahrenheit  scale.  The  diagram  is  based 
upon  Prof.  Cecil  H.  Peabody's  steam  tables,  it  is  therefore 
assumed  that  the  average  atmospheric  pressure  is  14.70  pounds 
per  square  inch. 

A  few  examples  will  make  the  use  of  the  diagram  clear:  (1) 
What  is  the  temperature  of  saturated  steam  when  it's  pressure, 
above  the  atmosphere,  is  75  pounds  per  square  inch?  Ans.  We 
find  75  pounds  on  the  left-hand  side  of  the  second  vertical  line, 
and  looking  on  the  other  side  of  the  line  we  see  that  the  corre- 
sponding temperature  is  just  a  fraction  of  a  degree  less  than  320 
degrees  Fahr.  (2)  What  is  the  temperature  of  saturated  steam 
when  its  pressure,  above  the  atmosphere,  is  197  Ibs.  per  square 
inch?  Ans.  We  find  197  Ibs.  on  the  left-hand  side  of  the  last 
vertical  line.  It  is  not  marked  in  figures,  but  195  is  so  marked, 
and  197  is  two  divisions  higher  than  195.  Looking  opposite  to 
197  we  see  that  the  corresponding  temperature  is  about  half  way 
between  386  degrees  and  387  degrees.  Hence,  we  conclude  that 
the  temperature  of  saturated  steam  at  the  given  pressure  is  about 
386^°.  (3)  When  the  temperature  of  saturated  steam  is  227°, 
what  is  its  pressure?  Ans.  We  find  227°  on  the  right-hand 
side  of  the  first  line,  two  divisions  above  225° ;  and  looking 
opposite  to  it,  we  see  that  the  gauge  pressure  corresponding  to 
this  temperature  is  almost  exactly  five  pounds.  (4)  When  the 
temperature  of  saturated  steam  is  363°,  what  is  its  pressure? 
Ans.  We  find  363°  on  the  right-hand  side  of  the  third  vertical 
line,  three  divisions  above  360°,  and  looking  on  the  other  side  of 
the  vertical  line,  we  see  that  the  corresponding  gauge  pressure  is 
about  144J  Ibs.  to  the  square  inch. 

SOMETHING   FOR  NOTHING. 

In  the  first  place,  it  should  be  remembered  that  in  mechanics 
the  measure  of  work  done  is  the  foot  pound,  a  term  which  defines 

' 


HANDBOOK  ON    ENGINEERING. 


68? 


itself.  A  foot  pound  of  work  is  the  amount  of  energy  required  to 
lift  one  pound  one  foot  high.  A  foot  pound,  therefore,  is  the 
product  of  force  and  distance,  force  being  simply  a  push  or  a 
pull.  A  machine  can  be  made  to  increase  the  acting  force,  as 
is  seen  in  the  case  of  a  crane,  where  the  weight  lifted  is  much 
greater  than  the  force  applied  at  the  handle  by  the  operator.  It 
is  also  possible  to  increase  the  distance  moved  by  some  part  of  a 
machine,  but  it  must  be  done  by  applying  a  greater  force  as  in 
the  case  of  a  steam  engine,  where  the  distance  moved  by  the  belt 
is  greater  than  the  space  passed  over  by  the  piston,  but  the  total 
pressure  of  the  steam  against  the  piston  is  greater  than  the 
effective  pull  exerted  by  the  belt. 


Melting  Points  of  Metals  and  Solids. 


Deg.  Fahr. 

Deg.  Fahr. 

Antimony 

melts  at 

....     951 

Platinum  melts  at 

....  4680 

Bismuth 

cc 

....     476 

Potassium 

tt 

....     136 

Brass 

tt 

....  1900 

Saltpeter 

te 

....     600 

Cadmium 

" 

....     602 

Steel 

tt 

.    2340  to  2520 

Cast  Iron 

ft 

.   1890  to  2160 

Sulphur 

(t 

....     225 

Copper 

ft 

....  1890 

Silver 

ft 

....   1250 

Glass 

tt 

....  2377 

Tin 

ft 

....     420 

Gold 

ft 

....  2250 

Wrought  Iron 

.  2700  to  2880 

Lead 

ft 

....     594 

Zinc 

ft 

....     740 

Ice 

tt 

....       32 

Aluminum 

ft 

....  1260 

In  both  the  crane  and  the  steam  engine,  however,  the  applied 
force  multiplied  by  the  distance  through  which  it  moves  in  a  given 
time,  must  be  enough  greater  than  the  product  of  the  force  at  the 
crane  hook  or  the  rim  of  the  fly-wheel,  and  the  distance  through 


688  HANDBOOK   ON    ENGINEERING. 

which  it  moves  to  make  up  for  the  loss  through  friction  in  the 
machine  itself.  The  foot  pounds  of  work  done  by  any  machine 
whatever  must  always  be  less  than  the  foot  pounds  put  into  the 
machine  in  the  same  length  of  time.  A  study  of  this  principle 
and  of  the  methods  of  applying  it,  is  all  that  is  necessary  to 
enable  one  to  decide  upon  the  soundness  of  the  claims  made  for 
any  power  multiplying  device.  A  British  Thermal  Unit  (B.  T. 
U.)  is  the  amount  of  heat  required  to  raise  the  temperature  of  a 
pound  of  water  1°  Fahr.,  and  its  dynamic  value  is  778  Ibs.  raised 
to  a  height  of  one  foot. 

CHIMNEYS. 

Chimneys  are  required  for  two  purposes:  1st,  to  carry  off 
obnoxious  gases  ;  2d,  to  produce  a  draft,  and  so  facilitate  com- 
bustion. The  first  requires  size,  the  second,  height.  Each  pound 
of  coal  burned  yields  from  13  to  30  pounds  of  gas,  the  volume  of 
which  varies  with  the  temperature.  The  weight  of  gas  to  be  car- 
ried off  by  a  chimney,  in  a  given  time,  depends  on  three  things  — 
size  of  chimney,  velocity  of  flow  and  density  of  gas.  But  as  the 
density  decreases  directly  as  the  absolute  temperature,  while  the 
velocity  increases  with  a  given  height,  nearly  as  the  square  root 
of  the  temperature,  it  follows  that  there  is  a  temperature  at  which 
the  weight  of  gas  delivered  is  a  maximum.  This  is  about  550° 
above  the  surrounding  air.  Temperature,  however,  makes  so 
little  difference  that  at  550°  above  the  quantity  is  only  4  per  cent 
greater  than  at  300°.  Therefore,  height  and  area  are  the  only 
elements  necessary  to  consider  in  an  ordinary  chimney.  The  in- 
tensity of  draft  is,  however,  independent  of  the  size,  and  depends 
upon  the  difference  in  weight  of  the  outside  and  inside  columns  of 
air,  which  varies  nearly  as  the  product  of  the  height  into  the 
difference  of  temperature.  This  is  usually  stated  in  an  equiva- 
lent column  of  water,  and  may  vary  from  0  to  possibly  2  inches. 
After  a  height  has  been  reached  to  produce  draft  of  sufficient 


HANDBOOK    ON    ENGINEERING. 


689 


Fig.  315.    Section  and  deration  cf  steel  stack. 


HANDBOOK    ON    ENGINEERING. 

intensity  to  burn  fine,  hard  coal,  provided  the  area  of  the  chimney 
is  large  enough,  there  seems  no  good  mechanical  reason  for  add- 
ing further  to  the  height,  whatever  the  size  of  the  chimney 
required.  Where  cost  is  no  consideration,  there  is  no  objection 
to  building  as  high  as  one  pleases  ;  but  for  the  purely  utilitarian 
purpose  of  steam  making,  equally  good  results  might  be  attained 
with  a  shorter  chimney  at  much  less  cost.  The  intensity  of  draft 
required  varies  with  the  kind  and  condition  of  the  fuel  and  the 
thickness  of  the  fires.  Wood  requires  the  least,  and  fine  coal  or 
slack  the  most.  To  burn  anthracite  slack  to  advantage,  a  draft 
of  1J  inch  of  water  is  necessary,  which  can  be  attained  by  a  well- 
proportioned  chimney  175  feet  high.  Generally,  a  much  less 
height  than  100  feet  cannot  be  recommended  for  a  boil!er,  as  the 
lower  grades  of  fuel  cannot  be  burned  as  they  should  be  with  a 
shorter  chimney. 

The  proportioning  of  chimneys  is  very  largely  a  matter  of  expe- 
rience and  judgment.  Various  rules  have  been  formulated  for 
this  purpose,  but  they  all  vary  more  or  less.  A  chimney  must 
have  sufficient  cross- section  to  easily  carry  off  the  products  of 
combustion,  and  be  high  enough  to  produce  sufficient  draft  for 
complete  and  rapid  combustion.  Where  there  is  a  choice  between 
a  high  narrow  stack  and  a  lower  wide  one,  the  nature  of  the  fuel 
should  decide  the  matter  ;  as  a  rule,  the  taller  stack  is  preferable. 
The  amount  of  fuel  to  be  burnt  per  square  foot  of  grate  per  hour 
has  been  increasing  in  modern  practice;  therefore,  the  old  rules  do 
not  fit  the  case  any  more.  Then  again,  it  makes  a  difference  how 
many  boilers  are  to  run  into  the  same  chimney.  The  heaviest 
work  of  the  chimney  is  immediately  after  firing,  since  the  friction 
through  the  fresh  coal  is  greater  and  the  temperature  less  then 
than  some  minutes  later.  But  it  would  be  bad  practice  to  fire  all 
boilers  or  all  doors  simultaneously.  Hence,  the  second  boiler 
does  not  require  as  much  area  as  the  first ;  say,  75  per  cent  will 
do.  After  that  there  comes  the  additional  consideration  that  as 


HANDBOOK   ON    ENGINEERING, 

rlM 


691 


Fig.  316.    Section  ami  elevation  of  brick  slack. 


692 


HANDBOOK    ON    ENGINEERING. 


the  diameter  of  the  stack  increases,  the  friction  in  stack  and 
breeching  decreases  rapidly.  Therefore,  for  the  third  and  each 
succeeding  boiler,  50  per  cent  of  the  first  area  will  suffice.  But 
as  more  are  added,  the  height  should  be  increased,  more  espe- 
cially if  the  horizontal  flue  from  boiler  to  stack  increases  in  length, 
as  it  usually  will.  A  good  rule  is  to  make  the  height  25  times 
the  diameter,  with  possibly  a  gradual  decrease  in  the  ratio  to  20 
times  the  diameter  for  the  larger  chimneys.  Thus  a  4-foot  diame- 
ter would  call  for  100  feet  height,  and  a  5-foot,  for  120  feet,  a 
6-foot  for  140  feet,  and  a  10-foot  for  200  feet  height. 


TABLE    OF    SIZES    OF    CHIMNEYS. 


«l 

ja 
3 

0> 

i 

Diameter  and  Nominal  Horse  Power. 

20" 

26" 

30" 

34" 

36" 

40" 

44" 

50" 

54" 

58" 

60" 

64" 

72" 

78" 

70  ft. 
80ft. 
90ft. 
100  ft. 
110ft. 
120  ft. 

40 

50 

60 
75 

100 
120 

130 
150 

150 
175 

175 

200 

200 
225 
250 

300 
340 
360 

375 
400 
425 

430 
455 
500 

500 
550 
600 

600 

650 
700 

750 
825 
900 

930 
990 
1050 

. 

I 

IRON   CHIMNEY   STACKS. 

In  many  places  iron  stacks  are  preferred  to  brick  chimneys. 
Iron  chimneys  are  bolted  down  to  the  base  so  as  to  require  no 
stays.  A  good  method  of  securing  such  bolts  to  the  stack  is 
shown  in  detail  in  the  figure  on  page  693.  Iron  stacks  require  to  be 
kept  well  painted  to  prevent  rust,  and  generally,  where  not  bolted 
down,  as  here  shown,  they  need  to  be  braced  by  rods  or  wires  to 
surrounding  objects.  With  four  such  braces  attached  to  an 
angle  iron  ring  at  f  the  height  of  stack,  and  spreading  laterally  at 


HANDBOOK    ON    ENGINEERING. 


693 


least  an  equal  distance,  each  brace  should  have  an  area  in  square 
inches  equal  to  y^1^  the  exposed  area  of  stack  (dia.  x  height)  in 
feet.  Stability  or  power  to  withstand  the  overturning  force  of 


Fig.  817.    Holding  down  bolts  and  lugs. 

the  highest  winds,  requires  a  proportionate  relation  between  the 
weight,  height,  breadth  of  base,  and  exposed  area  of  the  chimney. 
This  relation  is  expressed  in  the  equation 

dh* 

ri __  TIT" 

0     b          T' 

in  which  d  equals  the  average  breadth  of  the  shaft ;  k  =.  its 
height ;  b  =  the  breadth  of  base  —  all  in  feet ;  W  =  weight  of 
chimney  in  Ibs.,  and  C  =  a  coefficient  of  wind  pressure  per 


694 


HANDBOOK    ON    ENGINEERING. 


square  foot  of  area.  This  varies  with  the  cross-section  of  tbe 
chimney,  and  =  56  for  a  square,  35  for  an  octagon  and  28  for  a 
round  chimney.  Thus  a  square  chimney  of  average  breadth  of 
8  feet,  10  feet  wide  at  base  and  100  feet  high,  would  require  to 
weigh  56x8x100x10=448,000  Ibs.,  to  withstand  any  gale 
likely  to  be  experienced.  Brickwork  weighs  from  100  to  130 
Ibs.  per  cubic  foot;  hence,  such  a  chimney  must  average  13 
inches  thick  to  be  safe.  A  round  stack  could  weigh  half  as 
much,  or  have  less  base. 


WEIGHT      OF      SHEET      LAP      RIVETED      STEEL      SMOKE      STACKS, 
PER    FOOTo 

THICKNESS. 


DIJL. 

No. 

18 

No. 
16 

No. 
14 

NO. 

12 

No. 

10 

No. 

8 

A" 

aV 

i" 

A" 

A" 

ii" 

i" 

H" 

A" 

W 

V9 

12" 

8 

10 

13 

17 

21 

254 

314 

37 

42 

47 

524 

58 

63 

68i 

734 

78} 

84 

14" 

<-»i 

114 

15J 

20 

24* 

29} 

36} 

42 

484 

544 

62i 

67 

734 

79i 

85 

91 

97 

16" 

10* 

13 

174 

23 

28 

34 

42 

49 

56 

63 

70 

77 

84 

91 

98 

105 

112 

18" 

Hi 

14i 

26 

31| 

47 

55 

63 

71 

79 

86 

94 

102 

110 

118 

126 

20" 

13 

16 

22 

2^} 

35* 

42* 

52 

60 

69 

78 

86 

95 

104 

113 

121 

131 

138 

22" 
24" 

14* 

154 

HI 

19* 

24J 

264 

3lf 
34i 

38| 
42 

51 

54 
59 

63| 

73 

784 

82 
88 

91 
98 

99 

108 

108 
118 

118 
128 

127 
137 

137 
147 

146 
157 

26" 

16| 

21 

28} 

37 

454 

63 

734 

84 

94 

105 

115 

126 

137 

147 

158 

168 

28" 

18 

31 

40 

49 

694 

67 

78 

89* 

100 

111 

122 

134 

145 

156 

167 

179 

80" 

244 

33 

42} 

52| 

71 

83 

95" 

1064 

118 

130 

142 

154 

166 

178 

190 

32" 

35 

45i 

56 

68 

75 

874 

1004 

113 

125 

138 

150 

163 

175 

188 

201 

34" 

28 

37 

48; 

594 

72J 

80 

93 

106 

119 

132 

146 

160 

173 

186 

199 

212 

36" 

39 

51 

63 

76J 

85 

100 

114 

128 

143 

158 

173 

188 

202 

216 

230 

38" 

3lf 

41* 

53| 

664 

90 

105 

120 

135 

151 

166 

182 

198 

213 

227 

242 

40" 

33| 

43* 

68 

70 

85 

94 

110 

126 

142 

158 

174 

191 

208 

224 

239 

254 

42" 

35 

45} 

59J 

734 

89* 

98 

115 

132 

149 

166 

183 

200 

217 

234 

260 

266 

44" 

36} 

48 

62 

77 

934 

103 

121 

138 

155 

173 

191 

209 

227 

245 

262 

279 

4«" 

65 

804 

97} 

107 

126 

144 

162 

181 

199 

218 

237 

255 

273 

291 

48" 

40 

524 

68 

84 

102 

112 

131 

150 

169 

188 

208 

227 

247 

266 

284 

303 

60" 
52" 
64" 

54} 
57 

71 
74 

77 

874 
91 
944 

106J 
1104 
114} 

116 
121 
124 

136 
142 
147 

156 
162 
168 

176 
182 
189 

195 
203 
211 

216 
224 
233 

236 
245 
254 

258 
266 
276 

277 

287 
298 

296 
307 
319 

315 
328 
349 

68" 

80 

98* 

119* 

133 

158 

180 

202 

225 

248 

270 

294 

317 

340 

363 

58" 

83 

102 

123* 

137 

164 

186 

209 

232 

256 

280 

304 

327 

351 

375 

60" 

86 

106 

127* 

142 

169 

192 

215 

240 

264 

289 

314 

338 

362 

387 

62" 

89 

110 

131} 

146 

174 

198 

222 

247 

273 

298 

324 

349 

374 

400 

6i" 

.... 

92 

114 

136 

151 

179 

204 

229 

255 

281 

307 

333 

359 

885 

412 

HANDBOOK   ON   ENGINEERING.  695 

CHAPTER    XXIV. 
HORSE=POWER  OF  GEARS. 

To  determine  the  horse-power,  which  any  gear-wheel  will  trans- 
mit, four  facts  are  required  to  be  known :  — 

1st.  The  kind  of  wheel,  whether  spur,  bevel,  spur  mortise,  or 
bevel  mortise.  2d.  The  pitch.  3d.  The  face.  4th.  The  velocity 
of  pitch  circle  in  feet  per  second. 

Generally,  the  fourth  fact  is  not  known.  It  can  be  found  if 
the  pitch  diameter  of  the  wheel  in  inches  and  the  number  of  revo- 
lutions per  minute  are  given,  for  it  can  be  obtained  from  them  by 
the  following  rule :  — 

Rule,  —  Given  the  pitch  diameter  in  inches  and  the  number  of 
revolutions  per  minute ;  to  find  the  velocity  of  pitch  line  in  feet 
per  second. 

First,  multiply  the  pitch  diameter  (in  inches)  by  the  number 
of  revolutions  per  minute.  Second,  divide  the  product  thus  found 
by  230.  The  quotient  is  the  velocity  required. 

Example. — What  is  the  velocity  of  the  pitch  circle  of  a 
gear-wheel  in  feet  per  second,  the  pitch  diameter  =  43  inches, 
the  revolutions  per  minute  =125? 

43  x  125  divided  by  230  =  23.4  feet  per  second. 

Table  A  shows  the  greatest  horse-power,  which  different  kinds 
of  gears  of  1-inch  pitch  and  1-inch  face  will  safely  transmit  at 
various  pitch-line  velocities.  To  find  the  greatest  horse-power 
which  any  other  pitch  and  face  will  safely  transmit,  the  following 
rule  can  be  used :  — 

Rule* —  Given,  the  pitch  (in  inches),  face  (in  inches),  velocity 
of  pitch  circle  (in  feet  per  second),  and  kind  of  gear ;  to  find  the 
greatest  horse-power  that  can  be  safely  transmitted. 

First.  Find  the  horse-power  in  Table  A,  which  the  given  kind 


696 


HANDBOOK    ON     ENGINEERING. 


of  wheel  with  1-inch  pitch  and  1-inch  face  will  transmit  at  the 
given  velocity.  Second.  Multiply  the  pitch  by  the  face.  Third. 
Multiply  the  horse-power  found  by  the  product  of  pitch  by  face. 
The  final  product  is  the  horse-power  required. 

Example.  —  What  is  the  greatest  horse-power  that  a  bevel- 
wheel,  43"  pitch  diameter,  2"  pitch,  6"  face,  and  125  revolutions 
per  minute  will  safely  transmit? 

From  previous  example,  we  have  found  the  pitch-line  velocity 
to  be  23.4  feet  per  second,  which  is  nearest  to  a  velocity  of  24 
feet  per  second  in  Table  A. 

First,  the  horse-power  which  a  bevel  wheel  of  1"  pitch  and  1' 
face  will  transmit  is  (from  table)  at  this  velocity  4.931. 

Second,  the  product  of  pitch  by  face  is  2x6  =  12. 

Third,  12x4.931  —59.17  horse-power.     Answer. 

Whenever  it  is  desirable  to  know  about  the  average  horse- 
power that  any  wheel  will  transmit,  f  or  |  of  the  results  obtained 
by  the  rule  above  should  be  taken. 


TABLE  A. — TABLE  SHOWING  THE  HORSE-POWER  WHICH  DIFFERENT 
KINDS  OF  GEAR  WHEELS  OF  ONE  INCH  PITCH  AND  ONE  INCH  FACE 
WILL  TRANSMIT  AT  VARIOUS  VELOCITIES  OF  PITCH  CIRCLE. 


1 

2 

3 

4 

5 

Velocity  of 
pitch  circle  in 
ft.  per  sec. 

Spur  Wheels. 

Spur  Mortise 
Wheels. 

Bevel  Wheels. 

Bevel 
Mortise 
Wheels. 

2 

1.338 

.647 

.938 

.647 

3 

1.756 

.971 

1.227 

.856 

6 

2.782 

1.76 

1.76 

1  363 

12 

4.43 

3.1 

3.1 

2.16 

18 

5.793 

4.058 

4.058 

2.847 

24 

7.052 

4.931 

4.931 

3.447 

30 

8.182 

5.727 

5.727 

4.036 

36 

9.163 

6.314 

6.414 

4.516 

42 

10.156 

7.102 

7.102 

4963 

48 

10.683 

7.680 

7.680 

5.411 

HANDBOOK    ON    ENGINEERING. 


697 


NOTE.  —  When  velocities  are  given,  which  are  between  those 
in  table,  the  horse-power  can  be  found  by  interpolation. 

Thus,  the  horse-power  for  spur  wheels  at  14  feet  velocity  is 
found  as  follows :  — 


14  minus  12  =  ! 
18       "      12  =  ( 


5.793  minus  4.43=  1.363. 


Then  £  of  1.363  ==  .454  and  .454  +  4.43  =  4. 884  horse-power. 

TABLE  B.  — SHAFTING.  — HORSE- POWER  TRANSMITTED  BY  VARIOUS 
SHAFTS,  AT  100  REVOLUTIONS  PER  MINUTE  UNDER  VARIOUS  CON- 
DITIONS. 


1 

2 

3 

4 

1 

2 

3 

4 

Shafts 

Shafts 

Diameter 
of  Shaft. 

Line 
Shafts. 

Shaft  as 
.  a  Prime 
Mover. 

Under 
Slight 
Bending 

Diameter 
of  Shaft. 

Line 

Shafts. 

Shaft  as 
a  Prime 
Mover. 

Under 
Slight 
Bending 

Strain. 

Strain. 

1H' 

.7 

.4 

1.3 

*w 

40. 

20. 

80 

1.3 

.7 

2.6 

3if" 

49. 

25. 

97- 

1-Jg.' 

2.4 

1.2 

4.7 

^tV 

70. 

35. 

139. 

jll' 

3.8 

1.9 

7.6 

4i|' 

96. 

48. 

192. 

itf 

5.8 

2.9 

11.5 

5-V 

126. 

64. 

256. 

2iV 

8.3 

4.2 

16.6 

45* 

167. 

84. 

334. 

2ft; 

11.5 
15.5 

5.8 
7.8 

23. 
31. 

1 

266. 
399. 

133. 

200. 

532. 
797. 

2^' 

20. 

10. 

40. 

8||; 

570. 

285. 

1139. 

8iV 

26. 

13. 

51. 

783. 

.392. 

•I  566. 

3&" 

33. 

17. 

65. 

This  table  gives  the  horse-power  that  various  sizes  of  shafts 
will  safely  transmit  at  100  revolutions  per  minute  under  various 
conditions. 

Prime  movers  are  those  shafts  in  which  the  variation  above 
and  below  the  average  horse-power  transmitted  is  great,  also 
where  the  transverse  strain  due  to  belts  or  heavy  pulleys  is  large, 
such  as  jack-shafts,  crank-shafts,  etc. 


698  HANDBOOK    ON    ENGINEERING. 


WHEEL  GEARING. 

The  pitch  line  of  a  wheel  is  the  circle  upon  which  the  pitch 
is  measured,  and  it  is  the  circumference  by  which  the  diameter, 
or  the  velocity  of  the  wheel,  is  measured.  The  pitch  is  the  arc 
of  the  circle  of  the  pitch  line,  and  is  determined  by  the  num- 
ber of  teeth  in  the  wheel.  The  true  pitch  (chordal),  or  that 
by  which  the  dimensions  of  the  tooth  of  a  wheel  are  alone 
determined,  is  a  straight  line  drawn  from  the  centers  of  two 
contiguous  teeth  upon  the  pitch  line.  The  line  of  centers  is 
the  line  between  the  centers  of  two  wheels.  The  radius  of  a 
wheel  is  the  semi-diameter  running  to  the  periphery  of  a  tooth. 
The  pitch  radius  is  the  semi-diameter  running  to  the  pitch  line. 
The  length  of  a  tooth  is  the  distance  from  its  base  to  its  ex- 
tremity. The  breadth  of  a  tooth  is  the  length  of  the  face  of 
wheel.  The  teeth  of  wheels  should  be  as  small  and  numerous 
as  is  consistent  with  strength.  When  a  pinion  is  driven  by 
a  wheel,  the  number  of  teeth  in  the  pinion  should  not  be 
less  than  eight.  When  a  wheel  is  driven  by  a  pinion,  the 
number  of  teeth  in  the  pinion  should  not  be  less  than  ten. 
The  number  of  teeth  in  a  wheel  should  always  be  prime  to  the 
number  of  the  pinion ;  that  is,  the  number  of  teeth  in  the 
wheel  should  not  be  divisible  by  the  number  of  teeth  in  the 
pinion,  without  a  remainder.  This  is  in  order  to  prevent  the 
same  teeth  coming  together  so  often  as  to  cause  an  irregular 
wear  of  their  faces.  An  odd  tooth  introduced  into  a  wheel  is 
termed  a  hunting-tooth  or  cog. 

TO    COMPUTE    THE    PITCH    OF    A    WHEEL. 

Rule*  —  Divide  the  circumference  at  the  pitch-line  by  the  num- 
ber of  teeth. 

Example.  —  Awheel  40  in.  in  diameter,  requires  75  teeth; 
what  is  its  pitch  ? 

3.1416  x40= 


HANDBOOK    ON    ENGINEERING.  699 

TO    COMPUTE    THE     CHORDAL    PITCH. 

—  Divide  180°  by  tHe  number  of  teeth,  ascertain  the  sin. 
of  the  quotient,  and  multiply  it  by  the  diameter  of  the  wheel. 

Example. — The  number  of  teeth  is   75  and  the   diameter  40 
in. ;  what  is  the  true  pitch  ? 

i^_  =  2°  24'  and  sin.  of  2°  24'  =  .04188,  which  x  40  =  1.6752  in. 

TO  COMPUTE  THE  DIAMETER  OF  A  WHEEL. 

Rule*  —  Multiply  the  number  of  teeth  by  the  pitch,  and  divide 
the  product  by  3. 1416. 

Example. — The  number   of   teeth  in   awheel  is  75,  and  the 
pitch  1.675  in. ;  what  is  the  diameter  of  it? 
75x1.675 


3.1416 


=  40  in. 


TO    COMPUTE    THE    NUMBER    OF    TEETH    IN    A    WHEEL. 

Rule*  —  Divide  the  circumference  by  the  pitch. 

TO  COMPUTE  THE    DIAMETER    WHEN  THE    TRUE  PITCH    IS    GIVEN. 

Rule*  —  Multiply  the  number  of  teeth  in  the  wheel  by  the  true 
pitch,  and  again  by  .3184. 

Example.  —  Take  the  elements  of  the  preceding  case. 
75  x  1.6752  x  .3184  ==  40  in. 

TO  COMPUTE    THE    NUMBER    OF  TEETH  IN  A    PINION    OR    FOLLOWER  TO 
HAVE    A    GIVEN    VELOCITY. 

Rule*  —  Multiply  the  velocity  of  the  driver  by  its  number  of 
teeth,  and  divide  the  product  by  the  velocity  of  the  driven. 

Example.  —  The  velocity  of  a  driver  is  16  revolutions,  the 
number  of  its  teeth  54,  and  the  velocity  of  the  pinion  is  48  ;  what 
is  the  number  of  its  teeth  ? 


=  18  teeth. 
48 


700  HANDBOOK    ON    ENGINEERING. 

2.  A  wheel  having  75  teeth  is  making  16  revolutions  per  min- 
ute.    What  is  the  number  of  teeth  required  in  the  pinion  to  make 
24  revolutions  in  the  same  time? 
16  x  75 


24 


=  50  teeth. 


TO    COMPUTE    THE    PROPORTIONAL    RADIUS  OF    A     WHEEL    OR  PINION. 

Rule* —  Multiply  the  length  of  the  line  of  centers  by  the  num- 
ber of  teeth  in  the  wheel  for  the  wheel,  and  in  the  pinion  for  the 
pinion,  and  divide  by  the  number  of  teeth  in  both  the  wheel  and 
the  pinion. 

TO  COMPUTE  THE  DIAMETER  OF  A  PINION,  WHEN  THE  DIAMETER  OF 
THE  WHEEL  AND  NUMBER  OF  TEETH  IN  THE  WHEEL  AND  PINION 
ARE  GIVEN. 

Rule*  —  Multiply  the  diameter  of  the  wheel  by  the  number  of 
teeth  in  the  pinion,  and  divide  the  product  by  the  number  of  teeth 
in  the  wheel. 

Example. — The  diameter  of  a  wheel  is  25  in.,  the  number  of 
its  teeth  210,  and  the  number  of  teeth  in  the  pinion  30  ;  what  is 
the  diameter  of  the  pinion  ? 

25x30 


210 


=  3.57  in. 


TO  COMPUTE  THE    CIRCUMFERENCE    OF  A  WHEEL. 

Rule*  —  Multiply  the  number  of  teeth  by  their  pitch. 

TO  COMPUTE  THE  REVOLUTIONS  OF   A  WHEEL  OR  PINION. 

Rule*  —  Multiply  the  diameter  or  circumference  of  the  wheel  or 
the  number  of  its  teeth,  as  the  case  may  be,  by  the  number  of  its 
revolutions,  and  divide  the  product  by  the  diameter,  circumfer- 
ence, or  number  of  teeth  in  the  pinion. 

Example.  —  A  pinion  10  in.  in  diameter  is  driven  by  a  wheel 


HANDBOOK    ON    ENGINEERING.   .  701 

2  ft.  in  diameter,  making  46  revolutions  per  minute ;  what  is  the 
number  of  revolutions  of  the  pinion  ? 
2  x  12  x  46 


10 


=  110.4  revolutions. 


TO    COMPUTE    THE    RELATIVE    VELOCITY    OF    A    PINION. 

Rule*  —  Divide  the  diameter,  circumference  or  number  of  teeth 
in  the  driver,  as  the  case  may  be.  by  the  diameter,  etc.,  of  the 
pinion. 

WHEN  THERE  IS  A  SERIES  OR  TRAIN  OF  WHEELS  AND  PINIONS. 

Rule*  —  Divide  the  continued  product  of  the  diameter,  circum- 
ference, or  number  of  teeth  in  the  wheels  by  the  continued 
product  of  the  diameter,  etc.,  of  the  pinions. 

Example.  — If  a  wheel  of  32  teeth  drive  a  pinion  of  10,  upon 
the  axis  of  which  there  is  one  of  30  teeth,  driving  a  pinion  of  8? 
what  are  the  revolutions  of  the  last? 

32     30       960 

77,  x  —  =  -57-  =12  revolutions. 

1U        o  oU 

Ex.  2.  — The  diameters  of  a  train  of  wheels  are  6,  9,  9,  10  and 
12  in. ;  of  the  pinions,  6,  6,  6,  6,  and  6  in.  ;  and  the  number  of 
revolutions  of  the  driving  shaft  or  prime  mover  is  10 ;  what  are 
the  revolutions  of  the  last  pinion  ? 

6  x  9  x  9  x  10  x  12  x  10       583200 

= ==_  75  revolutions. 

6x6x6x6x6  7776 

TO  COMPUTE  THE  PROPORTION  THAT  THE  VELOCITIES  OF  THE  WHEELS 
IN  A  TRAIN  WOULD  BEAR  TO  ONE  ANOTHER. 

Rule*  —  Subtract  the  less  velocity  from  the  greater,  and  divide 
the  remainder  by  one  less  than  the  number  of  wheels  in  the  train ; 
the  quotient  is  the  number,  rising  in  arithmetical  progression  from 
the  less  to  the  greater  velocity. 


702  HANDBOOK    ON    ENGINEERING. 

Example.  —  What  should  be  the  velocities  of  three  wheels  to 
produce  18  revolutions,  the  driver  making  3  ? 

18  minus  3  =  15        _  K 

—  =  7.5  =  number  to  be  added  to  velocity  of  the 
3  minus  1=2 

iriver  =  7.5  +  3  =  10.5     and    10.5  +  7.5  =  18    revolutions. 
Hence,  3,  10.5  and  18  are  the  velocities  of  the  three  wheels. 

GENERAL   ILLUSTRATIONS. 

1.  A  wheel  96  inches   in  diameter,  making  42  revolutions  per 
minute,  is  to  drive  a  shaft  75  revolutions  per  minute,  what  should 
be  the  diameter  of  the  pinion  ? 

96x42 

=53.76  m. 

75 

2.  If  a  pinion  is  to  make  20  revolutions  per  minute,  required 
the  diameter  of  another  to  make  58  revolutions  in  the  same  time. 
58  divided  by  20  =  2.9  =  the  ratio  of  their  diameters.     Hence 
if  one  to  make  20   revolutions  is  given  a  diameter  of  30  in.,  the 
other  will  be  30  divided  by  2.9  =  10.345  in. 

3.  Required  the  diameter  of  a  pinion  to  make  12  J  revolutions 
in  the  same  time  as  one  of  32  in.  diameter  making  26. 

32x26          „  -„  . 

66.56  in. 

12.5 

4.  A  shaft  making  22  revolutions  per  minute,  is  to  drive  another 
shaft  at  the  rate  of  15,  the  distance  between  the  two  shafts  upon 
the  line  of  centers  is  45  in.  ;  what  should  be  the  diameter  of  the 
wheels  ? 

Then,  1st,  22  +  15  :  22  :  :  45  :  26.75  =  inches  in  the  radius  of 
the  pinion. 

2d.  22  +  15  :  15  : :  45  :  18.24  =  inches  in  the  radius  of  the  spur. 

5.  A  driving  shaft,  making  16    revolutions   per  minute,  is  to 
drive  a  shaft  81  revolutions  per  minute,  the  motion  to  be   com- 
municated by  two  geared  wheels  and  two  pulleys,  with   an  inter- 
mediate shaft ;  the  driving  wheel  is  to  contain  54  teeth,  and  the 


HANDBOOK    ON    ENGINEERING.  703 

driving  pulley  upon  the  driven  shaft  is  to  be  25  in.  in  diameter ; 
required  the  number  of  teeth  in  the  driven  wheel,  and  the  diameter 
of  the  driven  pulley.  Let  the  driven  wheel  have  a  velocity  of 
V  16x81=36  a  mean  proportional  between  the  extreme  veloci- 
ties 16  and  81. 

Then,  1st,  36  :  16  :  :  54  :  24  =  teeth  in  the  driven  wheel. 

2d.  81:  36::  25:  11. 11=  inches  diameter  of  the  driven  pulley. 

6.  If ,  as  in  the  preceding  case,  the  whole  number  of  revolutions 
of  the  driving  shaft,  the  number  of  teeth  in  its  wheel  and  the 
diameter  of  the  pulley  are  given,  what  are  the  revolutions  of  the 
shafts  ? 

Then,  1st,  18  :  16  : :  54  :  48  =  revolutions  of  the  intermediate 
shaft. 

2d.   15  :  48  :  :  25  :  80  =  revolutions  of  the  driven  shaft. 

TO    COMPUTE  THE    DIAMETER  OF    A  WHEEL  FOR  A  GIVEN    PITCH    AND 
NUMBER  OF  TEETH. 

Rale*  —  Multiply  the  diameter  in  the  following  table  for  the 
number  of  teeth  by  the  pitch,  and  the  product  will  give  the  diam- 
eter at  the  pitch  circle. 

Example. — What  is  the  diameter  of  a  wheel  to  contain  48 
teeth  of  2.5  in.  pitch? 

15.29x2.5  =  38.225  in. 

TO  COMPUTE    THE    PITCH    OF  A    WHEEL    FOR  A    GIVEN  DIAMETER    AND 
NUMBER    OF    TEETH. 

Rule*  —  Divide  the  diameter  of  the  wheel  by  the  diameter  in 
the  table  for  the  number  of  teeth,  and  the  quotient  will  give  the 
pitch. 

Example.  —  What  is  the  pitch  of  a  wheel  when  the  diameter  of 
it  is  50.94  in.,  and  the  number  of  its  teeth  80? 

50.94 

. 9  ,„ 

25.47  -^ln- 


704 


HANDBOOK    ON    ENGINEERING. 


PITCH  OF  WHEELS. 

A   TABLE   WHEREBY   TO    COMPUTE    THE    DIAMETER   OF   A   WHEEL   FOR  A 
GIVEN    PITCH,    OR   THE    PITCH   FOR   A   GIVEN    DIAMETER. 

From  8  to  192  teeth. 


S 

03 

,c 

| 

j 

03 

^ 

£ 

a 

g 

«M  03 

03 

•nt; 

03 

<M  03 

"03 

**  03 

03 

s-  03 

"S 

•H 

g 

cs 

0  0) 

I 

0  03 

I 

0  03 

g 

003 

B 

z; 

5 

5z 

5 

& 

5 

fc 

S 

& 

5 

8 

2.61 

45 

14.33 

82 

26.11 

119 

37.88 

156 

49.66 

9 

2.93 

46 

14.65 

83 

26.43 

120 

38.2 

167 

49.98 

10 

3.24 

47 

14.97 

84 

26.74 

121 

38.52 

158 

50.3 

11 

3.55 

48 

15.29 

85 

27.06 

122 

38.84 

159 

50-61 

12 

3.86 

49 

16.61 

86 

27.38 

123 

39.16 

160 

50.93 

13 

4.18 

50 

15.93 

87 

27.7 

124 

39.47 

161 

51.25 

14 

4.49 

51 

16.24 

88 

28.02 

125 

39.79 

162 

51.57 

15 

4.81 

52 

16.66 

89 

28.33 

126 

40.11 

163 

51.89 

16 

5.12 

53 

16.88 

90 

28.65 

127 

40.43 

164 

52.21 

17 

5.44 

54 

17.2 

91 

28.97 

128 

40.75 

165 

52.52 

18 

5.76 

55 

17.52 

92 

29.29 

129 

41.07 

166 

52.84 

19 

6.07 

56 

17.8 

93 

29.61 

130 

41.38 

167 

53.16 

20 

6.39 

57 

18.15 

94 

29.93 

131 

41.7 

168 

53.48 

21 

6.71 

58 

18.47 

95 

30.24 

132 

42.02 

169 

53.8 

22 

7.03 

59 

18.79 

9« 

30.56 

133 

42.34 

170 

54.12 

23 

7.34 

60 

19.11 

97 

30.88 

134 

42.66 

171 

54.43 

24 

7.66 

61 

19.42 

98 

31.2 

135 

42.98 

172 

54.75 

25 

7.98 

62 

19.74 

99 

31.52 

136 

43.29 

173 

55.07 

26 

8.3 

63 

20.06 

100 

31.84 

137 

43.61 

174 

55.39 

27 

8.61 

64 

20.38 

101 

32.15 

138 

43.93 

175 

55.71 

28 

8.93 

65 

20.7 

102 

32.47 

139 

44.25 

176 

56.02 

29 

9.25 

66 

21.02 

103 

32.79 

140 

44.57 

177 

56.34 

30 

9.57 

67 

21.33 

104 

33.11 

141 

44.88 

178 

56.66 

31 

9.88 

68 

21.65 

105 

33.43 

142 

45.2 

179 

56.98 

32 

10.2 

69 

21.97 

106 

33.74 

143 

45.52 

180 

57.23 

33 

10.52 

70 

22.29 

107 

34.06 

144 

45.84 

181 

57.62 

34 

10.84 

71 

22.61 

108 

34.38 

145 

46.16 

182 

57.93 

35 

11.16 

72 

22.92 

109 

34.7 

146 

46.48 

183 

58.25 

36 

11.47 

73 

23.24 

110 

35.02 

147 

46.79 

184 

58.57 

37 

11.79 

74 

23.56 

111 

35.34 

148 

47.11 

185 

58.89 

38 

12.11 

75 

23.88 

112 

35.65 

149 

47.43 

186 

59.21 

39 

12.43 

76 

24.2 

113 

35.97 

150 

47.75 

187 

59.53 

40 

12.74 

77 

24.52 

114 

36.29 

151 

48.07 

188 

59.84 

41 

13.06 

78 

24.83 

115 

36.61 

152 

48.39 

189 

60.16 

42 

13.38 

79 

25.15 

116 

36.93 

163 

48.7 

190 

60.48 

43 

13.7 

80 

25.47 

117 

37.25 

154 

49.02 

191 

60.81 

44 

14.02 

81 

25.79 

118 

37.66 

155 

49.34 

192 

61.13 

HANDBOOK    ON   ENGINEERING. 
TO    COMPUTE    THE    STRESS    THAT    MAY    BE    BORNE    BY    A  TOOTH. 

Rule*  —  Multiply  the  value' of  the  material  of  the  tooth  to  re- 
sist transverse  strain,  as  estimated  for  this  character  of  stress,  by 
the  breadth  and  square  of  its  depth,  and  divide  the  product  by 
the  extreme  length  of  it  in  the  decimal  of  a  foot. 

TO    COMPUTE    THE    NUMBER    OF    TEETH     OF    A    WHEEL    FOR    A    GIVEN 
DIAMETER    AND    PITCH. 

Rule*  —  Divide  the  diameter  by  the  pitch,  and  opposite  to  the 
quotient  in  the  preceding  table  is  given  the  number  of  teeth. 

TEETH  OF  WHEELS. 

Epicycloidal*  —  In  order  that  the  teeth  of  the  wheels  and  pin- 
ions should  work  evenly  and  without  unnecessary  rubbing  fric- 
tion, the  face  (from  pitch  line  to  top)  of  the  outline  should  be 
determined  by  an  epicycloidal  curve,  and  the  flank  (from  pitch 
line  to  base)  by  an  hypocycloidal.  When  the  generating  circle  is 
equal  to  half  the  diameter  of  the  pitch  circle,  the  hypocycloid  de- 
scribed by  it  is  a  straight  diametrical  line,  and  consequently  the 
outline  of  a  flank  is  a  right  line  and  radial  to  the  center  of  the 
wheel.  If  a  like  generating  circle  is  used  to  describe  face  of  a 
tooth  of  other  wheel  or  pinion  respectively,  the  wheel  and  pinion 
will  operate  evenly. 

Involute*  —  Teeth  of  two  wheels  will  work  truly  together  when 
surfaces  of  their  face  is  an  involute ;  and  that  two  such  wheels 
should  work  truly,  the  circles  from  which  the  involute  lines  for 
each  wheel  are  generated  must  be  concentric  with  the  wheels, 
with  diameters  in  the  same  ratio  as  those  of  the  wheels. 

Curves  of  teeth*  —  In  the  pattern  shop,  the  curves  of  epicy- 
cloidal or  involute  teeth  are  defined  by  rolling  a  template  of  the 
generating  circle  on  a  template  corresponding  to  the  pitch  line, 

a  scriber  on  the  periphery  of  the  template  being  used   to  define 

45 


70b 


HANDBOOK    ON    ENGINEERING. 


the  curve.  Least  number  of  teeth  that  can  be  employed  in  pin- 
ions having  teeth  of  following  classes,  are:  involute,  25; 
epicycloidal,  12  ;  staves  or  pins,  6. 


CONSTRUCTION  OF  GEARING. 

If  the  dimensions  of  two  wheels  are  determined,  as  well  as 
the  size  of  the  teeth  and  spaces,  the  wheel  is  drawn  as  shown 
in  figure.  The  star  ting- 
point  for  the  division  of 
the  wheels  is  where  the 
two  pitch  circles  meet 
in  A.  It  is  advisable 
to  determine  the  exact 
diameters  of  the  wheels 
by  calculation,  if  the 
difference  between 
them  is  remarkable  ;  for 
any  division  upon  two 
circles  of  unequal  size 

by  means  of  a  divider,  jolg.  313.  involute  gear  teeth. 
is  incorrect,  because  the  latter  measures  the  chord  instead  of  the 
arc.  From  the  point  A  we  construct  the  epicycloid  (7,  by  rolling 
the  circle  A  upon  5,  as  its  base  line.  That  short  piece  of  the  epi- 
cycloid, from  the  pitch  line  to  the  face  of  the  tooth,  is  the  curva- 
ture for  that  part  of  the  tooth  and  the  wheel  B.  This  curvature 
obtained  for  one  side  of  the  tooth,  serves  for  both  sides  of  it,  and 
also  for  all  the  teeth  in  the  wheel.  The  lower  part  of  the  tooth, 
or  that  inside  the  pitch -line,  is  immaterial  to  the  working  of  the 
wheel ;  this  may  be  a  straight  line,  as  shown  by  the  dotted  lines 
which  are  in  the  direction  of  the  diameters,  or  may  be  a  curved 
line,  as  is  seen  in  the  wheel  A.  This  line  must  be  so  formed  as 
not  to  touch  the  upper  or  curved  part  of  the  tooth.  The  root  of 


\ 


HANDBOOK    ON    ENGINEERING. 


707 


the  tooth,  or  that  part  of  it  which  is  connected  with  the  rim  of  the 
wheel,  is  the  weakest  part  of  the  tooth,  and  may  be  strengthened 
by  filling  the  angles  at  the  corners.  The  curvature  for  the  teeth 
in  the  wheel  A  is  found  in  a  similar  manner  to  that  of  B.  The 
pitch  circle  A  serves  now  as  a  base  line,  and  the  circle  B  is  rolled 
upon  it,  to  obtain  the  circle  D.  This  line  forms  the  curvature  for 
the  teeth  of  A,  and  serves  for  all  the  teeth  in  A  —  also  for  both 
sides  of  the  teeth.  In  most  practical  cases  the  curvature  of  the 
teeth  is  described  as  a. part  of  a  circle,  drawn  from  the  center  of 
the  next  tooth,  or  from  a  point  more  or  less  above  or  below  that 
center,  or  the  radius  greater  or  less  in  strength  than  the  pitch  of 
the  wheel.  Such  circles  are  never  correct  curves,  and  no  rule  can 
be  established  by  which  their  size  and  center  meets  the  form  of 
the  epicycloid. 

BEVEL    WHEELS. 

If  the  lines  C  A  and  B  C  represent  the  prolonged  axes,  which 
are  to  revolve  with  different  or  similar  velocities,  the  position  and 

sizes  of  the  wheels  for 
driving  these  axes  are 
determined  by  the  dis- 
tance of  the  wheels  from 
the  point  C.  The  diame- 
ters of  the. wheels  are  as 
the  angles  a  and  b  and 
inversely  as  the  number 
of  revolutions.  These 
angles  are,  therefore,  to 
be  determined  before  the 

319.    Bevel  gears.  wheels    can    be    drawn. 

By  measuring  the  distances  from  C  to  the  line  E,  or  from  C  to 
F,  the  sizes  of  the  wheels  are  determined.  These  lines  E,  F  and 
D  F,  are  the  diameters  for  the  pitch  lines ;  from  them  the  form 


708 


HANDBOOK    ON    ENGINEERING 


of  the  tooth  is  described  on  the  beveled  face  of  the  wheel.  If 
the  form  of  the  tooth  is  described  on  the  largest  circle  of  the 
wheel,  all  the  lines  from  this  face  run  to  the  point  (7,  so  that  when 
the  wheel  revolves  around  its  axis,  all  the  lines  from  the  teeth 
concentrate  in  the  point  (7,  and  form  a  perfect  cone.  Curvature, 
thickness,  length  and  spaces  are  here  calculated  as  on  face 
wheels ;  the  thickness  is  measured  in  the  middle  of  the  width  of 
the  wheel. 

WORM-SCREW. 

If  a  single  screw  A  works  in  a  toothed  wheel,  each  revolution 
of  the  screw  will  turn  the  wheel  one  cog  ;  if  the  screw  is  formed 
of  more  than  one  thread,  a  corresponding  number  of  teeth  will  be 
moved  by  each  revolution. 
With  the  increase  of  the 
number  of  threads,  the  side 
motion  of  the  wheel  and 
screw  is  accelerated ;  and 
when  the  threads  and  num- 
ber of  teeth  are  equal, an 
angle  of  45°  is  required  for 
teeth  and  thread,  provided 
their  diameters  also  are 
equal.  This  motion  causes 

a  great  deal  of  friction  and    ™. 

Fig.  320.    Worm  and  worm  wheel. 

it  is  only  resorted  to  where  no  other  means  can  be  employed  to 
produce  the  required  motion.  In  small  machinery,  the  worm  is 
frequently  made  use  of  to  produce  a  uniform,  uninterrupted 
motion ;  the  screw,  in  such  cases,  is  made  of  hardened  steel  and 
the  teeth  of  the  wheel  are  cut  by  the  screw  which  is  to  work  in 
the  wheel.  If  the  form  of  the  teeth  in  the  wheel  is  not  curved 
and  its  face  is  concave  so  as  to  fit  the  thread  in  all  points,  the 
screw  will  touch  the  teeth  but  in  one  point  and  cause  them  to  be 
liable  to  breakage. 


HANDBOOK    ON    ENGINEERING.  709 

PROPORTIONS  OF  TEETH  OF  WHEELS. 

Tooth*— -In  computing  the  dimensions  of  a  tooth,  it  is  to  be 
considered  as  a  beam  fixed  at  one  end,  the  weight  suspended 
from  the  other,  or  face  of  the  beam  ;  and  it  is  essential  to  con- 
sider the  element  of  velocity,  as  its  stress  in  operation,  at  high 
velocity  with  irregular  action,  is  increased  thereby.  The  dimen- 
sions of  a  tooth  should  be  much  greater  than  is  necessary  to  resist 
the  direct  stress  upon  it,  as  but  one  tooth  is  proportioned  to  bear 
the  whole  stress  upon  the  wheel,  although  two  or  more  are 
actually  in  contact  at  all  times ;  but  this  requirement  is  in 
consequence  of  the  great  wear  to  which  a  tooth  is  subjected? 
the  shocks  it  is  liable  to  from  lost  motion  when  so  worn  as  to 
reduce  its  depth  and  uniformity  of  bearing,  and  the  risk  of  the 
breaking  of  a  tooth  from  a  defect.  A  tooth  running  at  a  low 
velocity  may  be  materially  reduced  in  its  dimensions  compared 
with  one  running  at  high  velocity  and  with  a  like  stress.  The 
result  of  operations  with  toothed  wheels,  for  a  long  period  of 
time,  has  determined  that  a  tooth  with  a  pitch  of  3  inches  and  a 
breadth  7.5  inches  will  transmit,  at  a  velocity  of  6.66  feet  per 
second,  the  power  of  59.16  horses. 

TO    COMPUTE    THE    DEPTH    OF    A    CAST-IRON    TOOTH. 

1.  When  the  stress  is  given. 

Rule*  —  Extract  the  square  root  of  the  stress,  and  multiply  it 
by  .02. 

Example. — The  stress  to  be  borne  by  a  tooth  is  4886  Ibs. ; 
what  should  be  its  depth? 

1/4886  x  .02  =  Io4  in. 

2.  When  the  horse-power  is  given. 

Rule* — Extract  the  square-root  of  the  quotient  of  the  horse- 
power divided  by  the  velocity  in  feet  per  second,  and  multiply  it 
by  .466. 


710  HANDBOOK    ON    ENGINEERING. 

Example.  —  The  horse-power  to  be  transmitted  by  a  tooth  is 
60,  and  the  velocity  of  it  at  its  pitch-line  is  6.66  feet  per  second ; 
what  should  be  the  depth  of  the  tooth  ? 

60  x  .466  =  1.398  in. 


6.66 

TO    COMPUTE  THE   HORSE -POWER  OF  A  TOOTH. 

Rule*  —  Multiply  the  pressure  at  the  pitch-line  by  its  velocity 
in  feet  per  minute,  and  divide  the  product  by  33,000. 

CALCULATING  SPEED  WHEN  TIME  IS  NOT  TAKEN  INTO  ACCOUNT. 

Rule*  —  Divide  the  greater  diameter,  or  number  of  teeth, 
by  the  lesser  diameter  or  number  of  teeth,  and  the  quotient  is 
the  number  of  revolutions  the  lesser  will  make,  for  one  of  the 
greater. 

Example.  —  How  many  revolutions  will  a  pinion  of  20  teeth 
make,  for  1  of  a  wheel  with  125  ? 

125  divided  by  20  =±=  6.25  or  6J  revolutions. 

To  find  the  number  of  revolutions  of  the  last  to  one  of  the  first, 
in  a  train  of  wheels  and  pinions :  — 

Rule*  —  Divide  the  product  of  all  the  teeth  in  the  driving  by 
the  product  of  all  the  teeth  in  the  driven  ;  and  the  quotient  equals 
the  ratio  of  velocity  required. 

Example  1. — Required  the  ratio  of  velocity  of  the  last,  to  1 
of  the  first,  in  the  following  train  of  wheels  and  pinions,  viz. : 
pinions  driving  —  the  first  of  which  contains  10  teeth,  the  second 
15,  and  third  18.  Wheels  driven,  first  teeth  15,  second  25, 

10x15x18 
and  third  32.      ^ — ^ — ^-0  —  .225  of    a  revolution   the    wheel 

10  X  ^0  X  O& 

will  make  to  one  of  the  pinion. 

Example  2. — A  wheel  of  42  teeth  giving  motion  to  1  of  12, 
on  which  shaft  is  a  pulley  of  21  inches  diameter,  driving  1  of  6 ; 


HANDBOOK   ON    ENGINEERING.  711 

required  the  number  of  revolutions  of  the  last  pulley  to   1  of  the 

42x21 
first   wheel,     j^ g—  12.25  or  12J  revolutions. 

NOTE.  — Where  increase  or  decrease  of  velocity  is  required  to 
be  communicated  by  wheel- work,  it  has  been  demonstrated  that 
the  number  of  teeth  on  each  pinion  should  not  be  less  than  1  to 
6  of  its  wheel,  unless  there  be  some  other  important  reason  for  a 
higher  ratio. 

WHEN    TIME    MUST  BE    REGARDED. 

Rule*  —  Multiply  the  diameter  or  number  of  teeth  in  the  driver 
by  its  velocity  in  any  given  time,  and  divide  the  product  by  the 
required  velocity  of  the  driven ;  the  quotient  equals  the  number 
of  teeth  or  diameter  of  the  driven,  to  produce  the  velocity 
required. 

Example  1.  —  If  a  wheel  containing  84  teeth  makes  20  revolu- 
tions per  minute,  how  many  must  another  contain,  to  work  in 
contact,  and  make  60  revolutions  in  the  same  timer 
80  x  20  divided  by  60  =27  teeth. 

Example  2.  —  From  a  shaft  making  45  revolutions  per  minute 
and  with  a  pinion  9  inches  diameter  at  the  pitch-line,  we  wish 
to  transmit  motion  at  15  revolutions  per  minute ;  what,  at  the 
pitch-line,  must  be  the  diameter  of  the  wheel? 

45  x  9  divided  by  15  =  27  inches. 

Example  3.  —  Required  the  diameter  of  a  pulley  to  make  16 
revolutions  in  the  same  time  as  one  of  24  inches  making  36. 
24x36  divided  by  16  ==  54  inches. 

The  distance  between  the  centers,  and  the  velocities  of  two  wheels 
being  given,  to  find  their  proper  diameters :  — 

Rule*  —  Divide  the  greatest  velocity  by  the  least ;  the  quo- 
tient is  the  ratio  of  diameter  the  wheels  must  bear  to  each  other. 
Hence,  divide  the  distance  between  the  centers  by  the  ratio  -|-  1 ; 
the  quotient  equals  the  radius  of  Lhe  smellier  wheel ;  and  subtract 


712  HANDBOOK    ON    ENGINEERING. 

the  radius  thus  obtained  from  the  distance  between  the  centers ; 
the  remainder  equals  the  radius  of  the  other. 

Example.  — The  distance  of  two  shafts  from  center  to  center 
is  50  in.  and  the  velocity  of  the  one  25  revolutions  per  minute, 
the  other  is  to  make  80  at  the  same  time ;  the  proper  diameters 
of  the  wheels  at  the  pitch  line  are  required. 

80  divided  by  25=3.2,  ratio  of  velocity,  and  50  divided  by 
3.2+  1  =  11.9,  the  radius  of  the  smaller  wheel ;  then  50  minus 
11.9  =38.1,  radius  of  larger  ;  their  diameters  are  11.9x2  =  23.8 
and  38.1x2  =  76.2  in. 

To  obtain  or  diminish  an  accumulated  velocity  by  means  of 
wheels  and  pinions,  or  wheels,  pinions  and  pulleys,  it  is  necessary 
that  a  proportional  ratio  of  velocity  should  exist,  and  which  is 
thus  attained  ;  multiply  the  given  and  required  velocities  together ; 
and  the  square  root  of  the  product  is  the  mean  or  proportionate 
velocity. 

Example. — Let  the  given  velocity  of  a  wheel  containing  54 
teeth  equal  16  revolutions  per  minute,  and  the  given  diameter  of 
an  intermediate  pulley  equal  25  in.,  to  obtain  a  velocity  of  81 
revolutions  in  a  machine ;  required  the  number  of  teeth  in  the 
intermediate  wheel  and  diameter  of  the  last  pulley. 

->/  81x16  =  36  mean  velocity  ;  54  x  16  divided  by  36  =  24 
teeth,  and  25x36  divided  by  81  =  11.1  in.,  diameter  of  pulley. 

TABLE    OF    THE    WEIGHT    OF      A     SQUARE     FOOT     OF     SHEET    IRON    IN 
POUNDS    AVOIRDUPOIS. 

No.  1  is  T5^  of  an  inch  ;  No.  4,  J ;  No.  11,  -|,  etc. 

No.  on  wire  gauge,  1     2       3      4     5     6     7     8     9     10     11     12 
Poundsavoir.,       12.512    11     10    9     8  7.5    7     6    5.68    5   4.62 

No.  on  wire  gauge,   13   14    15   16   17      18       19       20 21       22 

Poundsavoir.,        4.31  4  3.95  3  2.5  2.18  1.93     1.62    1.5     1.37 


HANDBOOK    ON    ENGINEERING.  713 

SCREW-CUTTING . 

In  a  lathe  properly  adapted,  'screws  to  any  degree  of  pitch,  or 
number  of  threads  in  a  given  length,  may  be  cut  by  means  of  a 
leading  screw  of  any  given  pitch,  accompanied  with  change  wheels 
and  pinions  ;  coarse  pitches  being  effected  generally  by  means  of 
one  wheel  and  one  pinion  with  a  carrier,  or  intermediate  wheel, 
which  cause  no  variation  or  change  of  motion  to  take  place  ;  hence, 
the  following :  — 

Rule*  —  Divide  the  number  of  threads  in  a  given  length  of  the 
screw  which  is  to  be  cut,  by  the  number  of  threads  in  the  same 
length  of  the  leading  screw  attached  to  the  lathe,  and  the  quotient 
is  the  ratio  that  the  wheel  on  the  end  of  the  screw  must  bear  to 
that  on  the  end  of  the  lathe  spindle. 

Example. — Let  it  be  required  to  cut  a  screw  with  5  threads 
in  an  inch,  the  leading  screw  being  of  J  inch  pitch,  or  containing 
2  threads  in  an  inch  ;  what  must  be  the  ratio  of  wheels  applied  ? 

5  divided  by  2  =  2.5,  the  ratio  they  must  bear  to  each  other. 
Then  suppose  a  pinion  of  40  teeth  be  fixed  upon  for  the  spindle ; 
40  x  2.5  =  100  teeth  for  the  wheel  on  the  end  of  the  screw. 

But  screws  of  a  greater  degree  of  fineness  than  about  8  threads 
in  an  inch  are  more  conveniently  cut  by  an  additional  wheel  and 
pinion,  because  of  the  proper  degree  of  velocity  being  more 
effectively  attained,  and  these,  on  account  of  revolving  upon  a 
stud,  are  commonly  designated  the  stud- wheels,  or  stud-wheel 
and  pinion  ;  but  the  mode  of  calculation  and  ratio  of  screw  are  the 
same  as  in  the  preceding  rule.  Hence,  all  that  is  further  neces- 
sary is  to  fix  upon  any  three  wheels  at  pleasure,  as  those  for  the 
spindle  and  stud-wheels  ;  then  multiply  the  number  of  teeth  in 
the  spindle-wheel  by  the  ratio  of  the  screw  and  by  the  number  of 
teeth  in  that  wheel  or  pinion,  which  is  in  contact  with  the  wheel 
on  the  end  of  the  screw ;  divide  the  product  by  the  stud-wheel  in 
contact  with  the  spindle-wheel,  and  the  quotient  is  the  number  of 
teeth  required  in  the  wheel  on  the  end  of  the  leading  screw. 


714 


HANDBOOK   ON   ENGINEERING. 


Example.  —  Suppose  a  screw  is  required  to  be  cut  containing 
25  threads  in  an  inch,  and  the  leading  screw,  as  before,  having 
two  threads  in  an  inch,  and  that  a  wheel  of  60  teeth  is  fixed  upon 
for  the  end  of  the  spindle,  20  for  the  pinion  in  contact  with  the 
screw-wheel,  and  100  for  that  in  contact  with  the  wheel  on  the 
end  of  the  spindle ;  required  the  number  of  teeth  in  the  wheel  for 
the  end  of  the  leading  screw. 

25  divided  by  2  =  12.5,  and  6°X^Q5^20  =  150  teeth. 

Or  suppose  the  spindle  and  screw  wheels  to  be  those  fixed  upon, 
also  any  one  of  the  stud-wheels,  to  find  the  number  of  teeth  in  the 
other. 

150x100  60x12.5x20 

=  20  teeth,  or  -       ^^       -  —  100  teeth. 


60x12.5 


150 


Transmission  of  Power  by  Manilla  Rope, 
power  Transmitted. 


Horse- 


Feet  per  minute  .... 

1000 

1500 

2000 

2500 

3000 

3500 

4000 

4500 

5000 

Diameter  of  Rope      .  | 

((  U  I 

"  •  "  !  a 
"  "  .  14 
"  "  .  u 

<c  «  .  .2 

11 

31 
6* 

74 

10 
13 

21 
*i 
74 
11 
15 
194 

34 
64 
10* 
15 
20 
26 

44 
8 
13 
18 
25 
33 

54 
10 
15 
22 
30 
39 

64 

11 

18 
26 
35 
46 

7 
13 
20 
30 
40 
52 

8 
15 
23 
34 
45 
59 

9 
16 
26 
37 
50 
65 

Inches  Expressed  in  Decimals  of  a  Foot. 


1 

k 

1 

1 

2 

3 

4 

5 

.0208 

.0417 

.0626 

.0833 

.1667 

.2500 

.3333 

.4167 

6 

7 

8 

9 

10 

11 

12 

.5000 

.5833 

.6667 

.7610 

.8333 

.9167 

1.000 

HANDBOOK  ON  ENGINEERING. 


TABLE  OF  TRANSMISSION  OF  POWER  BY 
WIRE  ROPES. 

This  table  is  based  upon  scientific  calculations,  careful  observations 
and  experience,  and  can  be  relied  upon  when  the  distance  exceeds  100 
feet.  It  is  also  found  by  experience  that  it  is  best  to  run  the  wire  rope 
transmission  at  the  medium  number  of  revolutions  indicated  in  the  table, 
as  it  makes  the  best  and  smoothest  running  transmission.  If  more 
power  is  needed  than  is  indicated  at  80  to  100  revolutions,  choose  a 
larger  diameter  of  sheave. 


1 

Diameter  of 
Sheave  in  ft. 

Number  of 
Revolutions. 

Diameter  of 
Rope. 

Horse  - 
Power. 

Diameter  of 
Sheave  in  ft. 

Number  of 
Revolutions. 

Diameter  of 
Rope. 

Horse  - 
Power. 

3 

80 

| 

3 

7 

140 

A 

35 

3 

100 

| 

4 

8 

80 

1 

26 

3 

120 

1 

4 

8 

100 

1 

32 

3 

140 

4£ 

8 

120 

1 

39 

4 

80 

1 

4 

8 

140 

1 

45 

4 

100 

1 

5 

9 

80 

{At 

\  47 

i   48 

4 

120 

I 

6 

9 

100 

{At 

1    58 
/   60 

4 

140 

I 

7 

9 

120 

{At 

\   69 

/    73 

5 

30 

A 

9 

9 

140 

{At 

\    82 
/    84 

5 

100 

A 

11 

10 

80 

{t  H 

1    64 

;  es 

5 

120 

A 

13 

10 

100 

{t  H 

\   80 
/   85 

5 

140 

A 

15 

10 

120 

'{I  H 

1    96 

/102 

6 

80 

h 

14 

10 

140 

(M* 

\112 

hi9 

6 

100 

i 

17 

12 

80 

{HI 

Y    93 

/   99 

6 

120 

i 

20 

12 

100 

{HI 

\116 
/  124 

6 

140 

* 

23 

12 

120 

{HI 

\140 
J  149 

7 

80 

A 

20 

12 

120 

i 

173 

7 

100 

A 

25 

14 

80 

{"< 

1141 
J  148 

7 

120 

A 

30 

14 

100 

{"• 

\176 
J  185 

716  HANDBOOK   ON   ENGINEERING. 


CHAPTER    XXV. 
ELECTRIC  ELEVATORS. 

In  factories,  warehouses  and  business  buildings,  freight,  and  in 
some  instances  passenger  elevators,  are  operated  by  machines 
that  are  arranged  to  be  driven  by  a  belt.  Such  machines  are 
variously  called  belted  elevators,  factory  elevators  and  sometimes 
warehouse  elevators. 

In  factories  where  there  is  a  line  of  shafting  kept  running 
continuously,  they  are  driven  from  it.  As  a  rule  the  elevator 
machine  is  driven  from  a  countershaft  which  latter  is  belted  to 
the  line  shaft.  Very  often  the  elevator  machine  is  driven 
directly  from  the  line  shaft.  As  the  line  shaft  runs  always  in  the 
same  direction,  the  only  way  in  which  the  elevator  machine  can 
be  made  to  run  in  both  directions  is  by  the  use  of  two  belts,  one 
open  and  the  other  crossed,  or  some  form  of  gearing  that  will 
accomplish  the  same  result.  The  common  practice  is  to  use 
double  belts.  Either  one  of  these  belts  can  be  made  to  drive  by 
using  friction  clutches,  or  by  having  tight  and  loose  pulleys,  and 
a  belt  shifter.  The  latter  arrangement  is  the  most  common. 

In  buildings  where  there  is  no  line  of  shafting,  power  for  oper- 
ating the  elevator  machine  must  be  derived  from  some  kind  of 
motor  installed  expressly  for  the  purpose.  Nowadays  electric 
motors  are  very  extensively  used  for  this  purpose,  and  the  com- 
bination of  an  elevator  machine  and  an  electric  motor  to  drive  it  is 
very  generally  called  an  electric  elevator,  although  in  reality  it  is  not 
such,  but  simply  a  belted  elevator  machine  driven  by  an  electric 
motor.  It  has  become  so  common,  however,  to  call  such  com- 
binations electric  elevators,  that  true  electric  elevators  are  generally 
designated  as  "  direct  connected  electric  elevators." 


HANDBOOK   ON   ENGINEERING.  711 

The  first  impression  would  be  that  in  the  combination  of  a 
belted  elevator  machine,  and  an  electric  motor  to  drive  it,  as  the 
motor  simply  furnishes  the  power  to  set  the  machine  in  motion, 
there  can  be  nothing  about  the  combination  that  requires  any 
special  elucidation.  Such  a  conclusion,  however,  would  not  be 
correct,  for  there  are  several  ways  in  which  the  combination  can 
be  arranged,  and  in  what  follows  we  propose  to  explain  these 
several  combinations,  pointing  out  the  important  features  of 
each. 

The  simplest  way  in  which  a  motor  can  be  installed  to  drive 
an  elevator,  is  to  arrange  it  so  as  to  drive  the  counter  shaft  con- 
tinuously, in  which  case  the  elevator  is  stopped  and  started  by 
throwing  the  belts  on  the  tight  or  the  loose  pulley.  Although 
this  is  a  very  simple  arrangement,  it  is  not  desirable  unless  the 
elevator  is  kept  in  service  all  the  time.  In  buildings  where  the 
elevator  is  used  only  at  intervals,  a  great  amount  of  power  is 
wasted  if  the  shafting  is  kept  running  all  the  time ;  hence  it  is 
desirable  to  arrange  the  motor  so  that  it  can  be  stopped  when  the 
elevator  is  stopped,  and  started  whenever  the  elevator  is  to  be 
used. 

If  the  motor  is  arranged  so  as  to  run  all  the  time,  it  is  provided 
with  a  simple  motor-starting  switch,  the  same  as  is  used  for  any 
motor  installed  to  operate  machinery  of  any  kind.  If  the  motor 
is  started  and  stopped  whenever  the  elevator  is  started  and  stopped, 
it  is  necessary  to  provide  a  motor-starter  that  can  be  operated 
from  the  elevator  car.  A  very  common  way  of  arranging  a  motor 
to  start  and  stop  with  the  elevator  is  illustrated  in  the  diagram 
Fig.  321. 

In  this  diagram  the  elevator  car  is  shown  at  (7,  with  the  lifting 
ropes  running  over  the  sheave  F  at  the  top  of  the  elevator 
shaft,  and  then  down  and  around  the  drum  A  of  the  elevator 
machine.  This  drum  is  driven  by  means  of  screw  gearing,  as  a 
rule,  with  driving  pulleys  on  the  screw  shaft  as  shown  at  B.  The 


718 


HANDBOOK    ON    ENGINEERING. 


driving  motor  is  shown  at  Jf,  and  the  counter-shaft  to  which  it  is 
belted  is  at  D.  In  this  arrangement  the  elevator  machine  is  pro- 
vided with  a  tight  center  pulley  and  loose  pulleys  on  the  two  sides. 
The  belts  are  shown  on  the  loose  pulley  s?  one  being  open  and  the 


Fig*  321.    Belt  driven  electric  elevator. 

other  being  crossed  „  The  countershaft  carries  a  drum  wide 
enough  to  allow  for  the  side  movement  of  the  belts  when  one  or 
the  other  is  shifted  upon  the  tight  center  pulley  by  the  belt  shifter 
$.  To  operate  the  elevator  car,  a  hand  rope  is  provided  which 


HANDBOOK    ON    ENGINEERING.  719 

runs  up  the  elevator  shaft  at  one  side  of  the  car  from  bottom  to 
top  of  building.  This  rope  is  shown  in  the  diagram  at  J,  and 
runs  around  two  small  sheaves  a  a.  The  lower  one  of  these  sheaves 
is  provided  with  a  crank  pin,  which  moves  the  connecting  rod  6, 
and  thus  rocks  the  lever  r,  and  thereby  moves  the  belt  shifter  s. 
To  cause  the  car  to  ascend  the  hand  rope  I  is  pulled  down,  and 
to  make  the  car  descend,  the  hand  rope  is  pulled  up.  As  will  be 
seen  from  this  explanation,  the  lower  sheave  a  will  rotate  in  one 
direction  when  the  hand  rope  is  pulled  to  make  the  car  go  up,  and 
in  the  opposite  direction  when  the  rope  is  pulled  to  make  the  car 
run  down.  In  the  diagram,  sheave  a  is  shown  in  the  stop  posi- 
tion, therefore  when  the  hand  rope  is  pulled  down  so  as  to  make 
the  car  run  up,  the  sheave  will  turn  in  a  direction  opposite  to  the 
movement  of  the  hands  of  a  clock,  and  thus  the  belt  shifter  will 
be  moved  to  the  right,  and  the  open  belt  will  be  run  onto  the  tight 
center  pulley.  If  the  hand  rope  is  pulled  up  sheave  a  will  rotate 
in  the  direction  of  the  hands  of  a  clock,  and  the  belt  shifter  will 
move  toward  the  left  and  thus  shift  the  crossed  belt  onto  the  tight 
pulley.  The  rope  p  is  a  stop  rope  and  is  connected  with  the  two 
sides  of  the  hand  rope  in  the  manner  shown,  so  that  when  the  car 
is  running  in  either  direction,  if  p  is  pulled  hard  it  will  bring  I  to 
the  position  shown  in  the  diagram,  and  thus  stop  the  car.  This 
rope  can  be  dispensed  with,  but  the  objection  is  that  in  pulling 
the  hand  rope  I  to  stop  the  car  it  may  be  pulled  too  far  and  then 
the  car  will  not  only  be  stopped  but  it  will  be  caused  to  run  in 
the  opposite  direction. 

The  motor  starting  switch'is  shown  at  E,  the  line  wires  being 
connected  with  the  two  top  binding  posts.  The  lever  c  c  is  in  one 
piece  and  is  independent  of  lever  e,  but  both  swing  around  the 
same  pivot.  At  m,  a  dash  pot  is  provided  which  acts  to  prevent 
the  too  rapid  movement  of  lever  e.  As  will  be  noticed,  lever  c 
has  a  projection  which  holds  lever  e  up.  The  operation  of  this 
motor  starter  is  as  follows :  When  the  hand  rope  I  is  pulled  in 


720  HANDBOOK    ON    ENGINEERING. 

either  direction,  the  rope  h  draws  lever  c  towards  the  left  and 
causes  it  to  make  contact  with  the  switch  jaw./.  In  this  way  the 
current  from  the  upper  binding  post  which  is  connected  with  j 
through  wire  g,  passes  to  lever  e,  and  thus  to  the  starting  resist- 
ance, which  is  indicated  by  the  dotted  lines  t,  to  binding  post  ft, 
from  where  it  goes  to  the  motor  armature  through  wire  d,  and  re- 
turns through  the  other  wire  d  to  the  upper  binding  post  at  the 
right  side,  which  is  connected  with  the  opposite  side  of  the  main 
line,  thus  completing  the  circuit.  The  field  current  branches  off 
from  the  upper  end  of  the  starting  resistance  i  and  reaches  the 
field  coils  through  wire /,  and  through  the  lower  wire  /  reaches 
the  return  armature  wire  d  and  thus  the  opposite  side  of  the  cir- 
cuit. When  the  rope  h  pulls  lever  c  over  toward  the  left,  the  lever 
e  does  not  follow  it,  as  it  is  held  up  by  the  dash  pot  m.  The 
weight  on  the  end  of  e  gradually  overcomes  the  resistance  of  the 
dash  pot,  and  thus  causes  lever  e  to  move  downward  slowly.  The 
velocity  at  which  e  moves  downward  is  graduated  by  adjusting 
the  opening  in  the  dash  pot  through  which  the  oil  flows. 

From  the  foregoing  it  will  be  seen  that  the  starter  E  is  made  so 
as  to  accomplish  automatically  just  what  a  man  accomplishes 
when  he  moves  the  lever  of  an  ordinary  motor-starter ;  that  is,  it 
first  closes  the  circuit  through  the  motor,  by  bringing  lever  c  into 
contact  withj;  and  then  allows  lever  e  to  move  slowly  so  as 
to  cut  the  resistance  i  out  of  the  armature  circuit  gradually. 
When  the  elevator  is  stopped,  by  pulling  the  hand  rope  I  to  the 
stop  position,  the  rope  h  slacks  up  and  then  the  weight  on  the  end 
of  lever  c  causes  it  to  descend,  and  thus  return  lever  e  to  the  posi- 
tion shown  in  the  diagram,  and  also  to  break  the  circuit  between 
c  and  j. 

The  elevator  machine  A  is  provided  with  a  brake,  which  is 
actuated  by  the  belt  shifter  s,  so  that  when  the  belts  are  shifted 
upon  the  side  pulleys,  as  shown  in  the  diagram,  the  brake  is  put 
on,  and  thus  the  machine  is  stopped.  As  soon  as  the  belt  shifter 


HANDBOOK    ON   ENGINEERING.  721 

is  moved  to  set  the  car  in  motion  the  brake  is  raised,  so  as  to 
allow  the  machine  to  run  free. 

This  arrangement  is  used  very  extensively,  although  the  motor- 
starting  switch  is  not  always  made  in  strict  accordance  with  the 
one  shown  at  E.  In  fact,  there  are  a  great  many  different  designs 
on  the  market,  but  they  all  accomplish  the  same  result,  although 
the  means  employed  may  be  very  different. 

Although  it  is  very  advantageous  to  have  the  motor  arranged 
as  in  Fig.  321,  so  that  it  may  be  stopped  and  started  together  with 
the  elevator,  there  is  one  objection  to  it  which  is  sometimes  re- 
garded as  serious,  and  that  is,  that  as  it  requires  a  great  amount 
of  power  to  start  an  elevator  from  a  state  of  rest,  the  motor  will 
take  a  very  strong  current  in  the  act  of  starting.  To  get  around 
this  objection,  it  is  a  common  practice  to  provide  a  separate  rope 
for  starting  the  motor,  and  then  when  it  is  desired  to  use  the  ele- 
vator, the  motor  rope  is  pulled  first,  and  in  half  a  minute  or  so, 
the  main  hand  rope  is  pulled.  In  this  way  the  motor  gets  a  start 
ahead  of  the  elevator.,  and  the  headway  of  the  motor  armature 
helps  to  set  the  elevator  car  in  motion,  so  that  the  current  taken 
by  the  motor  to  start  the  elevator  is  very  much  reduced. 

When  a  separate  rope  is  used  to  start  the  motor  in  advance  of 
the  elevator,  the  starter  E,  or  the  levers  connecting  with  it,  are 
made  so  that  while  the  motor  can  be  started  independently  of  the 
elevator  car,  when  the  main  hand  rope  is  pulled,  to  stop  the  car, 
it  also  stops  the  motor.  If  this  arrangement  were  not  provided, 
the  operator  might  stop  the  elevator  and  forget  to  stop  the  motor, 
in  which  case  the  latter  would  keep  on  running  and  waste  power. 

The  main  hand  rope  I  is  provided  with  stops  at  top  and 
bottom  of  the  elevator  shaft,  so  that  the  car  may  be  stopped  auto- 
matically should  the  operator  forget  to  pull  the  hand  rope  at  the 
proper  time. 

It  is  the  universal  practice  with  elevator  machines  of  the  type 
shown  in  Fig.  321  to  counterbalance  the  elevator  car,  but  we  have 
not  shown  a  counterbalance  in  this  diagram  as  it  would  only  serve 


722 


HANDBOOK    ON    ENGINEERING. 


to  complicate  its  appearance,  and  it  is  not  necessary  to  show  it  as 
the  electrical  features  will  be  the  same  whether  there  is  a  counter- 
balance or  not.  This  diagram  also  shows  a  separate  rope  h  for 
actuating  the  starter  E,  but  in  actual  machines  E  is  generally 


CONTROLLER 


ELEVATOR 


MOTOR 


Fig.  322.    Connections  of  gravity  motor  controller. 


rig.  ozz.     ^oniieciioiis  01  gruviij   iiioior  coin    uiivr. 
operated  from  the  lower  sheave  a,  which  also  actuates  the  belt 

shifter. 

Fig.  322  is  a  diagram  tnat  shows  the  way  in  which  one  of  the 
various  motor  starters  in  actual  use  is  connected  with  the  motor 


HANDBOOK    ON    ENGINEERING, 


723 


and  the  operating  hand  rope.  In  this  illustration  A  is  the  lower 
sheave  a  of  Fig.  321,  and  ^represents  the  hoisting  drum  and  E  the 
driving  pulleys  of  the  elevator  machine,  G  being  the  lifting  ropes 
from  which  the  car  is  suspended.  The  sheave  A  is  rotated 


MOTOR. 


Fig.  328.    Gravity  controller  with  rope  attachment, 
through  one  quarter  of  a  turn  in  either  direction  by  the  pull  on 

the  hand  rope  J5,  and  when  so  rotated  shifts  the  belt  shifter  and 
also  lifts  the  brake  from  the  brake-wheel.  At  the  same  time  the 
crank  pin  C  pulls  up  the  connecting  rod,  and  thus  the  upper  end 


724  HANDBOOK    ON    ENGINEERING. 

of  rod  c,  which  takes  the  place  of  lever  c  in  Fig.  321.  In  this 
way  the  switch  blades  in  the  lower  end  of  c  are  raised  into  con- 
tact with  the  clips  jf/,  which  take  the  place  of  contact  Jin  Fig.  321, 
and  thus  the  circuit  is  closed.  A  projection  s  on  c  holds  the 
switch  e  in  the  upper  position,  but  when  c  is  raised,  s  goes  up  with 
it,  and  then  e  is  free  to  descend  by  the  force  of  gravity  acting 
upon  the  weight  w.  The  dash  pot  m  is  set  so  as  to  retard  the 
movement  of  e  as  much  as  may  be  desired.  The  outer  end  of  e 
glides  over  the  contacts  i  in  its  downward  movement,  and  thus 
cuts  out  of  the  armature  circuit  the  starting  resistance.  This 
resistance  is  contained  in  the  controller  box. 

Fig,  323  shows  the  same  type  of  controller  as  in  Fig.  322,  but  it 
is  arranged  so  that  the  motor  may  be  started  ahead  of  the  elevator. 
The  separate  motor-starting  rope  is  shown  at  H.  When  this  rope 
is  pulled,  it  elongates  the  spiral  spring  K  which  is  connected  with 
the  stud  6r  fixed  in  the  upper  end  of  rod  c.  The  rope  H  is  pulled 
up  enough  to  stretch  K  until  the  lever  Z>is  lifted,  H  being  attached 
to  its  outer  end  I.  When  D  is  lifted  sufficiently,  its  inner  end  dis- 
engages the  stud  G,  and  allows  it  to  slide  upward  in  the  slot 
shown  in  dotted  lines,  in  the  lower  end  of  the  connecting  rod. 
In  this  way  the  motor  is  started  ahead  of  the  elevator  machine. 
If  now  the  elevator  machine  is  started,  by  pulling  on  the  main 
hand  rope  FF,  the  crank  pin  C'  on  the  hand  rope  sheave  will  lift 
the  connecting  rod  (7,  and  when  it  reaches  its  upper  position,  the 
catch-lever  D  will  drop  into  the  position  shown  in  the  illustration, 
and  thus  lock  the  stud  Gr,  so  that  when  the  elevator  is  stopped, 
the  rotation  of  the  hand  rope  sheave  will  push  rod  G  downward 
and  thus  stop  the  motor,  as  well  as  shift  the  belts  and  stop  the 
elevator  machine. 

In  the  three  illustrations  shown  the  motor  is  run  always  in  the 
same  direction  and  the  reversing  of  the  direction  of  rotation  of 
the  hoisting  drum  is  effected  by  the  use  of  double  belts  and  a 
belt  shifter,  or  friction  clutches,  which  cause  one  or  the  other  of 


HANDBOOK    ON    ENGINEERING.  725 

the  belts  to  do  the  driving.     The  way  in  which  machines  of  this 


726  HANDBOOK    ON    ENGINEERING. 

This  figure  shows  the  position  of  the  motor,  the  countershaft 
and  the  elevator  machine  with  reference  to  the  elevator  shaft. 
This  illustration  is  so  clear  that  an  explanation  of  it  would  be 
superfluous. 

In  relation  to  the  installation  of  elevator  plants  of  this  type 
all  that  need  be  said  is  that  the  motor  must  be  of  the  shunt 
type,  the  same  as  those  used  for  driving  machines  of  any  kind. 
A  series  wound  motor,  such  as  are  used  for  electric  railway 
cars,  must  not  be  used.  Shunt  wound  motors  cannot  run  above  a 
certain  speed,  unless  forced  to  do  so  by  power  applied  from  an 
external  source,  and  in  such  an  event  they  become  generators  of 
electricity  and  thus  resist  rotation.  On  this  account,  when  they 
are  used  for  elevator  service,  they  not  only  move  the  elevator  car, 
but  when  the  latter  is  descending  under  the  influence  of  a  heavy  load 
and  tends  to  run  away,  the  motor,  at  once  begins  to  act  as  a  gen- 
erator, and  is  thus  converted  into  a  brake,  which  holds  the  car  and 
prevents  it  from  attaining  a  speed  much  above  the  normal ;  in 
fact,  the  difference  between  the  car  velocity  when  lifting  a  heavy 
load,  and  when  running  down  under  the  influence  of  a  similar  load 
is  hardly  enough  to  be  noticed  by  any  one  not  familiar  with  the 
elevator. 

The  motor  in  these  combinations  is  to  be  given  the  same  care 
as  those  used  for  other  purposes ;  that  is,  it  must  be  kept  clean 
and  the  brushes  properly  set  so  as  to  run  with  as  little  spark  as 
is  possible.  The  controller  switch  requires  more  attention  than  the 
motor  starters  used  with  stationary  motors,  for  the  simple  reason 
that  it  is  used  to  a  much  greater  extent.  Every  time  the  elevator 
is  started  or  stopped  the  controller  switch  is  actuated,  hence,  the 
switch  levers  are  subjected  to  a  considerable  amount  of  wear,  and 
the  contacts  are  liable  to  become  rough,  either  by  cutting  or  by 
being  burned  on  account  of  making  imperfect  contact.  On  this 
account  the  contact  must  be  well  examined  at  least  once  every 
day,  and  if  burned  or  rough  must  be  smoothed  up.  It  is  also 


HANDBOOK   ON   ENGINEERING. 


727 


necessary  to  see  that  all  parts  of  the  controller  are  properly  se- 
cured, that  none  of  the  screws  or  pins  are  working  out,  and  that 
the  contacts  and  switch  levers  are  not  out  of  their  normal  posi- 
tion. 


Fig.  325.    Wiring  used  with  reversible  motor. 

As  electric  motors  can  be  run  as  well  in  one  direction  as  the 
other,  and  as  all  that  is  required  to  make  any  motor  reversible  is 
to  provide  a  reversing  switch,  it  can  be  seen  at  once  that  by  mak- 
ing use  of  such  a  switch,  the  direction  of  movement  of  the  ele« 


728  HANDBOOK    ON    ENGINEERING. 

vator  car  can  be  reversed  by  simply  reversing  the  motor,  and  thus 
do  away  with  the  complication  of  a  countershaft  and  tight  and 
loose  pulleys.  Owing  to  this  fact  elevator  machines  are  now 
made  so  as  to  be  used  with  reversing  motors.  These  are  usually 
called  single-belt  machines.  The  way  in  which  such  machines 
are  connected  with  the  motor  and  the  type  of  controller  required 
can  be  understoood  from  the  diagram  Fig.  325. 

As  will  be  seen,  the  principal  difference  in  the  machine  itself 
is  that  the  tight  and  loose  pulleys  are  replaced  by  a  single  tight 
pulley,  which  is  only  wide  enough  to  carry  the  driving  belt. 
Usually  an  extra  pulley  is  provided  for  the  brake,  and  this  brake 
is  mechanically  operated  in  the  same  manner  as  upon  machines 
provided  with  shifting  belts.  Another  modification,  which  is 
sometimes  used,  but  is  not  shown  in  the  diagram,  is  the  arrange- 
ment of  a  brake  so  that  same  is  operated  by  a  magnet 
instead  of  by  mechanical  means.  With  this  arrangement  the 
magnet  is  arranged  so  that  when  the  machine  is  in  motion,  the 
current  passing  through  the  magnet  coil  acts  to  lift  the  brake, 
and  when  the  machine  stops,  the  magnet  lets  go,  and  the  brake 
goes  on.  By  arranging  the  brake  in  this  way  it  becomes  perfectly 
safe ;  for  if  the  brake  magnet  fails  to  act,  the  brake  will  not  be 
raised,  and  the  machine  will  not  move ;  that  is,  failure  of  the 
device  to  work  properly  will  not  permit  the  elevator  car  to  move, 
thus  calling  attention  to  the  fact  that  something  is  out  of  order. 

The  operation  of  the  reversing  controller  is  as  follows :  the 
current  from  the  line  wires  passes  along  the  dotted  connections 
h  h  to  the  contacts  1,1,  i,i.  The  upper  left  hand  i  contact  is  con- 
nected with  the  lower  right  hand  one,  and  the  upper  right  hand 
with  the  lower  left  hand.  The  switch  lever  c  is  connected  with 
lever  e  by  means  of  the  two  springs  r  r,  so  that  c  may  be  moved 
either  up  or  down  without  carrying  e  with  it.  The  curved  con- 
tact o  is  connected  with,/,  while  g  is  connected  with  the  ends  of  the  start- 
ing resistance  n  n  by  means  of  the  wire  /  and  the  two  wires  s  s.  The 


HANDBOOK   ON   ENGINEERING.  729 

contacts  y  y  are  connected  to  k  and  the  lower  left-hand  contact  i  is  con- 
nected to  x.  If  the  hand  rope  I  is  pulled  so  as  to  carry  lever  c  upward, 
the  current  from  the  left  side  line  wire  will  pass  through  the  upper  left 
side  contact  i,  to  o,  thence  to  j  and  through  wire  b  to  the  motor  arma- 
ture, returning  through  the  other  b  wire  to  gr,  then  via  /  and  lower  s  to 
the  lower  end  of  n,  over  the  lever  e,  to  the  inner  end  of  lever  c  which  will 
be  in  contact  with  the  upper  right-hand  i  contact  and  finally  to  the  right 
side  line  wire.  The  current  for  the  field  magnet  coils  will  be  drawn  from 
the  upper  left  side  i  contact  to  the  adjacent  y  contact,  thence  to  con- 
tact k,  through  the  fields  and  back  to  x,  finally  to  the  left  side  line  wire. 
As  lever  c  has  been  moved  upward,  the  upper  spring  r  will  be 
compressed,  and  the  lower  one  will  be  stretched,  hence  a  force 
will  be  exerted  to  move  e  downward  over  the  lower  contacts  n  and 
thus  cut  out  the  starting  resistance.  As  in  the  case  of  the  con- 
troller in  Fig.  321  the  dash  pot  m  by  its  resistance  retards  the  move- 
ments of  e,  so  as  to  cut  out  the  resistance  as  gradually  as  may  be 
desired. 

In  the  chapter  on  stationary  motors  it  is  shown  that  to  prevent 
destructive  sparking,  when  the  starting  switch  is  opened,  the 
armature  and  field  coils  are  connected  so  as  to  form  a  permanently 
closed  loop.  This  style  of  connection  is  used  in  the  non-revers- 
ing controller  of  Fig.  321,  but  it  cannot  be  employed  with  a  re  vers- 
ing controller,  because  both  ends  of  the  armature  circuit  must  be 
free,  so  that  they  may  be  reversed  when  the  direction  of  rotation 
is  reversed.  As  this  connection  cannot  be  made,  a  very  common 
expedient  resorted  to  to  prevent  serious  sparking  when  the  switch 
is  opened  is  to  connect  a  string  of  incandescent  lamps  across  the 
terminals  of  the  field  circuit,  as  is  indicated  at  v  v  v.  These 
lamps,  together  with  the  field  coils,  form  a  closed,  circuit,  so  that 
when  the  switch  is  opened,  the  field  can  discharge  through  the 
lamps,  and  thus  avoid  sparking  at  the  controller  contacts.  The 
only  objection  to  this  arangement  is  that  all  the  current  that 
passes  through  the  lamps  is  wasted,  but  by  placing  two  or  three 


730  HANDBOOK    ON    ENGINEERING. 

in  series  the  loss  is  reduced  to  an  insignificant  amount.  Another 
way  in  which  the  sparking  is  subdued,  but  only  to  a  slight  ex- 
tent, is  by  connecting  the  brake  magnet  coil  with  the  binding 
posts  x  and  fc,  which  is  the  simplest  and  most  generally  used  con- 
nection. The  brake  magnet  coil  together  with  the  field  coils  form 
a  closed  loop  when  connected  with  x  and  ft,  but  when  the  main  cir- 
cuit is  opened,  the  currents  flowing  in  the  two  coils  meet  each  other 
at  x  and  ~k  flowing  in  opposite  directions,  hence  they  both  follow 
along  the  main  circuit  and  try  to  jump  across  the  gaps  at  the 
switch,  and  thus  produce  about  as  much  sparking  as  if  they  were 
connected  independently  of  each  other.  In  tracing  out  the  path 
of  the  current  when  lever  c  is  moved  upward,  it  was  shown  that  the 
left  side  line  went  directly  to  the  upper  commutator  brush.  Now 
when  c  is  moved  downward,  this  same  line  wire  runs  to  the  lower 
commutator  brush  since  the  connections  between  the  two  upper 
i  contacts  and  the  two  lower  ones  are  crossed.  To  reverse  the 
direction  of  rotation  of  a  motor  all  that  is  required  is  to  reverse 
the  direction  of  the  current  through  the  armature,  that  through 
the  field  remaining  unchanged,  hence  it  will  be  seen  that  by  cross- 
ing the  connections  between  the  upper  and  lower  i  contacts,  the 
direction  of  rotation  of  the  motor  is  reversed  when  the  c  lever  is 
moved  in  opposite  directions. 

DIRECT  CONNECTED  ELECTRIC  ELEVATORS. 

The  machines  explained  in  the  foregoing  pages  are  simply 
combinations  of  an  electric  motor  and  a  belt  driven  electric  ma- 
chine, but,  as  already  stated,  they  are  commonly  spoken  of  as 
44  electric  elevators."  In  what  follows  it  is  proposed  to  explain 
the  construction  and  operation  of  true  electric  elevators,  which 
are  called  44  direct  connected  machines  "  to  distinguish  them  from 
the  combinations  so  far  described. 

There  are  many  designs  of  direct  connected  electric  elevators 


HANDBOOK    ON    ENGINEERING. 


731 


now  upon  the  market,  and  it  would  be  out  of  the  question  to  un- 
dertake to  describe  all  of  them  in  the  space  that  can  be  devoted 
to  the  subject  in  this  book.  On  that  account  the  discussion  will 
be  confined  to  the  designs  that  are  most  extensively  used.  The 
explanations  here  given,  however,  will  be  sufficient  to  enable  any 


Fig.  326.    The  Otis  direct  connected  elevator. 

one  to  understand  the  operation  of  any  of  the  machines  not  de- 
scribed because  the  difference  in  the  principle  of  operation  is 
only  slight. 


732  HANDBOOK   ON   ENGINEERING. 

Perhaps  the  type  of  direct  connected  electric  elevator  that 
is  most  extensively  used  is  the  Otis  drum  elevator  with  hand 
rope  control  which  is  illustrated  in  Fig.  326.  This  machine  has 
been  upon  the  market  for  twelve  years  or  more,  and  is  still  one  of 
the  standard  Otis  machines.  It  is  called  a  hand  rope  control 
machine  because  the  starting  and  stopping  is  controlled  by  the 
movement  of  a  hand  rope  that  passes  through  the  elevator  car. 
In  the  illustration,  the  sheave  around  which  the  hand  rope  passes 
can  be  seen  located  on  the  front  end  of  the  drum  shaft.  In  a 
modification  of  the  design,  this  sheave  is  mounted  upon  a  sep- 
erate  shaft  but  the  way  in  which  it  acts  is  the  same  as  in  the  pres- 
ent design.  When  the  hand  rope  is  pulled  the  sheave  is 
rotated  and  the  horizontal  bar,  running  from  it  to  the 
controller  box,  which  is  mounted  on  top  of  the  motor? 
shifts  the  starting  switch  so  as  to  run  the  machine  in 
the  direction  desired.  At  the  same  time,  the  vertical  lever  ex- 
tending upward  from  the  side  of  the  brake  wheel,  lifts  the  brake 
and  thus  frees  the  motor  shaft  so  that  it  may  revolve  unobstructed. 
The  motor  carries  a  worm  on  the  end  of  the  armature  shaft  which 
gears  into  the  under  side  of  a  worm  wheel  mounted  upon  the 
drum  shaft.  This  worm  wheel  runs  in  a  casing  seen  just  back  of 
the  hand  rope  sheave  wheel.  The  sheave  mounted  upon  the  shaft 
directly  above  the  drum  is  for  the  purpose  of  guiding  the  coun- 
terbalance ropes,  which  run  up  from  the  back  of  the  drum.  In 
some  buildings  these  ropes  can  be  run  up  straight  from  the  back 
of  the  drum,  but  in  most  cases  they  must  run  up  in  the  elevator 
shaft  in  the  space  between  the  car  and  the  side  of  the  shaft.  As 
these  ropes  wind  upon  the  drum  from  one  side  to  the  other,  the 
guiding  sheave  must  move  endwise  on  the  shaft,  hence  it  is  called 
a  traveling,  or  vibrating  sheave.  The  levers  seen  projecting  to 
the  right  of  the  machine  from  a  small  shaft  just  above  the  drum 
are  what  is  called  a  slack  cable  stop,  and  their  office  is  to  stop 
the  machine  if  the  lifting  cable  becomes  slack  through  the  wedg- 


HANDBOOK    ON   ENGINEERING.  733 

ing  of  the  car  in  the  elevator,  shaft  or  any  other  cause.  These 
levers  are  held  in  the  position  shown  when  the  lifting  ropes  are 
tight,  but  drop  out  of  position  if  the  rope  slackens  up,  and  in 
dropping  they  release  a  lever,  which  holds  the  weight  seen  under 
the  hand  rope  sheave.  The  movement  of  this  lever  operates  a 
catch  that  engages  with  the  hand  rope  sheave  and  thus  the  hori- 
zontal bar  that  operates  the  brake  and  the  controller  switch  is 
brought  to  the  stop  position  and  the  rotation  of  the  hoisting  drum 
is  stopped. 

The  hand  rope  has  fastened  to  it  at  the  top  and  bottom  of  the 
elevator  shaft  stops  that  are  moved  by  the  car  when  it  reaches 
either  end  of  its  travel,  and  thus  the  elevator  machine  is  stopped 
automatically.  This  arrangement  is  the  same  as  that  used  with 
the  belt  driven  machines  already  described,  but  as  an  additional 
safety,  a  stop  motion  is  provided  on  the  machine  itself,  so  that  if 
the  stops  on  the  hand  rope  become  displaced,  the  car  will  still  be 
stopped  automatically  at  the  top  and  bottom  landings.  This  stop 
motion  is  seen  on  the  end  of  the  shaft,  just  in  front  of  the  hand 
rope  sheave,  and  consists  of  a  nut  that  travels  on  the  shaft  as  the 
latter  revolves.  At  both  sides  of  the  screw  there  are  projection 
cases  upon  the  inclosing  frame,  which  are  struck  by  the  traveling 
nut  when  it  comes  near  enough  to  either  end.  When  the  nut 
strikes  the  projection,  the  hand  rope  sheave  is  revolved  with  the 
shaft  and  thus  the  machine  is  stopped.  To  understand  this  ac- 
tion it  must  be  remembered  that  the  hand  rope  sheave  does  not 
revolve  except  when  turned  by  the  pull  on  the  hand  rope  or  by 
the  action  of  the  slack  cable  stop  or  the  traveling  nut. 

The  controller  box  on  top  of  the  motor  contains  the  starting 
resistance,  the  starting  and  reversing  switch,  and  also  a  magnet 
to  actuate  a  switch  that  gradually  cuts  out  the  starting  resistance. 
The  way  in  which  the  switches  act  to  start  and  stop  the  motor 
can  be  readily  explained  by  the  aid  of  the  diagram  Fig.  327. 

This  shows  the  circuit  connections  in  the  simplest  possible 


734 


HANDBOOK    ON    ENGINEERING. 


form.     In  this  diagram  all  the  wires  whose  presence  would  make 

t 


SArETY  MAGNET  FOR 
BRAKE  ON  MA  CHINE 


SHUNT  FILLD 

Fig.  327.    Diagram  of  controller  box  and  wiring. 

the  drawing  confusing  have  been  removed,  but  the  manner  in 


HANDBOOK   ON   ENGINEERING.  735 

which  they  are  connected  will  be  readily  understood  from  the 
following  explanation :  — 

The  main  switch,  which  connects  the  motor  circuits  with  the 
line,  is  located  at  the  upper  left  hand  corner  of  the  diagram,  the 
main  line  wires  being  marked-}-  and  —  .  When  this  switch  is 
closed,  the  motor  circuits  are  connected  with  the  line,  but  the 
motor  circuit  itself  is  not  closed  so  long  as  the  switch  M  remains 
in  the  position  shown.  When  this  switch  is  turned  about  one 
quarter  of  a  revolution  in  either  direction,  one  end  will  ride  over 
the  upper  contact  and  the  other  one  over  the  lower  contact. 
The  reversing  drum  and  switch  M  are  mounted  on  the  same 
spindle  and  move  together.  They  are  located  within  the  con- 
troller box,  on  top  of  the  motor,  and  are  moved  by  the  horizontal 
bar ;  see  Fig.  326.  The  shaded  portions  of  the  drum,  on  which  the 
brushes  h  and  i  rest  are  made  of  insulating  material  so  that  when 
switch  M  and  the  reversing  drum  are  in  the  position  shown  the 
motor  circuit  is  open  at  two  points.  This  is  the  position  of  these 
parts  when  the  machine  is  stopped. 

The  starting  resistance  is  shown  above  the  reversing  drum, 
and  in  the  machine  it  occupies  the  space  at  the  back  of  the  con- 
troller box,  shown  on  top  of  the  motor  in  Fig.  326.  The  segment 
R  is  a  series  of  contacts  that  are  connected  with  the  resist- 
ance in  the  resistance  box;  No.  2  contact  being  con- 
nected with  point  2  on  the  resistance  and  so  on  for  all  the  other 
numbers.  The  switch  arm  JVis  moved  over  the  contacts  R  by  a 
magnet  that  is  represented  by  the  spiral  L.  The  motor  arma- 
ture and  the  shunt  and  series  field  coils  are  shown  at  the  bottom 
of  the  diagram.  The  motor  is  compound  wound,  it  being  made 
so  for  the  purpose  of  keeping  the  starting  current  as  low  as  possi- 
ble. The  path  of  the  current  through  the  wires  is  as  follows :  Sup- 
pose the  reversing  drum  andtheJtf  switch  are  revolved  in  the  direc- 
tion in  which  the  hands  of  a  clock  move,  then  brushes #  and  i  will 
rest  on  one  segment,  and  h  and  Jc  will  rest  on  the  other  segment. 


736  HANDBOOK   ON    ENGINEERING. 

As  switch  M  will  now  be  closed,  the  current  will  flow  to  brush 
g  and  through  the  reversing  drum  segment  to  brush  i;  then  it 
will  follow  the  wire  to  the  right  side  /  of  the  armature  and  pass- 
ing through  the  latter  will  reach  wire  E  and  thus  brush  h,  from 
which  it  will  pass  to  brush  Jc.  From  this  brush  the  current  will 
go  to  and  through  magnet  L  and  by  wire  C '  and  switch  N  will 
reach  contact  No.  10.  As  this  contact  is  connected  with  point 
10  of  the  resistance  the  current  will  reach  the  latter  and  will  pass 
through  the  whole  of  it,  coming  out  at  the  opposite  end  C.  This 
end  is  connected  with  contact  (7,  so  that  from  this  segment  the 
current  can  flow  through  wire  0  to  the  end  F  of  the  series  field 
coils,  and  passing  through  these  to  end  H,  will  find  its  way  to 
wire  /,  and  thus  return  to  the  opposite  side  of  the  main  line. 
From  this  explanation  it  will  be  seen  that  the  current  will  pass 
through  the  motor  armature,  and  then  through  the  whole  of  the 
resistance  in  the  resistance  box,  and  then  through  the  series  field 
coils,  and  finally  reach  the  other  side  of  the  main  line.  From 
the  switch  M  another  current  will  branch  off  and  run  to  binding 
post  .D,  and  thence  through  the  shunt  field  coil .  to  binding  post 
.fiT and  thus  to  wire/,  and  through  the  latter  to  the  opposite  of 
the  main  line. 

The  switch  lever  N  is  in  some  cases  arranged  so  that  the  mag- 
net L  acts  to  hold  it  upon  contact  10  and  a  spring  acts  to  carry 
it  forward  toward  contact^.;  in  other  cases  the  magnet  is  wound 
with  two  coils,  one  of  which  pulls  N  in  one  direction  and  the 
other  pulls  it  in  the  opposite  direction,  the  two  coils  being  so  pro- 
portioned that  N  moves  gradually  from  contact  10  toward  con- 
tact A.  If  we  take  the  spring  arrangement,  then  magnet  L  will 
pull  N  back  toward  contact  10,  and  the  spring  will  pull  it  forward. 
As  the  starting  current  is  very  strong,  ^Twill  be  held  on  contact 
10,  but  as  the  current  weakens,  the  spring  will  begin  to  overpower 
the  magnet,  and  N  will  slide  over  contact  9  and  then  8  and  7  and 
so  on  to  contact  A.  As  contact  9  is  connected  with  the  point  9 


HANDBOOK    ON    ENGINEERING.  737 

of  the  resistance,  when  JV  reaches  it,  the  section  of  the  resistance 
between  points  10  and  9  will  be  cut  out.  When  N  reaches  con- 
tact 7  the  resistance  between  points  10  and  7  will  be  cut  out  for 
the  latter  point  is  connected  with  contact  7.  As  all  the  contacts 
are  connected  with  the  corresponding  points  of  the  resistance, 
when  N  reaches  contact  (7,  all  the  resistance  in  the  resistance  box 
will  be  cut  out  of  the  circuit.  As  will  be  noticed,  contact  B  is 
connected  with  the  center  point  G  of  the  series  field  coil  so  that 
when  N  reaches  contact  B  one-half  of  the  series  coils  will  be  cut 
out  in  addition  to  the  whole  of  the  resistance  box.  When  N 
reaches  contact^  the  current  will  pass  directly  to  wire/,  and  thus 
cut  out  all  the  series  field  coils  and  then  the  motor  will  run  as  a 
plain  shunt-wound  machine,  and  its  speed  will  be  the  highest  it 
can  attain. 

If  the  reversing  drum  and  switch  M  are  now  revolved  to  the 
position  shown  in  the  diagram,  the  circuit  through  the  motor  will 
be  broken  and  the  machine  will  come  to  a  state  of  rest.  If  the 
reversing  drum  and  M  are  now  revolved  in  the  opposite  direction, 
that  is,  contrary  to  the  movement  of  the  hands  of  a  clock,  the 
brushes  g  and  h  will  rest  on  one  of  the  revolving  drum  segments, 
and  i  and  k  on  the  other  segment.  If  the  path  of  the  current  is 
now  traced  it  will  be  found  that  it  will  enter  the  armature  through 
wire  E,  and  the  left  side,  instead  of  through  wire  7,  as  in  the  pre- 
vious case.  It  will  also  be  found,  however,  that 'the  current  after 
passing  through  the  armature  will  reach  the  series  field  coils 
through  Fj  which  is  the  same  path  as  before,  so  that  the  direction 
of  the  current  has  been  reversed  through  the  armature  only, 
which  is  what  is  required  to  reverse  the  direction  of  rotation  of 
the  motor.  Whichever  way  the  switch  M  and  the  reversing  drum 
are  turned,  the  direction  of  the  currents  through  the  series  field 
coils  and  the  shunt  field  coil  will  be  the  same,  and  only  the  arma- 
ture current  will  be  reversed. 

Cutting  out  the  series  field  coils  not  only  increases  the  speed 

47 


738  HANDBOOK   ON    ENGINEERING. 

of  the  motor,  but  obviates  the  danger  of  the  car  attaining  a  dan- 
gerously high  speed  if  the  load  is  being  lowered.  A  shunt  wound 
motor  will  run  as  a  motor  up  to  a  certain  speed,  but  if  the  veloc- 
ity is  forced  above  this  point  by  driving  the  machine  by  the  ap- 
plication of  external  power,  then  the  motor  will  begin  to  act  as  a 
generator,  and  as  it  takes  power  to  run  a  generator  the  motor  will 
begin  to  hold  back.  Now  if  an  elevator  car  is  running  down 
with  a  heavy  load,  the  load  will  draw  the  car  down,  and  unless  a 
resistance  of  some  kind  is  interposed,  the  speed  will  become 
preater  and  greater  as  the  car  descends,  and  by  the  time  it 
reaches  the  bottom  of  the  shaft  it  may  be  running  at  a  velocity 
almost  equal  to  that  attained  by  a  free  fall.  The  power  required 
to  drive  the  motor  when  acting  as  a  generator  serves  to  hold  the 
car  back,  for  the  current  developed  increases  very  rapidly  with 
increase  of  speed,  so  that  an  increase  of  speed  of  ten  or  fifteen 
per  cent  above  the  normal  running  velocity  will  be  about  as  much 
as  can  be  reached  even  with  an  extra  heavy  load. 

Although  the  motor  will  act  as  a  generator  and  hold  the  car  so 
that  it  cannot  attain  a  dangerous  speed  when  descending  under 
the  influence  of  a  heavy  load,  it  will  only  accomplish  this  result 
when  the  circuit  is  closed  ;  for  if  the  circuit  is  open  there  will  be 
no  power  generated ;  hence,  no  power  will  be  absorbed  by  the 
motor.  As  can  be  readily  seen,  it  is  possible  for  the  circuit  out- 
side of  the  motor  to  become  broken  by  the  melting  of  a  fuse  or 
some  other  cause,  and  if  this  occurs  when  the  car  is  coming  down 
with  a  heavy  load  there  might  be  a  serious  accident.  To  obviate 
such  mishaps  the  main  switch  is  made  with  a  magnet  &,  which 
holds  the  switch  closed  so  long  as  current  passes  through  it,  but 
allows  the  switch  to  swing  open  if  the  line  current  disappears. 
This  switch  on  this  account  is  called  a  potential  switch,  because 
it  is  arranged  to  be  actuated  by  the  difference  of  potential  be- 
tween the  two  sides  of  the  line.  When  the  line  current  fails,  and 
the  potential  switch  opens,  the  blade  m  comes  into  contact  with  w 


HANDBOOK   ON    ENGINEERING.  739 

and  thus  the  circuit  for  the  motor  armature  is  closed  through  the 
resistance  wire  s,  which  is  connected  with  contact  7.  This  con- 
nection short  circuits  the  armature  through  a  resistance  sufficient 
to  keep  it  from  being  burned  out,  but  not  enough  to  prevent  the 
motor  from  acting  as  a  brake  and  holding  the  car  down  to  a  safe 
speed. 

The  wire  c  c,  which  runs  from  magnet  b  of  the  potental  switch 
it  will  be  noticed,  connects  with  a  coil  marked  safety  brake  mag- 
net. This  magnet  acts  normally  to  hold  the  brake  off  when  the 
machine  is  running,  but  if  the  current  passing  through  it  dies  out, 
then  it  acts  to  put  the  brake  on.  Now,  as  has  already  been  ex- 
plained, when  the  current  is  flowing  in  the  main  line,  there  is  a 
current  passing  through  coil  b  of  the  potential  switch ;  hence, 
there  is  a  current  passing  through  the  coil  of  the  safety  magnet  for 
the  brake ;  but  if  the  line  current  fails  the  current  through  the 
brake  magnet  will  also  fail  and  the  brake  will  go  on  ;  so  that  the 
car  will  be  doubly  protected,  one  protection  being  the  short  cir- 
cuiting of  the  motor  circuit  through  wire  s,  and  the  other  the  ap- 
plying of  the  brake  by  reason  of  the  failure  of  the  current  to  flow 
through  the  safety  brake  magnet. 

As  to  directions  for  the  proper  care  of  these  machines,  very 
little  need  be  said,  as  they  are  simple  and  substantial  in  con- 
struction and  give  very  little  trouble.  The  motor  proper  requires 
the  same  attention  as  is  given  to  any  stationary -motor,  that  is, 
the  commutator  and  all  other  parts  must  be  kept  as  clean  as  pos- 
sible and  the  brushes  must  be  properly  set.  As  to  the  other 
parts,  all  that  need  be  said  is  that  the  bearings  must  be  well  lubri- 
cated and  free  from  grit.  They  must  be  tight  enough  to  not  al- 
low the  parts  to  play,  but  at  the  same  time  care  must  be  taken 
that  they  are  not  so  tight  as  to  heat  up  or  cut.  All  bolts  and 
nuts  must  be  regularly  examined  and  kept  tight,  so  that  they 
may  not  work  loose  or  out  of  place.  The  most  important  point 
to  observe,  however,  is  not  to  undertake  under  any  circumstances 


740  HANDBOOK    ON    ENGINEERING. 

to  tinker  with  the  sheave  wheel  and  the  gears  that  connect  it  with 
the  horizontal  bar  that  operates  the  brake  and  controller 
switches.  Neither  must  the  brake  or  the  switches  be  disturbed. 
All  that  is  to  be  done  to  the  latter  is  to  keep  the  contacts  bright 
and  clean.  If  any  of  these  parts,  from  the  sheave  wheel  to  the 
controller  switches,  get  out  of  set,  so  that  the  machine  will  not 
run  satisfactorily,  do  not  undertake  to  readjust  them,  but  send 
for  an  expert  from  the  elevator  company.  If  any  of  these  parts 
are  removed  or  shifted  there  is  danger  of  their  not  being  put 
back  in  their  proper  position,  and  if  they  are  misplaced  a  very 
serious  accident  may  be  the  result.  If  the  proper  adjustment  of 
these  parts  is  destroyed,  the  elevator  will  not  stop  automatically 
at  the  top  and  bottom  landings,  but  will  run  too  far  at  one  end 
and  stop  short  of  the  mark  at  the  other ;  hence,  the  car  may 
either  strike  violently  against  the  floor  or  ran  at  full  speed  into 
the  overhead  beams,  and  in  either  case  the  results  might  be  very 
serious.  Even  elevator  experts  have  to  go  cautiously  in  adjust- 
ing the  position  of  the  sheave  wheel  and  the  parts  connected 
with  it. 

The  fact  that  those  not  thoroughly  posted  in  the  operation  of 
these  elevators  should  not  tamper  with  the  hand  rope  sheave  and 
its  connections,  is  not  at  all  unfortunate,  for  it  is  next  to  impos- 
sible for  them  to  get  out  of  place ;  but  special  caution  is  advised 
at  this  point,  because  there  are  many  men  who  are  apt  to  take  it 
for  granted  that  if  the  machine  runs  poorly  from  some  trifling 
cause  that  they  have  not  been  able  to  locate,  the  trouble  must  be 
due  to  some  defect  in  the  adjustment  of  the  several  parts  of  the 
operating  sheave  and  its  connections.  They  will  then  proceed  to 
pull  the  machine  apart,  and  when  they  put  it  together  again  they 
are  very  liable  to  get  it  connected  wrong,  and  if  such  should  be 
the  case  the  first  trip  made  by  the  elevator  might  end  seriously. 

Although  the  machine  described  in  the  foregoing  works  in  an 
entirely  satisfactory  manner,  it  has  been  superseded  almost  en- 


HANDBOOK   ON    ENGINEERING. 


741 


tirely  in  first-class  installations  of  recent  date  by  machines  that 
are  controlled  by  means  of  a  small  switch  in  the  car  instead  of 
the  hand  rope.  There  are  several  types  of  such  elevators  made 
by  the  Otis  company,  one  of  the  latest  designs  being  shown  in 
Fig.  328. 


w 


Fig.  328.    Latest  design  of  direct  connected  machine. 

As  will  be  noticed  at  once,  this  machine  is  different  in  several 
respects  from" the  hand  rope  control  machine  shown  in  Fig.  326 .  As 
the  machine  is  controlled  by  the  movement  of  a  switch  in  the  car, 
the  brake  cannot  very  well  be  actuated  mechanically,  hence  a 
magnetic  brake  is  provided,  the  magnet  being  seen  at  the  top  of 
-the  stand  to  the  right  of  the  motor.  The  automatic  stopping  de- 
vices and  the  slack  cable  stop  are  also  arranged  so  as  to  act  upon 


742 


HANDBOOK    ON    ENGINEERING. 


switches,  which  are  contained  within  the  casings  seen  at  the  front 
end  of  the  hoisting  drum.  The  controller  for  this  type  of 
machine  is  not  placed  on  top  of  the  motor,  generally,  for  since  it 


CAff 


Fig.  329.    Diagram  of  wiring  connections  for  controller. 

is  not  connected  mechanically  with  any  of  the  moving  parts  of  the 
machine,  it  can  be  located  at  any  convenient  point,  and  is  then 
connected  with  the  motor  armature,  field  coils  and  with  the  brake 


HANDBOOK    ON    ENGINEERING.  743 

magnet  and  automatic  stop  switches  by  means  of  copper  wires. 
The  controller  used  with  this  type  of  machine  is  arranged  after 
the  fashion  of  a  switchboard,  the  switches  being  located  on  the 
front,  and  the  connecting  wires,  together  with  the  starting  resist- 
ance, being  at  the  back.  The  switches  are  actuated  by  means  of 
electromagnets,  and  on  that  account  the  device  is  called  a  magnet 
controller.  The  diagram  of  the  wiring  connections  with  this  con- 
troller is  more  complicated  than  that  for  the  hand  rope  controller, 
but  for  the  purpose  of  simplifying  the  drawing  as  much  as  pos- 
sible we  have  removed  all  the  connections  that  are  not  actually 
necessary  for  a  proper  understanding  of  the  general  arrangement 
of  the  circuits.  This  simplified  diagram  is  shown  in  Fig.  329. 

The  front  of  the  controller  is  shown  in  Fig.  330,  and  the  back 
of  same  in  Fig.  331,  the  starting  resistance  being  removed  in  this 
illustration  so  as  to  afford  a  clear  view  of  the  wire  connections. 
The  side  of  the  starting  resistance  can  be  seen  in  Fig.  330.  In 
this  last  named  illustration,  all  the  switches  are  in  the  position 
they  take  when  the  elevator  is  stopped.  The  two  large  switches 
on  either  side  at  the  bottom  of  the  board  are  the  starting  switches, 
one  acting  to  run  the  car  up  and  the  other  one  to  run  it  down. 
The  two  smaller  switches  occupying  the  center  of  the  bottom 
panel  of  the  board  and  the  two  switches  in  the  upper  corner  are 
for  the  purpose  of  accelerating  the  velocity  of  the  motor  when  it 
is  started.  When  the  motor  starts,  there  is  a  resistance  in  the 
armature  circuit,  and  the  current  after  passing  through  the  arma- 
ture is  passed  through  series  field  coils.  After  the  motor  has 
started,  the  starting  resistance  is  cut  out,  and  then  the  series  field 
coils  are  cut  out,  so  that  when  the  full  speed  is  attained,  the 
motor  is  a  simple  shunt- wound  machine.  In  this  respect  the 
arrangement  of  the  motor  circuits  is  the  same  as  in  the  hand  rope 
controller  machine. 

When  it  is  desired  to  start  the  car,  a  small  switch  in  the  latter 
is  moved  toward  the  right  or  left,  according  to  the  direction  in 


744 


HANDBOOK    ON    ENGINEERING. 


which  the  car  is  to  move.  To  run  the  car  up,  the  car  switch  is 
turned  to  the  left,  and  this  movement  sends  a  current  through  the 
magnet  of  the  lower  right  side  magnet  on  the  controller  board. 


Fig.  330.    Showing  front  of  controller. 

This  magnet  then  lifts  its  plunger  and  the  two  discs  mounted  upon 
the  latter  come  into  contact  with  the  stationary  connectors  located 
just  above  them,  and  then  the  current  can  find  its  way  through 


HANDBOOK    ON    ENGINEERING  „ 


745 


the  motor  circuits  in  the  proper  direction  to  produce  the  upward 
motion.  The  four  small  switch  magnets  on  the  controller  board 
are  connected  in  separate  circuits  that  are  in  parallel  with  each 


Fig.  881.    Back  ot  controller. 

other,  and  in  shunt  relation  to  the  armature  of  the  motor.  When 
the  motor  first  starts,  the  counter  electromotive  force  developed 
by  the  armature  is  not  as  great  as  when  it  is  running  at  full  speed, 


746  HANDBOOK    ON    ENGINEERING,, 


HANDBOOK   ON   ENGINEERING.  74? 

ping  the  motor,  if  the  car  reaches  either  end  of  its  travel  without 
being  stopped  by  the  operator,  or  the  action  of  the  stop  motion 
switch.  This  switch  is  closed  under  ordinary  conditions,  so  that 
the  current  in  wire  C  can  flow  all  the  way  to  the  lower  contact  a 
of  the  car  switch.  If  it  is  desired  to  run  the  car  down,  the  car 
switch  is  turned  to  the  right,  and  then  wire  G  is  connected  with 
wires  D '  and  FD.  The  stop  motion  switch  is  normally  in  the 
position  shown  so  that  the  current  in  wire  D '  can  pass  to  D0  and 
following  this  wire  it  will  reach  contact  DO  which  is  under  the 
lower  disc  of  the  right  side  starting  switch.  Through  the  disc 
this  contact  is  connected  with  the  corresponding  contact  on  the 
other  side  of  the  disc,  and  this  latter  contact  is  connected  with  a 
wire  that  carries  the  current  to  the  magnet  of  the  left  side  starting 
switch.  Considering  now  the  main  current  in  the  +  line  it  can 
be  seen  that  it  can  flow  down  to  the  line  near  the  bottom  of  the 
controller  portion  of  the  diagram,  and  which  terminated  in  the 
-f-  contacts  of  both  the  starting  switches,  but  can  go  no  further 
so  long  as  the  discs  on  the  plungers  of  the  magnets  are  in  the 
lower  position.  As  soon,  however,  as  the  current  coming  from 
the  car  switch  passes  through  the  magnet  of  the  left  side  switch, 
as  just  explained,  the  plunger  will  be  lifted,  and  then  the  disc  will 
connect  the  +  contact  with  the  S2  contact,  and  also  with  a 
smaller  contact  B.  When  this  connection  is  made,  the  main  cur- 
rent can  flow  from  contact  S2  to  contact  82  of  the  right  side 
switch,  and  thence  through  the  connecting  disc  to  contact  I  which 
is  connected  by  wire  to  binding  post  I;  the  latter  being  con- 
nected with  the  right  side  armature  terminal  I.  After  passing 
through  the  armature  the  main  current  reaches  binding  post  E 
and  through  the  connecting  wire  the  contact  E  at  the  top  of  the 
left  side  starting  switch,  and  as  the  plunger  of  this  switch  is  in 
the  raised  position,  the  current  can  pass  to  contact  R  and  thus 
reach  the  upper  end  R  of  the  starting  resistance  in  the  resistance 
box. 


748  HANDBOOK    ON    ENGINEERING. 


HANDBOOK   ON    ENGINEERING.  749 

Thus  it  will  be  seen  that  the  four  switches,  1,2,  3  and  4,  will 
act  one  after  the  other.  This  same  operation  is  repeated  if  the 
car  switch  is  moved  to  the  right,  so  as  to  run  the  elevator  down, 
the  only  difference  being  that  the  starting  switch  at  the  right  side 
of  the  board  will  be  lifted,  but  the  action  of  the  four  smaller 
switches  will  be  the  same. 

In  addition  to  the  operating  circuits  described  in  the  foregoing 
there  are  wires  that  connect  the  slack  cable  switch  with  the  motor 
circuits  and  other  connections  by  means  of  which  the  elevator  may 
be  run  from  the  controller  board  whenever  desired.  These  con- 
nections are  not  shown  in  Fig.  329,  as  they  would  complicate  the 
drawing,  and  it  is  not  thought  advisable  to  complicate  the  explan- 
ation of  the  main  part  of  the  system  for  the  sake  of  introducing 
the  minor  details. 

This  type  of  electric  control  is  used  for  elevator  machines  in- 
stalled in  office  buildings ,  and  others  placed  where  the  car  is  oper- 
ated by  a  regular  attendant.  For  private  house  elevators  and  for 
dumb  waiters  it  is  necessary  to  modify  the  controlling  system  so 
that  the  car  may  be  operated  not  only  from  within,  but  also  from 
any  of  the  floors  of  the  building.  It  is  further  necessary  that 
the  circuit  connections  be  such  that  if  the  car  is  operated  from 
any  floor,  it  will  run  to  that  floor,  whether  above  or  below  it,  and 
further,  so  that  if  it  is  being  operated  by  a  person  within  the  car 
it  cannot  be  operated  by  any  one  else  from  any  of  the  landings. 
It  must  also  be  arranged  so  that  if  the  car  is  set  in  motion  from 
any  floor  it  cannot  be  stopped  or  interfered  with  in  any  way  by 
a  person  at  another  floor.  For  the  purpose  of  safety  the  system 
must  also  be  arranged  so  that  the  car  cannot  move  away  from  any 
floor  until  the  landing  door  is  closed.  This  feature  is  necessary 
to  guard  against  people  falling  through  the  open  doorway  into  the 
elevator  shaft.  Although  it  would  appear  difficult  to  accomplish 
all  these  results  without  resorting  to  great  complications,  as  a 
matter  of  fact  the  system  used  by  the  Otis  company  is  decidedly 


750 


HANDBOOK    ON    ENGINEERING. 


HANDBOOK   ON    ENGINEERING.  751 

simple.  At  each  floor  of  the  building  a  push  button  is  placed, 
and  by  pressing  this  for  an  instant  the  car  is  set  in  motion  wher- 
ever it  may  be,  providing  it  is  not  being  used  by  some  other  per- 
son, and  when  it  reaches  the  floor  from  which  it  has  been  operated 
it  will  stop  automatically.  If  the  elevator  is  operated  from  the 
car,  a  button  is  pushed  that  corresponds  to  the  floor  at  which  it 
is  desired  to  stop,  the  car  will  then  begin  to  move,  and  when  the 
floor  is  reached  it  will  stop.  If  the  passenger  after  stepping  out 
of  the  car  forgets  to  close  the  landing  door,  the  elevator  cannot 
be  moved  away  from  the  landing  by  the  manipulation  of  any  of 
the  push  buttons  on  the  various  floors  or  within  the  car.  The 
way  in  which  all  these  results  are  accomplished  can  be  made 
clear  by  the  aid  of  Fig.  332,  which  is  a  simplified  diagram  of  the 
wiring. 

In  this  diagram  most  of  the  parts  are  marked  with  their  full 
name.  The  floor  controller  is  a  drum,  which  is  revolved  by  the 
elevator  machine,  and  its  office  is  to  shift  the  connections  of  the 
wires  11,  22,  33,  44,  from  one  side  of  the  circuit  DU  to  the 
other  as  the  car  ascends  and  descends  in  the  elevator  shaft.  This 
shifting  of  these  connections  is  necessary  to  cause  the  car  to  run 
down  if  above  the  landing  from  which  it  is  operated,  and  to  run 
up  if  it  is  below  the  landing.  The  actual  position  of  the  floor  con- 
troller with  reference  to  the  elevator  machine  can  be  seen  in  Fig. 
333  in  which  the  floor  controller  is  located  back  of  the  motor  and  is 
driven  from  the  drum  shaft  by  means  of  a  chain  and  sprocket  wheel. 
In  the  diagram  Fig.  332  it  will  be  noticed  that  the  drum  surface  is 
divided  into  two  segments  and  upon  one  rests  the  brush  of  wire 
D  while  upon  the  other  rests  the  brush  of  wire  U.  The  twelve 
contacts  shown  at  G  form  the  operating  switch.  The  center  row 
marked  m  n  o  p  are  movable,  and  the  four  contacts  above  them 
as  well  as  the  four  below  are  stationary.  The  center  row  of  con- 
tacts m  n  o  p  are  moved  upward  by  a  magnet  represented  by  the 
coil  D  and  they  are  moved  downward  by  another  magnet  repre- 


752  HANDBOOK   ON    ENGINEERING. 

sented  by  the  coil  V.  From  this  it  will  be  seen  that  if  a  current 
comes  from  the  floor  controller  through  wire  D  the  movable  con- 
tacts of  G  will  be  lifted  and  will  connect  with  the  top  row,  while 
if  the  current  comes  from  the  floor  controller  through  wire  (7,  the 
movable  contacts  will  be  depressed  and  will  make  connections  with 
the  lower  row  of  contacts. 

The  main  switch  that  connects  the  motor  circuits  with  the 
main  line  is  shown  at  S.  As  will  be  noticed,  a  wire  marked  d  +  H 
runs  from  the  +  wire  to  the  right  side  of  the  diagram,  where  the 
landing  and  the  car  push  buttons  and  their  connections  are  shown. 
This  wire  runs  from  top  to  bottom  of  the  elevator  shaft  and  is  con- 
nected with  switches  that  are  closed  when  the  landing  doors  are 
closed,  and  open  when  the  doors  are  open.  These  switches  are 
indicated  by  the  four  circles  marked  door  contacts,  the  diagram 
being  for  a  building  four  stories  high.  If  the  door  contacts  are 
closed,  the  current  can  pass  as  far  as  the  wire  marked  -f-  which 
runs  through  the  flexible  cable  to  the  car.  In  the  car  there  is  a 
switch  in  this  wire  and  further  on  a  gate  contact,  which  is  closed 
when  the  car  door  is  closed.  If  these  switches  are  closed,  the 
current  can  return  from  the  car  through  wire  A  and  run  as  far  as 
the  center  of  the  diagram  under  the  main  switch  S.  The  floor 
controller  is  shown  in  the  position  corresponding  to  the  car  at  the 
bottom  of  the  shaft.  Suppose  now  that  the  landing  push  button 
I  is  pressed  for  a  second,  then  the  wires  B  and  I  will  be  connected, 
and  the  current  in  wire  A  will  pass  to  wire  B  and  through  the 
push  button  to  wire  I  and  thence  to  wire  II.  The  coil  between 
wire  I  and  wire  II  is  a  magnet,  and  as  soon  as  the  current  passes 
through  it,  it  draws  the  contact  to  the  right  and  thus  provides  a 
path  for  the  current  direct  from  wire  A  to  wire  ZZ,  so  that  the  push 
button  may  be  raised  without  opening  the  circuit.  The  current 
in  wire  II  will  pass  through  the  floor  controller  to  wire  £7 and  thus 
through  magnet  U  of  the  operating  switch  G.  This  magnet  will 
then  draw  down  the  movable  contacts  m  n  o  p,  and  the  main  line 


HANDBOOK    ON    ENGINEERING. 


753 


current  from  the  -f-  wire  will  pass  from  contact  m  to  wire  m'  and 
through  wire  m'  to  point  zo,  hence  through  wire  wr  to  the  acceler- 
ating, or  starting  resistance,  and  to  wire  F  which  leads  to  tha 
series  field  coils.  Returning  from  these  coils  through  wire  H  to 
Eaagnet  switch  2  and  thence  wire  n'  to  contact  n,  and  as  this  con- 


Fig?.  333.    Direct  connected  eleyator  with  floor  controller. 

tact  is  pressing  against  the  one  directly  below  it,  the  current  will 
flow  through  the  connection  to  wire  E  and  thus  to  the  armature ; 
returning  from  the  latter  through  wire  I  and  wire  o'  to  the  contact 
below  o  and  thus  to  o  and  through  the  permanent  connection  to 
contact  p  and  to  the  lower  right  hand  contact,  which  is  connected 

48 


754  HANDBOOK    ON    ENGINEERING. 

with  wire  r,  which  runs  to  the  —  side  of  the  main  switch.  The 
shunt  field  current  is  derived  from  wire  m'  and  returns  to  contact 
p  and  thus  to  wire  r  through  wire  p* ',  as  can  be  clearly  traced. 
The  brake  magnet  current  starts  from  the  left  side  contact  of  G 
through  wire  +  B  and  returns  directly  to  the  lower  end  of 
wire  r. 

The  magnet  switches  1  and  2  act  in  the  same  manner  as  those 
in  diagram  Fig.  329,  that  is,  by  the  increase  in  the  counter  electro- 
motive force  of  the  armature  which  causes  the  current  that  passes 
through  them  to  increase  in  strength.  When  magnet  I  closes  its 
switch,  the  current  passes  from  wire  w9  to  wire  F  and  thus  the 
accelerating  resistance  is  cut  out.  When  magnet  2  closes  its 
switch  the  current  passes  from  wire  m"  directly  to  n'  and  thus  to 
the  armature  without  going  through  the  series  field  coils ;  thus 
the  latter  are  cut  out. 

Returning  now  to  the  operation  of  the  floor  controller  it  will  be 
seen  that  as  the  current  is  flowing  through  wire  II  the  circuit  will 
be  broken  if  the  controller  is  rotated  until  the  gap  at  the  top 
comes  under  the  brush  of  wire  II.  Now  the  floor  controller 
drum  begins  to  turn  as  soon  as  the  elevator  machine  moves,  and 
it  is  so  geared  to  the  elevator  drum  that  when  the  car  comes  op- 
posite the  first  floor  the  brush  of  wire  II  will  be  over  the  upper 
gap,  and  then  the  circuit  will  be  open  and  the  magnet  U  will  be 
de-energized  and  allow  switch  G  to  move  back  to  the  stop  position. 

If  button  No.  4  is  pressed  instead  of  No.  1  the  car  will  not 
stop  until  the  gap  at  the  top  of  the  floor  controller  drum  comes 
under  the  brush  wire  44,  for  the  circuit  between  this  wire  and 
wire  U  will  be  closed  until  that  position  is  reached. 

If  the  car  is  run  up  to  the  fourth  floor,  as  the  gap  at  the  top 
of  the  floor  controller  drum  will  then  be  under  the  brush  of  wire 
44,  the  brushes  of  wire  11,  22  and  33  will  rest  upon  the  same 
segment  as  the  brush  of  wire  D;  therefore,  if  with  the  car  at 
the  top  floor  a  button  is  pressed  at  any  one  of  the  lower  floors 


HANDBOOK    ON    ENGINEERING.  755 

the  current  will  pass  from  its  corresponding  wire  to  wire  D  and 
thus  through  magnet  coil  D  and  to  wire  /  and  wire  r.  The  cur- 
rent passing  through  magnet  D  will  draw  the  movable  contacts  of 
the  operating  switch  6  upward,  and  thus  set  the  elevator  machine 
in  motion  in  the  opposite  direction  from  that  in  which  it  runs  , 
when  the  IT  magnet  is  energized. 

In  tracing  out  the  circuits  from  the  floor  push  buttons  as  just 
explained  it  will  be  noticed  that  if  any  one  of  them  is  depressed, 
the  current  in  wire  A  will  flow  through  wire  B  to  the  button  de- 
pressed, and  then  enter  the  wire  returning  from  that  button. 
When  the  car  buttons  are  depressed  the  current  in  wire  A  will 
pass  to  wire  C  and  then  through  the  button  in  the  car  to  the 
proper  return  wire ;  that  is,  to  one  or  the  other  of  the  wires 
1,  2,  3,  4.  After  entering  one  of  these  four  wires  the  current 
follows  the  same  path  as  it  does  when  one  of  the  floor  buttons 
is  depressed.  The  magnet  B'  in  the  B  wire,  and  the 
magnet  C'  in  the  C  wire,  are  for  the  purpose  of  preventing  in- 
terference between  a  person  operating  the  elevator  from  within 
the  car  and  another  one  at  one  of  the  landings.  The  B'  switch  is 
actuated  by  a  magnet  that  is  wound  with  two  coils  that  act  in 
opposition  to  each  other.  These  coils  are  shown  to  the  left  of  B' '. 
When  the  elevator  is  operated  from  one  of  the  floor  push  buttons 
the  current  in  wire  A  passes  through  both  the  coils  on  the  magnet 
of  switch  Bf  and  as  one  coil  counteracts  the  other  the  switch 
is  left  closed  and  the  current  passes  directly  to  wire  B.  If  the 
elevator  is  operated  from  within  the  car  the  current  from  wire  A 
in  passing  to  wire  C  passes  through  one  of  the  coils  of  the  mag- 
net that  actuates  switch  B' ',  hence  this  switch  is  opened  and  the 
connection  with  wire  B  is  broken,  so  that  if  now  any  one  of  the 
floor  buttons  is  pressed  it  will  have  no  effect  as  the  circuit  is 
opened  at  switch  B'.  The  current  flowing  through  wire  C  passes 
through  a  magnet  that  acts  to  close  the  switch  C'  and  thus  allow 
a  portion  of  the  current  to  pass  directly  to  wire  r.  This  current 


756  HANDBOOK    ON    ENGINEERING. 

will  continue  to  flow  even  after  the  car  has  stopped  at  the  landing, 
providing  the  door  is  not  opened.  As  soon  as  the  door  in  the 
car,  or  the  landing  door,  is  opened  the  circuit  is  broken  either  in 
wire  Hor  in  wire  A,  and  then  the  car  cannot  be  moved  until  the 
doors  are  closed.  If  it  were  not  for  switch  (7  it  would  be  possi- 
ble for  a  person  at  one  end  of  the  landings  to  move  the  car  if  he 
pressed  the  button  during  the  short  interval  of  time  between  the 
stopping  of  the  car  and  the  opening  of  the  landing  door.  The 
opening  of  the  door  would  stop  the  car,  but  by  this  time  it  might 
be  a  foot  or  two  away  from  the  floor  level.  The  current  that 
passes  from  switch  C"  to  wire  r  is  kept  down  to  a  small  amount 
by  passing  it  through  a  high  resistance  which  in  the  diagram  is 
marked  700  w. 

The  electrical  portion  of  the  Otis  electric  elevators  has  been 
supplied  for  many  years  to  four  or  five  of  the  leading  companies, 
which  were  controlled  by  the  Otis,  and  during  the  last  two  or 
three  years  it  has  been  supplied  to  practically  all  the  prom- 
inent makers,  as  these  are  now  part  and  parcel  of  this 
company ;  hence  the  descriptions  given  in  the  foregoing 
are  more  than  likely  to  cover  any  case  met  with  in 
practice,  for  although  there  are  numerous  small  manufacturers, 
the  sum  total  of  their  elevators  in  use  is  comparatively  small. 
The  only  electric  elevators  in  addition  to  those  described  in  the 
foregoing  that  have  come  into  extensive  use  are  those  made  by  the 
Sprague  Electric  Co. 

These  machines  are  of  two  different  types,  one  being  the  ordi- 
nary drum  design,  and  the  other  the  screw  machine.  The  drum 
machine  is  similar  in  its  main  features  to  the  same  type  of  ma- 
chine of  other  makers,  and  it  is  only  in  the  minor  details  of  con- 
struction that  any  radical  difference  can  be  noted.  In  the  means 
employed  for  controlling  the  motion  of  the  motor,  however,  there 
is  a  decided  difference.  In  all  the  Sprague  elevators  the  car  is 
controlled  electrically,  hand  rope  control  not  being  used  in  any 


HANDBOOK   ON   ENGINEERING. 


757 


3 

<yf 

8 


I 

"» 


758  HANDBOOK    ON    ENGINEERING. 


HANDBOOK    ON    ENGINEERING. 


759 


Fig.  335.    Elevator  controller  board. 


760  HAND    BOOK    ON  ENGINEERING. 

The  nut  carried  by  the  traveling  cross- head  is  so  arranged  that 
when  the  latter  reaches  the  end  of  its  travels  at  either  end  of  the 
screw,  the  nut  is  released  and  then  rotates  with  the  screw  with- 
out moving  the  cross -head.  This  forms  a  perfect  top  and  bottom 
limit  stop,  for  even  if  the  motor  continues  to  run,  the  car  cannot 
be  carried  beyond  the  positions  corresponding  to  the  points  at 
which  the  nut  slips  around  in  the  cross-head. 

The  brake  for  holding  the  machine  is  mounted  upon  the  outer 
end  of  the  armature  shaft,  ancj.  can  be  seen  at  Fig.  334  at  the  ex- 
treme right  hand  side.  This  brake  is  actuated  by  a  magnet  that 
releases  it,  and  a  spring  that  throws  it  on.  When  the  current  is 
on,  the  brake  is  lifted  and  when  the  current  is  off  the  brake  goes 
on.  In  this  respect,  the  action  is  the  same  as  in  all  other  electric 
elevators. 

The  operation  of  the  motor  is  controlled  by  a  small  switch  in 
the  car,  which  is  connected  with  the  motor  circuits  by  means  of 
wires  contained  in  a  flexible  cable,  just  like  the  Otis  electrically 
controlled  machines.  The  controller  consists  of  a  main  switch, 
which  is  moved  by  a  small  motor  called  a  pilot  motor,  and  a  num- 
ber of  smaller  magnetic  switches  whose  action  will  be  presently 
explained.  All  these  parts  are  mounted  upon  a  switchboard,  and 
present  the  appearance  shown  in  Fig.  335.  The  pilot  motor  and 
main  switch  are  located  at  the  top  of  the  board,  and  the  magnet 
switches  cover  the  space  below,  while  the  starting  and  regulating 
resistance  is  mounted  on  the  back  of  the  board. 

The  complete  wiring  diagrams  for  these  machines  is  decidedly 
complicated  owing  to  the  fact  that  there  are  numerous  switches 
and  devices  whose  office  is  to  afford  additional  safety,  or  to  ren- 
der the  control  more  perfect.  When  all  the  parts  that  are  not 
actually  necessary  to  illustrate  the  system  are  removed,  however, 
the  diagram  becomes  quite  simple  and  can  be  readily  understood. 
Such  a  diagram  is  shown  in  Fig.  336.  This  diagram  shows  the 
motor  together  with  the  screw  and  sheaves,  the  elevator  car,  the 


HANDBOOK   ON   ENGINEERING.  761 

counterbalance,  and  the  operating  switches.  The  wires  marked  + 
and  —  are  connected  with  the  main  line.  The  switch  in  the  car 
is  connected  with  the  controller  by  means  of  four  wires,  marked 
c  b  d  and  s.  The  lower  one  of  these  wires,  marked  s,  is  connected 
with  the  stud  around  which  the  car  switch  swings.  When  the 
car  switch  is  moved  onto  the  upper  contact,  it  connects  wire  s 
with  wire  c  and  then  the  car  runs  up.  When  the  car  switch  is 
moved  down  onto  the  lower  contact,  wire  s  is  connected  with  wire 
d,  and  then  the  car  runs  down.  When  the  car  switch  is  placed  in 
the  central  position  wire  s  is  connected  with  wire  b  and  then  the 
elevator  stops.  The  two  switches  marked  "  up  limit,"  "  down 
limit,"  are  for  stopping  the  car  automatically  at  the  top  and  bot- 
tom landings.  Normally  the  up  limit  switch  is  closed  and  the 
down  limit  switch  is  open.  With  these  switches  in  this  position, 
which  is  the  position  in  which  they  are  shown  in  the  diagram,  the 
current  from  the  +  wire  can  pass  through  the  up  limit  switch  to 
wire  fc,  and  thence  through  wire  I  to  the  armature  of  the  motor, 
and  then  through  the  field  coils,  and  reach  wire  m.  It  cannot  go 
beyond  this  point  until  the  switch  C  is  moved.  This  is  the  main 
operating  switch,  which  in  Fig.  335  is  seen  at  the  top  of  the  board, 
the  contacts  being  arranged  in  two  circles.  The  pilot  motor  that 
rotates  the  arm  of  this  switch,  which  is  clearly  shown  in  Fig.  335,  is 
represented  in  this  diagram,  Fig.  336,  at  A.  As  will  be  seen  in 
this  diagram,  this  motor  has  a  field  provided  with  two  magnetizing 
coils,  one  for  the  up  motion,  and  one  for  the  down  motion,  and  in 
addition  it  is  provided  with  a  brake  to  stop  it  quickly  and  hold  it 
when  not  in  use.  The  portion  of  the  diagram  marked  B  is  the 
reversing  switch. 

Let  us  suppose  now  that  the  car  switch  is  moved  upward,  so  as 
to  cause  the  elevator  to  ascend,  then  wire  s  will  be  connected  with 
wire  c.  From  the  +  wire  a  current  will  pass  through  wire  a  to  s 
and  thus  to  c,  and  through  magnet  e  of  switch  ^,  thus  closing  this 
switch  so  as  to  connect  wires  li  and  i.  The  current  in  wire  c  will 


762 


HANDBOOK    ON    ENGINEERING. 


pass  to  B  and  through  the  connecting  plate  u  will  reach  the  end 
of  the  up  field  coil  of  the  pilot  motor,  and  then  pass  through  the 
armature  of  this  motor,  and  finally  through  the  magnet  that  re- 
leases the  brake.  The  pilot  motor  will  now  rotate  the  reversing 
switch  B  so  that  the  contact  plates  will  move  toward  the  left. 
This  movement  will  bring  plate  w  under  the  ends  of  wires  s  and  t, 
thus  permitting  a  current  from  s  to  pass  to  tf,  and  as  switch  g  is 


Fig.  886.    Diagram  of  elevator  controller  board. 

closed  this  current  will  reach  wire  h  and  thus  the  magnet  J, 
thereby  lifting  the  plunger  switch  that  closes  the  gap  between 
wire  q  and  the  —  wire.  As  the  arm  of  the  main  switch  0 
moves  with  the  reversing  switch  _B,  this  arm  will  ride  over  the 
contacts  on  the  right  side,  marked"  up  res."  and  thus  the  current 
from  wire  m  will  be  able  to  reach  wire  q  after  passing  through  the 
up  resistance. 


HANDBOOK    ON    ENGINEERING.  763 

If  sthe  car  switch  is  left  on  the  upper  contact,  the  pilot  motor 
will  continue  to  rotate  until  the  arm  of  switch  C  reaches  the  top 
of  the  resistance  contacts,  marked  Full  Up.  When  this  point  is 
reached,  the  contact  plate  u  of  the  reversing  switch  B  will  pass 
from  under  wire  c  and  the  terminal  of  the  up  field  of  the  pilot 
motor,  and  then  this  motor  will  stop  rotating. 

If  the  car  switch  is  not  kept  on  the  upper  contact  very  long, 
the  pilot  motor  can  be  stopped  with  the.  arm  of  switch  G  at  some 
intermediate  point  on  the  resistance  contacts,  thus  by  the  time 
during  which  the  car  switch  is  kept  upon  the  upper  contact,  the 
amount  of  resistance  cut  out  of  the  motor  circuit  can  be  con- 
trolled and  thereby  the  speed  of  the  car  can  be  controlled. 

In  this  operation  it  will  be  noticed  that  the  motor  is  connected 
with  the  main  line  and  that  the  current  enters  through  the  +  wire 
and  passes  out  through  the  —  wire.  If  now  we  turn  the  car 
switch  downward,  the  s  wire  will  be  connected  with  the  d  wire  and 
by  following  the  latter  to  the  reversing  switch  B  it  will  be  seen 
that  through  connecting  plate  v  it  is  connected  with  wire  z  which 
leads  to  the  end  of  the  down  field  of  the  pilot  motor,  thus  setting 
the  latter  in  motion  in  the  opposite  direction  so  as  to  shift  the 
contact  plates  of  B  toward  the  right,  and  at  the  same  time  rotate 
the  arm  of  the  main  switch  C  to  the  left,  thereby  making  contact 
with  the  contacts  of  the  down  resistance.  With  the  arm  of  G  in 
this  position,  it  will  be  seen  that  the  current  in  wire  I  can  flow 
through  the  motor  armature  and  field  and  through  wire  m  to  the 
arm  of  switch  G  and  through  the  down  resistance  to  wire  n  and 
thus  back  to  wire  Z,  thereby  forming  a  closed  circuit  within  the 
motor  wires  and  connections,  and  disconnected  from  the  main  line 
except  on  the  side  of  the  +  wire.  The  rotation  of  B  causes  the 
connecting  plate  x  to  ride  upon  the  terminals  of  wires  s  and  £,  and 
thus  a  current  is  sent  through  the  brake  magnet  so  as  to  lift  the 
brake,  and  allow  the  elevator  machine  to  run.  When  the  pilot 
motor  moves  the  arm  of  C  so  far  as  to  reach  the  top  of  the  down 


764  HANDBOOK   ON   ENGINEERING. 

resistance,  the  contact  plate  v  of  the  reversing  switch  B  will  pass 
beyond  the  terminals  of  wires  d  and  z,  thus  breaking  the  circuit 
of  the  pilot  motor  and  bringing  the  latter  to  a  stop. 

When  the  reversing;  switch  B  is  in  the  stop  position,  as  shown 
in  the  diagram,  the  terminal  of  wire  b  does  not  rest  upon  a  con- 
necting plate  but  when  the  switch  is  rotated  for  the  up  motion,  the 
terminal  of  b  rests  on  plate  v  so  that  if  the  car  switch  is  turned 
to  the  stop  position,  the  current  from  wire  b  will  pass  to  wire 
z  and  thus  reverse  the  direction  of  rotation  of  the  pilot 
motor,  and  return  the  switches  to  the  stop  position.  If 
the  car  is  running  down,  when  the  car  switch  is  turned 
to  the  stop  position,  the  current  from  wire  b  will  pass  to 
wire  z  and  thus  reverse  the  direction  of  rotation  of  the  pilot 
motor,  and  return  the  switches  to  the  stop  position.  If  the  car 
is  running  down,  when  the  car  switch  is  turned  to  the  stop  posi- 
tion, the  wire  b  will  ride  over  the  plate  u  and  thus  the  current 
will  pass  through  the  pilot  motor  through  the  up  field  and  thus 
rotate  the  switches  back  to  the  stop  position.  In  each  case,  as 
will  be  noticed,  whenever  the  current  flows  through  wire  b  it  ene 
gizes  coil  /  and  thus  opens  switch  g.  When  the  car  is  running 
up  the  current  for  the  brake  magnet  passes  from  wire  i  through 
the  switch  which  is  energized  by  the  main  current  flowing  in  wire  q. 
When  the  car  runs  too  far  down,  and  closes  the  down  limit  switch, 
the  motor  circuit  becomes  closed  through  wires  j),  r  and  &,  thus 
giving  another  path  for  the  current  generated  by  the  motor  arma- 
ture and  thereby  increasing  the  resistance  to  rotation. 

The  controller  for  the  Sprague  drum  machines  is  very  similar 
to  the  one  just  described.  It  is  operated  by  a  pilot  motor,  and 
in  so  far  as  the  controller  switchboard  is  concerned  looks  the 
same.  The  only  difference  is  that  rendered  necessary  by  the 
fact  that  in  lowering  as  well  as  in  raising  the  load,  the  motor  is 
connected  with  the  line.  This  requires  a  slight  change  in  some 
of  the  wire  connections. 


HANDBOOK    ON    ENGINEERING.  765 

The  electrical  parts  of  the  Sprague  elevators  require  very  little 
attention  other  than  to  keep  them  clean  and  all  the  contacts  bright 
and  in  proper  adjustment,  so  that  when  moved  a  good  contact 
may  be  made.  Of  the  mechanical  portion,  the  drum  machines 
require  about  the  same  attention  as  other  machines  of  this  type. 
As  to  the  screw  machines,  the  part  that  requires  most  attention  is 
the  screw  and  the  nut.  As  can  be  readily  understood,  if  the  nut 
were  solid,  the  friction  against  the  screw  would  be  very  great ; 
therefore,  to  reduce  this  friction,  the  nut  is  made  so  as  to  carry  a 
large  number  of  friction  balls.  These  run  in  a  groove  cut  in  the 
side  of  a  thread  and  roll  between  the  thread  and  the  screw  and 
the  thread  in  the  nut.  A  tube  is  attached  to  the  nut  to  provide  a 
path  through  which  the  friction  balls  can  pass  from  the  end  of  the 
thread  to  the  beginning,  thus  making  an  endless  path  in  which 
they  move.  As  these  friction  balls  are  subjected  to  a  heavy  pres- 
sure, there  is  more  or  less  danger  of  their  giving  trouble  and  on 
that  account  the  thread  on  the  screw  should  be  carefully  examined 
and  kept  as  clean  and  free  from  grit  as  possible.  Under  favorable 
conditions  these  screws  run  very  well,  the  wear  being  trifling,  but 
in  some  instances  they  are  liable  to  cut  badly,  hence  they  should 
be  closely  watched. 


DIRECTIONS  FOR  THE  CARE  AND  OPERATION  OF  THE 
ELECTRIC  ELEVATOR. 

Whenever  the  attendant  wishes  to  handle  the  machine  to  clean, 
adjust,  repair  or  oil  it,  he  should  see  that  the  current  is  shut  off 
at  the  switch,  and  thus  prevent  all  possibility  of  accident. 

Cleaning.  —  Keep  the  entire  machine  clean.  Clean  the  com- 
mutator and  other  contacts  and  brushes  carefully  with  a  clean 
cloth  and  keep  them  free  from  grease  and  dirt.  If  the  face  of  the 
rheostat  on  which  the  rheostat  arm  brushes  work  becomes  burnt, 
clean  with  a  piece  of  fine  sand-paper  (No.  0),  or  if  necessary  use 


HANDBOOK    ON    ENGINEERING. 


HANDBOOK    ON    ENGINEERING.  767 

resistance  is  cut  out  of  the  armature  circuit  by  slightly  easing  off 
the  weight,  which  acts  in  opposition  to  the  core  of  the  small 
solenoid.  This  solenoid  controls  a  valve  in  the  dash-pot  and 
thereby  regulates  its  speed  in  proportion  to  the  current  passing. 
If  a  governor  starter  is  used  and  the  current  is  admitted  too 
rapidly,  tighten  the  governor  spring  on  the  armature  shaft,  or 
close  the  vent  in  air  dash-pot.  If  the  car  refuses  to  ascend 
with  a  heavy  load,  immediately  throw  the  lever  to  the  center 
and  reduce  the  load,  as  in  all  probability  it  is  greater  than 
the  capacity  of  the  elevator.  If  it  refuses  to  ascend  with 
a  light  load,  throw  the  lever  to  the  center  and  have  the 
fusible  strip  examined.  If,  in  descending,  the  car  should 
stop,  throw  the  lever  to  the  center  and  examine  safeties, 
fusible  strip  and  machine,  and  before  starting,  be  sure  that  the 
cables  have  not  jumped  from  their  right  grooves.  If  the  car 
refuses  to  move  in  either  direction,  throw  the  lever  on  the  center 
and  have  the  fusible  strips  examined.  Never  leave  the  car  with- 
out throwing  the  lever  to  the  center.  If  the  car  should  be  stalled 
between  floors,  it  can  be  either  raised  or  lowered  by  raising  the 
brake  and  running  it  by  turning  the  brake-wheel  by  hand.  Such 
a  stoppage  might  be  caused  by  the  current  being  shut  off  at  the 
station,  undue  friction  in  the  machine,  too  heavy  a  load,  fuses 
burnt  out,  or  a  bad  contact  of  the  switches,  binding  posts  or  elec- 
trical connections.  If  the  car  by  any  derangement  of  cables  or 
switch  cannot  be  stopped,  let  it  make  its  full  trip,  as  the  auto- 
matic stop  will  take  care  of  it  at  either  end  of  the  travel.  The 
bearings  should  be  examined  occasionally  to  insure  no  heating 
and  proper  lubrication. 

General  directions*  —  Have  the  machine  examined  occasionally 
by  someone  well  posted  in  electric  motors  and  elevators.  The 
attendant  should  inspect  the  machine  often.  All  brushes  and 
switches  should  be  sufficiently  tight  to  give  a  good  contact,  but 
no  tighter.  None  of  the  brushes  should  spark  when  in  their 


768  HANDBOOK    ON    ENGINEERING. 

normal  position.  When  the  brushes  become  burnt  dress  witn 
sandpaper  or  file,  or,  if  necessary,  replace  with  new  ones.  If 
brushes  spark,  dress  with  sandpaper  or  file  to  a  good  bearing, 
and,  if  necessary,  set  up  springs,  but  do  not  make  the  ten- 
sion such  as  to  interfere  with  their  ready  movement.  Adjust 
commutator  brushes  gradually  for  least  sparking.  These  should 
be  close  to  the  central  position.  Contacts  and  brushes  should 
be  kept  clean  and  smooth  and  lubricated  sparingly.  While 
replacing  a  fusible  strip,  be  sure  that  main  switch  is  open,  and  be 
careful  not  to  touch  the  other  wire  with  your  tool  or  otherwise,  as 
such  contact  would  be  dangerous.  Never  put  in  a  larger  fuse 
than  the  one  burnt.  Inspect  the  worm  and  worm-wheel  occasion- 
ally through  hand-holes  in  casing,  to  see  that  they  are  well  lubri- 
cated, and  that  no  grit  gets  into  the  oil.  They  should  show  no 
wear.  The  stuffing-box  on  the  worm  shaft  should  be  only  tight 
enough  to  keep  the  oil  from  leaking  out  of  the  worm  chamber. 
Be  sure  that  all  parts  are  properly  lubricated,  and  that  none  of 
the  bearings  heat.  To  make  sure  that  the  car  and  machinery  run 
freely,  lift  brake  lever  and  then  rotate  worm  shaft  by  pulling  on 
the  brake  wheel.  The  empty  car  should  ascend  without  any  exer- 
tion. Keep  operating  cables  properly  adjusted.  Open  main 
switch  when  the  elevator  is  not  in  service. 

The  Lever. 

Relative  Position  of  Power,  Weight  and  Fulcrum  in  : 
Lever  of  the  first  class  Power.  Fulcrum.          Weight. 

Lever  of  the  second  class  Power.  Weight.  Fulcrum. 

Lever  of  the  third  class  Weight.  Power.  Fulcrum. 

Power  X  power-arm  Power  V  power-arm 

"—       =  Weight.  Weight  --  =  Weight-arm. 


Weight  X  weight-arm  Weight  X  weight-arm 

Power-arm       ~  -  Power'  Power  =  Powei"arm- 

Weight 
power  =  ratio  of,  or  proportion  of,  power-arm  to  weight-arm. 

Power-arm 

Weight-arm  =  ratio  of>  or  Pr°PortiO11  of  ;  weight  to  power. 


HANDBOOK    ON   ENGINEERING.  769 

CHAPTER     XXVI. 
ELECTRIC  ELEVATORS. 

Electric  elevators  of  the  drum  type  while  very  satisfactory  for 
buildings  of  moderate  height,  are  not  well  adapted  to  office  build- 
ings of  many  floors,  where  the  run  is  from  200  to  300  feet.  The 
objection  to  them  for  such  cases  is  that  the  drum  has  to  be  of  such 
large  dimensions  that  frequently  space  near  the  elevator  well  can- 
not be  had  for  it.  As  can  be  easily  seen  the  drum  must  be  of 
such  diameter  and  length  that  all  .the  rope  required  to  lift  the  car 
to  the  top  of  the  building  can  be  wound  upon  it.  If  the  diameter 
of  the  drum  is  enlarged  so  as  to  provide  the  requisite  surface, 
there  is  difficulty  in  obtaining  the  desired  car  speed,  because  the 
worm  gear  has  to  be  increased  proportionately  with  the  drum,  so 
that  the  pressure  in  the  teeth  may  be  not  so  great  as  to  cause  them  to 
cut.  If  the  worm  gear  is  large  the  motor  must  make  a  greater 
number  of  revolutions  for  each  turn  of  the  drum,  hence,  although 
the  car  will  travel  further  per  turn  of  drum,  the  increase  in  this 
direction  is  not  as  great  as  the  increase  in  the  ratio  between  the 
speed  of  the  motor  and  that  of  the  drum.  The  motor  speed  can 
be  reduced  considerably  by  using  a  worm  with  double  thread,  but 
even  then  high  motor  speed  is  required  for  high  car  speed,  higher 
than  with  elevators  running  to  a  moderate  height.  If  the  re- 
quired drum  surface  is  obtained  by  increasing  the  length  of  the 
drum,  then  the  machine  is  liable  to  become  so  wide  that  it  cannot 
be  placed  In  the  opening  at  the  side  of  the  elevator  well  provided 
for  it.  If  there  is  space  enough  for  the  machine,  the  spread  of 
the  ropes  when  they  are  unwinding  from  the  sides  of  the  drum 
may  be  greater  than  the  width  of  the  elevator  well. 


770  HANDBOOK    ON    ENGINEERING, 

It  was  to  overcome  the  above  difficulties  that  the  Sprague  screw 


Fig.  S37.    Diagram  of  Frazer  Duplex  Elevator* 

machine  was  devised,  bat  this  machine  has  not  withstood  the  test 


HANDBOOK    ON    ENGINEERING.  771 

of  time  and  is  no  longer  manufactured.  Another  machine  that 
overcomes  the  objections  to  the  drum  machine  for  high  buildings 
is  the  Frazer  Duplex  Motor  Elevator. 

The  general  arrangement  and  principle  of  operation  of  the 
Frazer  elevator  can  be  made  clear  by  the  aid  of  the  diagram  Fig. 
337.  As  will  be  seen  in  this  diagram  there  are  two  motors 
placed  one  on  top  of  the  other.  On  the  ends  of  the  amature 
shafts  are  mounted  grooved  sheaves,  and  under  these  sheaves  run 
endless  cables  in  the  manner  clearly  shown.  The  elevator  car  is 
suspended  from  the  frame  of  one  of  the  traveling  sheaves  around 
which  the  cables  pass,  and  a  counter-balance  weight  is  suspended 
from  the  frame  of  the  other  travelling  sheave.  The  two  motors 
are  arranged  to  rotate  in  opposite  directions,  as  indicated  by  the 
arrows.  In  the  operation  of  the  elevator  the  motors  never  re- 
verse, but  always  run  in  the  same  direction.  The  motors  are  of 
the  variable  speed  type,  and  the  running  of  the  elevator  car  in 
either  direction  is  effected  simply  by  changing  the  velocity  of  the 
motors.  Looking  at  the  diagram  it  can  be  seen  that  if  both 
motors  are  running  at  the  same  speed,  the  top  one  will  run  the 
cables  out  to  the  right  just  as  fast  as  the  lower  one  will  run  them 
to  the  left,  hence,  the  travelling  sheaves  will  not  move,  and  the 
car  will  stand  still.  Now  suppose  the  top  motor  runs  faster  than 
the  lower  one,  then  the  top  ropes  will  run  out  to  the  right  faster 
than  the  lower  ones  will  run  out  to  the  left,  and  as  a  result  the 
right  side  travelling  sheave  will  move  up,  and  the  other  one  will 
move  down,  thus  causing  the  car  to  rise,  and  the  counterbalance 
to  descend.  If  the  motor  velocities  are  reversed,  that  is,  the  top 
one  reduced  to  a  speed  lower  than  the  lower  one,  then  the  top 
one  will  not  run  the  cables  out  to  the  right  as  fast  as  the  lower 
one  will  run  them  to  the  left,  and  as  a  result  the  left  side  travel- 
ling sheave  will  rise,  thus  causing  the  car  to  run  down  and  the 
counterbalance  to  run  up.  By  varying  the  speed  of  the  two 


772 


HANDBOOK    ON  'ENGINEERING. 


motors  any  desired  velocity  of  the  car  can  be  obtained  from  zero 
to  the  maximum  running  in  either  direction. 


Fig.  3B7a.    Duplex  Motor. 

The  motors  used  are  made  so  that  their  speed  can  be  varied 
from  280  to  520  revolutions  per  minute,  the.  average  velocity 
being  400.  When  both  motors  are  running  at  400  the  car  stands 
still,  and  when  the  top  motor  runs  280  and  the  bottom  one  520 


HANDBOOK    ON    ENGINEERING.  773 

the  maximum  car  speed  is  obtained  with  the  car  on  the  up  trip. 
The  sheaves  on  the  shafts  of  the.  motor  armatures  are  about  19 
inches  in  diameter,  so  that  with  the  speeds  above  named,  the  car 
travels  about  600  feet  per  minute. 

Although  the  car  should  stand  still  when  the  two  motors  are 
running  at  the  same  speed,  in  practice  this  result  cannot  be 
obtained,  as  slight  variations  in  velocity  will  occur,  and  these 
fluctuations  will  cause  the  car  to  shake.  To  overcome  this 
trouble  a  brake  is  provided  to  hold  the  top  sheave  over  which  the 
car  lifting  ropes  pass,  as  clearly  shown  in  the  diagram.  Gener- 
ally the  motors  are  stopped  when  the  elevator  is  stopped. 

This  elevator  is  the  most  perfect  in  operation  of  any  electric 
elevator  that  has  been  devised,  its  velocity  can  be  varied  at  the 
will  of  the  car  operator  from  zero  to  the  maximum  speed,  and  it 
can  be  stopped  and  reversed  when  running  at  full  speed  without 
producing  the  slightest  jolt ;  but  it  possesses  undesirable  features 
that  tend  to  offset  its  fine  running  qualities.  The  main  objection 
is  that  the  driving  sheaves  mounted  on  the  ends  of  the  armature 
shaft  have  to  be  of  very  small  diameter,  so  as  to  not  impart  too 
high  a  velocity  to  the  driving  ropes.  As  these  sheaves  are  only 
19  inches  in  diameter,  steel  ropes  cannot  be  used,  in  their  stead 
hemp  ropes  with  a  steel  core  are  used,  and  while  these  may  be 
just  as  safe  as  steel  cables,  they  do  not  inspire  the  same  amount 
of  confidence. 

•  As  there  is  very  little  friction  about  the  Frazer  elevator,  it 
would  naturally  be  inferred  that  it  will  require  less  current  to  do 
the  same  work,  but  actual  practice  seems  to  show  that  it  ia  not 
any  more  economical  than  the  drum  machine. 

The  duplex  motor  of  the  Frazer  elevator  is  shown  in  Fig.  337a, 
and  is  so  simple  as  to  require  no  explanation,  being  in  fact  noth- 
ing but  two  motors  mounted  one  on  top  of  the  other. 

The  way  in  which  the  Frazer  elevator  is  controlled  can  be  ex- 
plained in  connection  with  the  wiring  diagram  Fig.  338.  The 


774 


HANDBOOK    ON    ENGINEERING. 


s 

I 

s 


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2 


bo 


upper  part  of   the  diagram  represents   the  car  switch,  a   photo- 
graphic view  of  which  is  shown  in  Fig.  338a.     The  car  switch  is 


HANDBOOK    ON    ENGINEERING. 


775 


Fig.  338a.    Frazer  Car  Controller. 

provided  with  resistances  that  can  be  connected  in  parallel  with 
the  field  coils  of  either  motor,  so  as  to  vary  the  velocity.  The 
parts  marked  U  limit,  and  D  limit  are  automatic  stopping  switches 
that  are  located  in  the  elevator  well  near  the  top  and  bottom,  and 
in  such  position  that  they  may  be  moved  by  the  elevator  car  when 
it  reaches  either  end  of  its  travel.  These  limit  switches  stop  the 
car  gradually  by  cutting  in  the  resistance  in  the  manner  clearly 
indicated  in  the  diagram.  A  photographic  view  of  the  D  limit 
switch  is  given  in  Fig  338b.  The  U  limit  switch  is  substantially 
the  same  in  construction  and  appearance.  As  will  be  seen  the 
switch  lever  is  actuated  by  a  rod  that  carries  a  roller  at  its  end, 
this  roller  being  placed  in  a  position  where  it  will  be  struck  by  an 
inclined  plane  attached  to  the  elevator  car,  so  as  to  gradually 


776  HANDBOOK    ON    ENGINEERING. 

cut  the  resistance  into  the  circuit.  The  lower  part  of  the  dia- 
gram constitutes  the  controller  and  the  several  switches  of  which 
it  is  composed  are  assembled  on  a  slate  panel  in  the  manner 
shown  in  Fig.  338o,  which  is  a  photographic  view  of  the  con- 
troller front. 

The  operation  of  the  controller  is  as  follows :  —  The  potential 
switch  is  jlosed  by  hand,  but  is  arranged  like  a  circuit  breaker, 
so  that  it  will  open  whenever  the  potential  of  the  current  dies  out. 
To  start  the  motors,  the  car  switch  D  is  closed,  and  then  a  cur- 


Fig.  338b.    Frazer  Limit  Switch. 

rent  starting  from  A  will  pass  through  D  and  thence  through  the 
magnet  of  S  and  following  the  path  indicated  by  the  arrow  heads 
will  reach  wire  E  and  thus  return  to  the  lower  side  of  the  potent- 
ial switch.  As  soon  as  the  magnet  of  S  is  energized,  the  contact 
plates  will  be  raised  so  as  to  close  the  main  circuit,  and  then  the 
current  will  flow  through  the  starting  series  field  and  thence 
through  the  armatures  of  the  two  motors  and  back  to  lower  side 
of  potential  switch.  From  the  end  of  the  series  field  a  current 
will  branch  off  through  the  magnet  of  AS'  and  through  the  magnets 


HANDBOOK    ON    ENGINEERING. 


777 


of  the  switches  that  cut  out  the  series  field.  The  shunt  fields  of 
the  two  motors  are  connected  in  series  and  to  the  left  side  contact 
at  top  of  switch  S'  and  to  the  lower  right  side  contact  of  $.  To 


Fig.  338c.     Front  of  Frazer  Controller. 

make  the  car  run  in  either  direction  it  is  necessary  to  change  the 
speed  of  the  motors,  and  this  is  done  by  moving  the  contact  B  in 
the  car  switch,  by  means  of  the  operating  lever,  to  one  side  or  the 


778  HANDBOOK    ON    ENGINEERING. 

other.  Let  B  be  moved  to  the  left,  then  current  coming  up  from 
A  will  pass  through  B  to  the  lever  of  the  U  limit  and  thence  fol- 
low the  arrow  heads  to  point  C  between  the  shunt  field  coils  of 
the  two  motors.  In  this  way  the  resistance  in  the  car  switch  is 
connected  in  parallel  with  the  field  coil  on  the  right  of  (7,  hence, 
the  field  of  this  motor,  will  receive  less  current  than,  the  field  of 
the  other  motor,  and  as  a  result  its  amature  will  run  faster. 
If  B  is  moved  to  the  right,  then  current  will  flow  from  point  C  in 
the  opposite  direction,  as  indicated  by  the  arrows  a,  and  reaching 
the  D  limit  will  pass  through  the  lever  and  thence  through  the  car 
switch  resistance,  through  B  and  thence  through  wire  E  will 
reach  points  F.  In  this  case  all  the  field  current  will  pass 
through  the  right  side  field  but  at  C  it  will  divide  part  going 
through  the  left  side  field  and  the  remainder  following  the  path  of 
arrows  a  to  point  F.  Thus  by  swinging  the  lever  of  the  car 
switch  to  one  side  or  the  other,  one  or  the  other  of  the  motors  can 
be  made  to  run  faster  and  the  direction  of  the  car  can  be  reversed, 
while  the  speed  can  be  varied  as  may  be  desired. 

THE  TRACTION  TYPE  OF  ELECTRIC  ELEVATOR. 

Another  form  of  electric  elevator  designed  to  overcome  the 
disadvantages  of  drum  machines  for  high  runs  is  what  is  known  as 
the  traction  type,  and  is  illustrated  diagrammatically  in  Fig.  339 
on  the  left  side.  In  this  construction  only  one  motor  is  used  and 
on  the  end  of  its  armature  shaft  is  mounted  a  sheave  much  larger 
than  those  used  on  the  Frazer  machine.  The  size  of  the  sheave 
is  large  enough  to  permit  the  use  of  regular  steel  wire  cables. 
These  cables  pass  over  two  travelling  sheaves,  in  the  manner 
clearly  shown  in  the  diagram,  and  the  ends  are  anchored  to  suit- 
able supports  as  shown.  The  car  is  suspended  from  ropes  that 
pass  over  a  sheave  at  tlie  top  of  the  elevator  well  and  run  down  to 
the  frame  of  one  of  the  travelling  sheaves.  The  counterbalance 
is  similarly  connected  with  the  other  sheave  frame. 


HANDBOOK    ON    ENGINEERING.  779 

From  an  inspection  of  the  diagram  it  will  be  seen  that  this  ma- 


MODIFIED  FORM' 


Fig.  389.    Traction  Types  of  Electric  Elevator. 

chine  is  geared  two  to  one,  that  is,  the  car  speed  is  one-half  the 


780  HANDBOOK      ON    ENGINEERING. 

velocity  of  the  circumference  of  the  driving  sheave  on  the  motor 
shaft.  In  the  Frazer  machine  the  car  is  ran  in  either  direction 
while  the  motors  always  run  in  the  same  direction,  and  the  car 
can  be  stopped  without  stopping  the  motors,  simply  by  bringing 
the  two  to  the  same  speed.  In  the  traction  system  this  cannot 
be  done,  the  motor  must  be  stopped  to  stop  the  car,  and  it  must 
be  reversed  to  reverse  the  direction  of  the  car.  For  these  reasons 
the  control  is  not  so  perfect  as  in  the  Frazer  machine,  but  the 
difference  is  slight  in  practice,  in  fact  hardly  worth  noticing ;  but 
as  an  offset  we  have  the  fact  that  a  sheave  of  standard  size  can  be 
placed  on  the  motor  shaft  and,  therefore,  regular  steel  ropes  can 
be  used  instead  of  hemp  ropes  with  a  steel  centre. 

In  looking  at  the  diagram  this  arrangement  of  elevator  appears 
to  be  as  simple  as  anything  can  be,  but  the  actual  apparatus  is 
not  as  simple  as  the  diagram.  The  traveling  sheaves  have  to  run 
in  guides  and  these  must  extend  something  more  than  half  the 
height  of  the  elevator  well.  Such  guides  are  expensive,  and  in 
addition  take  up  a  considerable  amount  of  space,  which  in  office 
buildings  in  large  cities  is  very  valuable.  Now  it  can  be  easily 
seen  that  if  a  motor  can  be  made  that  will  drive  an  elevator  by 
being  geared  two  to  one  as  in  the  diagram,  it  is  only  necessary  to 
make  the  motor  so  as  to  pull  twice  as  hard  and  then  it  can  be 
connected  directly  with  the  elevator.  To  do  this  the  size  of  the 
motor  must  be  increased,  but  as  an  offset  we  have  the  fact  that 
all  the  expense  of  the  traveling  sheaves  can  be  used  to  cover  the 
additional  cost  of  the  motor,  and  the  space  occupied  by  the  sheave 
is  saved,  which  is  so  much  clear  gain,  in  addition  to  which  the 
greater  simplicity  must  be  taken  account  of.  An  elevator  of  this 
type  is  shown  in  the  diagram  at  the  right  of  Fig.  339,  and  it  is 
known  as  one  to  one  cable  drive  elevator. 

This  elevator  which  has  been  developed  by  the  Otis  Elevator 
Company  is  now  being  introduced  for  high  speed  elevators  in 
large  office  and  other  buildings.  The  principle  of  operation  is 


HANDBOOK    ON    ENGINEERING. 


781 


the  same  as  that  used  in  cable  railroads.  The  motor  carries  on 
the  end  of  the  amature  shaft  a  grooved  sheave  about  36  inches  in 
diameter,  and  an  idle  sheave  is  placed  directly  above  the  motor 
sheave.  The  lifting  ropes  pass  over  the  upper  sheave  once, 
and  under  the  motor  sheave  twice.  This  double  wrap  around  the 
the  driving  sheave  has  been  found  by  many  trials  to  give  all  the 


Fig.  340.    Cable  Drive  Elevator  Machine. 

adhesion  required  to  lift  the  heaviest  loads  the  elevator  can  carry. 
A  side  view  of  the  motor  is  shown  in  the  centre  of  diagram  Fig. 
339,  from  which  the  relative  position  of  the  driving  and  the  idle 


782  HANDBOOK    ON    ENGINEERING. 

sheave  can  be  understood.  The  construction  is  still  better  shown 
in  Fig.  340  which  is  a  photographic  view  of  the  motor.  The 
brake  on  the  motor  is  located  between  the  field  frame  and  the 
bearing  at  the  driving  sheave  end,  and  is  actuated  by  powerful 
springs.  A  magnet  is  used  to  pull  the  brake  off  when  the  motor 
is  running.  As  soon  as  the  current  stops  the  magnet  releases  the 
brake  and  the  springs  apply  it  with  all  the  force  necessary  to  pre- 
vent the  shaft  from  rotating  even  with  ithe  heaviest  load  in  the 
car.  The  counterbalance  weight  used  with  these  elevators  weighs 
as  much  as  the  car  and  one-half  the  maximum  load  that  it  is  in- 
tended to  lift,  from  which  it  will  be  seen  that  the  break  does  not 
have  to  be  so  powerful  as  might  appear  at  a  first  glance. 

In  some  cases  these  elevator  machines  are  placed  at  the  top  of 
the  elevator  well,  and  then  the  idle  sheave  is  placed  under  the 
motor,  and  is  secured  to  overhead  framing  provided  for  the 
the  purpose.  Such  a  construction  is  shown  in  Fig.  340a  which  is 
a  perspective  view  of  a  complete  elevator,  broken  away  at  two 
places  so  as  to  shorten  the  picture. 

The  elevator  machine  has  no  safety  appliances  attached  to  it 
other  than  the  break,  as  none  are  required  upon  it.  The  auto- 
matic stops  are  arranged^in  the  elevator  well  mear  the  top  and  bot- 
tom landings,  in  a  manner  that  will  be  explained  presently.  The 
break  on  the  motor  is  arranged  so  that  normally  it  acts  with  a 
moderate  pressure,  but  if  the  occasion  requires  it  the  breaking 
force  can  be  instantly  increased  by  simply  moving  the  operating 
switch  in  the  car  to  the  central  position.  The  connections  of  the 
motor  with  the  controller  are  such  that  in  stopping  the  motor  is 
converted  into  a  generator,  and  thus  has  to  be  driven  by  the  force 
of  the  descending  weight. 

As  will  be  seen  in  Fig.  340a  there  is  a  small  governor  located 
by  the  side  of  the  moter,  this  is  the  regular  Otis  safety  governor 
that  is  arranged  so  as  to  stop  the  car  if  it  attains  an  excessive 
velocity  from  any  cause.  In  this  machine  this  governor  has  an 


HANDBOOK    ON    ENGINEERING. 


783 


Fig.  340a. 

additional  appliance  consisting  of  a   switch  that  acts  to  stop  the 


784 


HANDBOOK   ON   ENGINEERING. 


motor  whenever  the  governor  throws  the  car  safeties  into  action, 
thus  preventing  the  lifting  ropes  from  becoming  slack. 


HANDBOOK    ON    ENGINEERING. 


785 


This  cable  drive  elevator  is  arranged  so  as  to  run  at  different 
speeds,  the  result  being  accomplished  by  the  movement  of  the  arc 
switch  handle  to  different  positions.  The  change  in  the  velocity 
of  the  motor  is  effected  in  different  ways.  In  one  arrangement 


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5 


of  the  controlling  devices,  the  speed  variation  is  obtained  by  vary- 
ing the  strength  of  the  current  passing  through  the  field  of  the 
motor;  in  another  it  is  obtained  by  introducing  resistance  in  the 
armature  circuit,  and  by  sending  more  or  less  current  through  a 


78(5  HANDBOOK    ON    ENGINEERING. 

by  pass  around  the  armature.  In  another  arrangement  both  these 
methods  are  combined.  The  wiring  diagram,  Fig.  341,  illus- 
trates the  latter  arrangement.  The  appearance  of  the  controller 
to  which  this  diagram  corresponds  is  shown  in  Fig.  34 la. 

In  the  wiring  diagram,  Fig.  341,  the  heavy  lines  indicate  wires 
through  which  the  strong  armature  current  passes,  the  fine  lines 
are  wires  through  which  the  field  current,  and  the  switch  magnet 
currents  pass.  A  complete  explanation  of  this  diagram  would  be 
very  lengthy,  and  to  avoid  this  we  have  placed  arrow  heads  on  all 
the  lines  which  will  greatly  facilitate  the  understanding  of  the 
condensed  explanation  that  follows :  — 

The  line  wires  are  connected  with  the  two  pole  switch  at  the 
right  of  the  diagram.  From  this  switch  connections  run  to  a 
potential  switch  directly  to  the  left.  The  accelerating  magnet 
cuts  out  the  resistance  shown  above  it,  from  the  armature  circuit, 
when  the  highest  velocity  is  desired.  Directly  to  the  left  of  the 
accelerating  magnet  are  shown  a  number  of  magnetic  switches, 
that  act  to  cut  resistance  out  of  the  armature  circuit,  and  to  in- 
crease the  resistance  in  a  circuit  that  shunts  the  armature,  and 
finally  to  open  this  circuit.  These  switches  are  operated  from 
the  car  switch,  which  is  shown  at  the  left  side  of  the  diagram. 
The  circle  marked  A  represents  the  motor  armature,  and  at  the 
bottom  of  the  diagram  is  shown  the  shunt  field  coils.  The  motor 
is  of  the  plain  shunt  type.  Following  the  wire  starting  from  A  it 
will  be  seen  that  it  passes  through  the  field  coils  of  the  motor  and 
ends  at  B.  The  circuit  from  A  through  the  potential  switch  can 
be  easily  traced  to  (7,  and  from  here  the  fine  wire  runs  through 
switch  5,  to  and  through  E,  and  from  here  to  switch  1  and  to  the 
lower  up  contact  of  the  car  switch.  E  is  the  magnet  coil  of  one 
of  the  starting  switches  E' ',  and  if  the  car  switch  is  turned  so  as 
to  cover  the  first  contact,  the  current  after  reaching  this,  will  re- 
turn through  the  centre  wire  from  the  car  and  reach  the  point  0' 
on  the  potential  switch.  The  current  will  then  flow  through  the 


HANDBOOK    ON    ENGINEERING.  787 

motor  by  way  of  switch  E'  in  the  way  indicated  by  the  arrow 
heads.  As  the  car  switch  is  advanced  it  covers  in  succession  the 
contacts  from  which  lead  wires  that  pass  through  the  roller 
switches,  1,  2,  2,  3,  5,  and  thence  to  the  magnets  of  the  switches 
that  cut  the  resistances  A'  into  the  circuit  that  shunts  the  arma- 
ture, and  cut  out  the  resistances  directly  above,  that  are  in  series 
with  the  armature.  In  this  way  the  motor  speed  is  increased. 
When  the  accelerating  magnet  cuts  out  all  its  resistance  it  also 
closes  the  circuit  of  F  and  then  resistance  F'  is  cut  into  the 
shunt  field  circuit,  and  the  motor  speed  further  increased.  The 
roller  switches  1,  2,  3,  4,  5,  are  limit  switches  to  stop  the  car 
automatically  at  the  top  floor,  if  the  operator  fails  to  turn  the  car 
switch  to  the  stop  position.  Similar  limit  switches  are  shown  in 
the  wires  running  from  the  do.wn  side  of  the  car  switch.  In  Fig. 
340a  two  of  these  switches  can  be  seen  at  the  side  of  the  guide 
near  the  bottom  of  the  well.  The  two  roller  switches  seen  at  the 
right  of  the  diagram  are  final  limit  switches  that  are  actuated  if 
the  car  overruns  the  limits.  When  one  of  these  switches  is 
moved,  the  motor  is  disconnected  from  the  circuit,  the  brake 
goes  on  with  full  force,  the  armature  generates  a  strong  current 
and  the  motor  stops  at  once. 


788  HANDBOOK    ON    ENGINEERING. 


CHAPTER    XXVII. 

THE  DRIVING  POWER  OF  BELTS. 

The  average  strain  or  tension  at  which  belting  should  be  run 
is  claimed  to  be  55  pounds  for  every  inch  in  width  of  a  single  belt, 
and  the  estimated  grip  is  one-half  pound  for  every  square  inch  of 
contact  with  pulley,  when  touching  one-half  of  the  circumference 
of  the  pulley.  For  instance  a  belt  running  around  a  36-inch  pul- 
ley would  come  in  contact  with  one-half  its  circumference,  or  56£ 
inches,  and  allowing  a  half-pound  per  inch,  would  have  a  grip  28£ 
pounds  for  each  inch  of  width  of  belt. 

MECHANICAL  PROBLEMS  AND  RULES. 

Problem  1.  To  find  the  circumference  of  a  circle  or  a 
pulley :  — 

Solution.  Multiply  the  diameter  by  3.1416  ;  or,  as  7  is  to  22 
so  is  the  diameter  to  the  circumference. 

Problem  2.     To  compute  the  diameter  of  a  circle  or  pulley :  — 

Solution.  Divide  the  circumference  by  3.1416;  or  multiply 
the  circumference  by  .3183  ;  or  as  22  is  to  7,  so  is  the  circumfer- 
ence to  the  diameter,  equally  applicable  to  a  train  of  pulleys,  the 
given  elements  being  the  diameter  and  the  circumference. 

Problem  3.  To  find  the  number  of  revolutions  of  driven  pulley, 
the  revolution  of.driver,  and  diameter  of  driver  and  driven  being 
given :  — 

Solution.  Multiply  the  revolutions  of  driver  by  its  diameter, 
and  divide  the  product  by  the  diameter  of  driven. 


HANDBOOK    ON  ENGINEERING.  789 

Problem  4.  To  compute  the  diameter  of  driven  pulley  for  any 
desired  number  of  revolutions,  the  size  and  velocity  of  driver 
being  known :  — 

Solution.  Multiply  the  velocity  of  driver  by  its  diameter  and 
divide  the  product  by  the  number  of  revolutions  it  is  desired  the 
driven  shall  make. 

Problem  5.     To  ascertain  diameter  of  driving  pulley :  — 

Solution.  Multiply  the  diameter  of  driven  by  the  number  of 
revolutions  it  is  desired  it  shall  make,  and  divide  the  product  by 
the  number  of  revolutions  of  the  driver. 

6.  Rule  for  finding;  length  of  belt  wanted:  Add  the  diame- 
ters of  the  two  pulleys  together,  divide  the  result  by  two,  and 
multiply  the  quotient  by  3  1/7.  Add  the  product  to  twice  the 
distance  between  the  centers  of  the  shafts,  and  we  have  the 
length  required. 

FOR  CALCULATING  THE  NUMBER  OF  HORSE-POWER  WHICH  A  BELT 
WILL  TRANSMIT,  ITS  VELOCITY  AND  THE  NUMBER  OF  SQUARE  INCHES 
IN  CONTACT  WITH  THE  PULLEY  BEING  KNOWN. 

Divide  the  number  of  square  inches  of  belt  in  contact  with  the 
pulley  by  two,  multiply  this  quotient  by  velocity  of  the  belt  in 
feet  per  minute  and  divide  the  product  by  33,000  ;  the  quotient  is 
the  number  of  horse-power. 

Example.  —  A  20-inch  belt  is  being  moved  with  a  velocity  of 
2,000  feet  per  minute,  with  six  feet  of  its  length  in  contact 
with  the  circumference  of  a  four-foot  drum ;  desired  its  horse- 
power. 20  x  72  equal  1,440,  divided  by  two,  equals  720,  x  2,000 
equal  1,440,000,  divided  by  33,000  equals  43|  horse-power. 

Rule  for  finding  width  of  belt,  when  speed  of  belt  in  feet  per 
minute  and  horse-power  wanted  are  given :  — 

For  single  belts*  —  Divide  the  speed  of  belt  by  800.  The  horse- 
power wanted  divided  by  this  quotient,  will  give  the  width  of 
belt  required. 


790  HANDBOOK    ON    ENGINEERING. 

Example.  — Required  the  width  of  single  belt  to  transmit  100 
horse-power.     Engine  pulley  72"  in  diameter.     Speed  of  engine, 
.  220  revolutions  per  minute. 

800)  4146  (speed  of  belt  per  minute). 

5.18)100.00  (horse-power  wanted). 
19"  width  of  belt  required. 

For  doable  belts*  —  Divide  the  speed  of  belt  in  feet  per  minute 
by  560.  Divide  the  horse-power  wanted  by  this  quotient  for  the 
width  of  belt  required. 

Example.  —  Required  the  width  of  double  belt  to  transmit  500 
horse-power.  Engine  pulley  72"  in  diameter.  Speed  of  engine, 
220  revolutions  per  minute. 

560)4146  (speed  of  belt  per  minute). 
7.4)500.00  (horse-power  wanted). 
67J"  width  of  belt  required. 

NOTES  ON  BELTS. 

PRINCIPLES    GOVERNING    BELTS. 

Although  there  is  not  near  as  much  known  in  general  about 
the  power  of  transmitting  agencies  as  there  should  be,  still  it 
seems  that  almost  any  other  method  or  means  is  better  understood 
than  belts. 

One  of  the  chief  difficulties  in  the  way  of  a  better  knowledge  of 
the  belting  problem,  is  the  relation  that  belts  and  pulleys  bear  to 
each  other.  The  general  supposition,  and  one  that  leads  to  many 
errors,  is  that  the  larger  in  diameter  a  pulley  is,  the  greater  its 
holding  capacity  —  the  belt  will  not  slip  "so  easily,  is  the  belief. 
But  it  is  merely  a  belief,  and  has  nothing  to  sustain  it,  unless  it 
be  faith,  and  faith  without  work  is  an  uncertain  factor.  It  is  very 


HANDBOOK    ON    ENGINEERING.  791 

desirable  to  impress  upon  the  minds  of  all  interested,  the  folio  wing 
immutable  principles  or  law :  — 

1.  The  adhesion  of  the  belt  to  the  pulley  is  the  same  —  the  arc 
or   number   of  degrees   of  contact,  aggregate  tension  or  weight 
being  the  same  —  without  reference  to  width  of  belt  or  diameter 
of  pulley. 

2.  A  belt  will  slip  just  as  readily  on  a  pulley  four  feet  in  diam- 
eter, as  it  will  on  a  pulley   two  feet  in   diameter,    provided  the 
conditions  of  the  faces  of  the  pulleys,  the  arc  of  contact,  the  ten- 
sion, and  the  number  of  feet  the  belt  travels  per  minute  are  the 
same  in  both  cases. 

3.  A  belt  of  a  given  width  and  making  two  thousand,  or  any 
other  given  number  of  feet  per  minute,  will  transmit  as  much 
power   running   on   pulleys   two   feet   in  diameter   as  it  will  on 
pulleys  four  feet  in  diameter,  provided  the  arc  of  contact,  tension 
and  conditions  of  pulley  faces  all  be  the  same  in  both  cases. 

It  must  be  remembered,  in  reference  to  the  first  rule,  that  when 
speaking  of  tensions,  that  aggregate  tension  is  never  meant  unless 
so  specified.  A  belt  six  inches  wide,  with  the  same  tension,  or 
as  taut  as  a  belt  one  inch  wide,  would  have  six  times  the  aggre- 
gate tension  of  the  one  inch  belt.  Or  it  would  take  six  times 
the  force  to  slip  the  six  inch  belt  as  it  would  the  one  inch.  It 
is  well  to  induce  readers  to  become  practical  students  and  to  be 
able  to  learn  for  themselves.  Information  obtained  in  that  way 
is  far  more  valuable,  and  liable  to  last  much  longer. 

In  order  that  the  reader  may  more  fully  understand  whether 
or  not  a  large  pulley  will  hold  better  than  a  small  one,  let  him 
provide  a  short,  stout  shaft,  say  three  or  four  feet  long  and  two 
inches  in  diameter.  To  this  shaft  firmly  fasten  a  pulley,  say 
12  in.  in  diameter,  or  any  other  size  small  pulley  that  may  be 
convenient.  The  shaft  must  then  be  raised  a  few  feet  from  the 
floor  and  firmly  fastened,  either  in  vises,  or  by  some  other  means, 
so  that  it  will  not  turn.  It  would  be  better,  of  course,  to  have 


792  HANDBOOK    ON    ENGINEERING. 

a  smooth-faced  iron  pulley,  as  such  are  most  generally  used.  So 
far  as  the  experiment  is  concerned,  it  would  make  no  difference 
what  kind  of  a  pulley  was  used,  provided  all  the  pulleys  experi- 
mented with  be  of  the  same  kind,  and  have  the  same  kind  of  face 
finish.  When  the  shaft  and  pulleys  are  fixed  in  place,  procure  a 
new  leather  belt  and  throw  it  over  the  pulley.  To  one  end  of  the 
belt  attach  a  weight,  equal,  say,  to  forty  pounds  —  or  heavier,  if 
desired  —  for  each  inch  in  width  of  belt  used ;  let  the  weight 
rest  on  the  floor.  To  the  other  end  of  the  belt  attach  another 
weight,  and  keep  adding  to  it  until  the  belt  slips  and  raises  the 
first  weight  from  the  floor.  After  the  experimenter  is  satisfied 
with  playing  with  the  12  in.  pulley,  he  can  take  it  off  the 
shaft  and  put  on  a  24  in.,  a  36  in.,  or  any  other  size  he  may 
wish ;  or,  what  is  better,  he  can  have  all  on  the  shaft  at  the 
same  time.  The  belt  can  then  be  thrown  over  the  large  pulley 
and  the  experiment  repeated.  It  will  then  be  found  if  pulley 
faces  are  alike,  that  the  weight  which  slipped  the  belt  on  the 
small  pulley  will  also  slip  it  on  the  large  one.  The  method 
shows  the  adhesion  of  a  belt  with  180  degrees  contact,  but  as  the 
contact  varies  greatly  in  practice,  it  is  well  enough  to  understand 
what  may  be  accomplished  with  other  arcs  of  contact.  But,  after 
all,  many  are  probably  at  a  loss  how  to  account  for  some  obser- 
vations previously  made.  They  have  noticed  that  when  a  belt  at 
actual  work  slipped,  an  increase  in  the  size  (diameter)  of  the 
pulleys  remedied  the  difficulty  and  prevented  the  slipping. 

A  belt  has  been  known  to  refuse  to  do  the  work  allotted  to  it, 
and  continue  to  slip  over  pulleys  two  feet  in  diameter,  but  from 
the  moment  pulleys  were  changed  to  three  feet  in  diameter  there 
was  no  further  trouble.  These  observed  facts  seem  to  be  at 
variance  with  and  to  contradict  the  results  of  the  experiments 
that  have  been  made.  All,  however,  may  rest  assured  that  it  is 
only  apparent,  not  real. 

The  resistance  to  slippage  is  simply  a  unit  of  useful  effect  (or 


HANDBOOK    ON    ENGINEERING.  793 

that  which  can  be  converted  into  useful  effect).  The  magnitude 
of  the  unit  is  in  proportion  to  the  tension  of  the  belt.  The  sum 
total  of  useful  effect  depends  upon  the  number  of  times  the  unit 
is  multiplied.  A  belt  6  inches  wide  and  having  a  tension  equal 
to  40  Ibs.  per  inch  in  width,  and  traveling  at  the  rate  of  1  foot 
per  minute,  will  raise  a  weight  of  240  Ibs.  1  foot  high  per  minute. 
If  the  speed  of  the  belt  be  increased  to  136.5  feet  per  minute,  it 
will  raise  a  weight  of  33,000  Ibs.  per  minute,  or  be  transmitting 
1  horse-power.  The  unit  of  power  transmitted  by  a  belt  is  rather 
more  than  its  tension,  but  to  take  it  at  its  measured  tension  is  at 
all  times  safe,  and  40  to  45  Ibs.  of  a  continuous  working  strain  is 
as  much,  perhaps,  as  a  single  belt  should  be  subjected  to.  A 
little  reflection  will  now  convince  the  reader  that  a  belt  transmits 
power  in  proportion  to  its  lineal  speed,  without  reference  to  the 
diameter  of  the  pulleys.  Having  arrived  at  that  conclusion,  it  is 
then  easy  to  understand  why  it  is  that  a  belt  working  over  36-inch 
pulley  will  do  its  work  easy,  when  it  refused  to  do  it  and  slipped 
on  24-inch  pulleys.  If  the  belt  traveled  800  feet  per  minute  on 
the  24-inch  pulleys,  on  the  36-inch  it  would  travel  1,200  feet, 
thus  giving  it  one-half  more  transmitting  power.  If,  in  the  first 
instance,  it  was  able  to  transmit  but  8  horse-power,  in  the  second 
instance  it  will  transmit  12  horse-power.  All  of  which  is  due  to 
the  increase  in  the  speed  of  the  belt  and  not  to  the  increase  in  the 
size  of  the  pulleys ;  because,  as  has  been  shown,  the  co-efficient 
of  friction,  or  resistance  to  slippage,  is  the  same  on  all  pulleys 
with  the  same  arc  of  belt  contact. 

There  is  no  occasion  for  elaborate  and  perplexing  formulas  and 
intricate  rules.  They  serve  no  useful  purpose,  but  tend  only  to 
mystify  and  puzzle  the  brain  of  all  who  are  not  familiar  with  the 
higher  branches  of  mathematics,  —  and  it  is  the  fewest  number 
of  our  every-day  practical  mechanics  who  are  so  familiar.  In  all, 
or  nearly  all  treatises  on  belting,  the  statement  is  made  that  at 
600,  800  or  1,000  feet  per  minute,  as  the  case  may  be,  a  belt  one 


794  HANDBOOK    ON    ENGINEERING. 

inch  wide,  will  transmit  one  horse-power ;  and  yet,  when  we  come 
to  apply  these  rules  in  practice,  no  such  results  can  be  obtained 
one  time  in  ten.  The  rules  are  just  as  liable  to  make  the  belt 
travel  400,  1,000  or  1,600  per  minute  per  horse-power  as  the 
number  of  feet  they  may  give  as  indicating  a  horse-power. 

All  .of  the  following  simple  calculations  are  based  upon  the 
assumption  that  a  belt  traveling  800  feet  per  minute,  and  running 
over  pulleys,  both  of  which  are  the  same  diameters,  will  easily 
transmit  one  horse-power  for  each  inch  in  width  of  belt.  A  belt 
under  such  circumstances  would  have  180  degrees  of  contact  on 
both  pulleys  without  the  interposition  of  idlers  or  tighteners. 

The  last  proposition  being  accepted  as  true  and  the  basis  cor- 
rect, the  whole  matter  resolves  itself  into  a  very  simple  problem, 
so  far  as  a  belt  with  180  degrees  contact  is  concerned.  It  is 
simply  this :  If  a  belt  traveling  800  feet  per  minute  transmit  one 
horse-power,  at  1,600  feet,  it  will  transmit  two  horse-power ;  or 
if  2,400  feet,  three  horse-power,  and  so  on.  It  is  no  trouble  for 
any  one  to  understand  that,  if  he  understands  simple  multiplica- 
tion or  division. 

It  is  not,  however,  always  the  case  that  both  pulleys  are  the 
same  size,  and  as  soon  as  the  relative  sizes  of  the  pulleys  change, 
the  transmitting  power  of  the  belt  changes ;  and  that  is  the  rea- 
son why  no  general  rule  has  ever,  or  ever  will  be  made  for  ascer- 
taining the  transmitting  capacity  of  belts  under  all  circumstances. 
When  the  pulleys  differ  in  size,  the  larger  of  the  two  is  lost  sight 
of  —  it  no  longer  figures  in  the  calculations  —  the  small  pulley, 
only,  must  be  considered.  To  get  at  it,  the  number  of  degrees 
of  belt  contact  on  the  small  pulley  must  be  ascertained  as  nearly 
as  possible  and  use  for  a  guide,  for  getting  at  the  transmitting 
power,  the  next  established  basis  given.  Of  course,  the  experi- 
menter can  make  a  rule  for  every  degree  of  variation,  but  it  would 
require  a  great  many,  and  is  not  necessary.  Five  divisions  are 
used,  as  follows:  — 


HANDBOOK   ON   ENGINEERING.  795 

For  180    degrees  useful   effect  ....     100 

For  157|       "  "           "  92 

For  135         "  "        '  "  84 

For  112i       u  44          fi  76 

For     90         "  "          "  64 

The  experimenters  may  find  that  the  figures  are  under  obtained 
results,  which  is  exactly  what  they  are  intended  to  be,  more 
especially  on  the  90  degree  basis.  Always  make  ample  allow- 
ance. 

To  ascertain  the  power  a  belt  will  transmit  under  the  first-named 
conditions :  Divide  the  speed  of  the  belt  in  feet  per  minute  by 
800,  multiply  by  its  width  in  inches  and  by  100.  For  the  second, 
divide  by  800,  multiply  by  width  in  inches  and  by  .92.  Third 
place,  divide  by  800,  multiply  by  width  in  inches  and  by  .84. 
Fourth  place,  divide  by  800,  multiply  by  width  in  inches  and  by 
.76.  Fifth  place,  divide  by  800,  multiply  by  width  in  inches  and 
by  .64.  As  an  example:  What  would  be  the  transmitting  power 
of  a  16-inch  belt  traveling  2,500  feet  per  minute  by  each  of  the 
above  rules? 

1st:  2,500  divided  by  800  equal  3.125  x  16  x  100  equal  50  h.  p. 
2d:    2,500         "  800      "     3.125  x  16  x  .92  equal  46    " 

3d:    2,500         "  800      "     3.125  x  16  x  .84  equal  42    " 

4th:  2,500         "  800      "     3.125  x  16  x  .76  equal  38    " 

5th:  2,500         "  800      "     3.125  x  16  x  .64  equal  32    " 

As  stated,  when  the  degrees  of  contact  come  between  the 
divisions  named  above,  in  order  to  be  on  the  safe  side,  calculate 
from  the  first  rule  below  it,  or  make  it  approximate  as  desired. 

If  the  above  rule  is  studied  well  and  strictly  used,  there  can 
be  no  excuse  for  any  mechanic  putting  in  a  belt  too  small  for  the 
work  it  has  to  do,  provided  he  knows  how  much  there  is  to  do, 
which  he  ought,  somewhere  near  at  least. 


796 


HANDBOOK    ON    ENGINEERING. 


HORSE-POWER  TRANSMITTED   BY  LEATHER 
BELTS. 

DRIVING    POWER    OF    SINGLE    BELTS. 


Speed  in 
Feet  per 
Minute. 

Width  of  Belt  in  Inches. 

2 

3 

4 

5 

6 

8 

10 

12 

14 

H.  P. 

H.  P. 

H.  P. 

H.  P. 

H.  P. 

H.   P. 

H.  P. 

H.  P 

H.  P. 

400 

1 

Ij 

1 

2 

2^ 

3 

4 

5 

6 

7 

*    600 

H 

I 

3 

31 

41 

6 

71 

9 

101 

800 

2 

3 

4 

5 

6 

8 

10 

12 

14 

1,000 

21 

31 

5 

64 

71 

10 

"I 

15 

171 

1,200 

3 

4, 

7 

71 

9 

12 

15 

18 

21 

1,500 
1,800 

31 
41 

6 

6; 

92 

92 

H4 

st 

15 

18 

221 

221- 
27 

261 
311 

2,000 

5 

7- 

10 

121 

15 

20 

25 

30 

35 

2,400 

6 

9' 

12 

15 

18 

24 

30 

36 

42 

2,800 

7 

10- 

I 

14 

171 

21 

28 

35 

42 

49 

3,000 

71 

11: 

( 

15 

181 

221 

30 

371 

45 

52£ 

3,500 

81 

13 

171 

22 

26 

35 

44 

52  £ 

61 

4,000 

10 

15 

20 

25 

30 

40 

50 

60 

70 

4,500 

114 

17 

22J 

28 

34 

45 

57 

69 

78 

5,000 

121 

19 

26 

31 

371 

50 

621 

75 

87 

DRIVING   POWER   OF   DOUBLE   BELTS. 


Speed  in 
Feet  per 
Minute. 

Width  of  Belts  in  Inches. 

6 

8 

10 

12 

14 

16 

18 

20 

24 

H.  P. 

H.  P. 

H.  P. 

H.  P 

H.  P. 

H.  P. 

H.  P. 

H.  P 

H.  P. 

400 

44 

51 

74 

84 

10 

H4 

13 

144 

174 

600 

61 

81 

11 

13 

15 

174 

194 

22 

26 

800 

«! 

Hi 

141 

174 

204 

23 

26 

29 

344 

1,000 

11 

14J 

184 

214 

254 

29 

324 

36 

434 

1,200 

13 

171 

22 

26 

304 

344 

39 

44 

524 

1,500 

164 

211 

274 

324 

38 

434 

49 

544 

654 

1,800 

191 

26 

321 

39 

454 

52 

59 

654 

784 

2,000 

2l| 

29 

361 

434 

504 

58 

654 

724 

87 

2,400 

26 

341 

44 

524 

604 

694 

784 

88 

105 

2,800 

801 

401 

51 

61 

71 

81 

914 

102 

122 

3.000 

32  L 

431 

541 

654 

76 

874 

98 

108 

131 

3,500 

38 

501 

634 

76 

89 

101 

114 

127 

153 

4,000 

43^ 

584 

721 

87 

101 

116 

131 

145 

174 

4,500 

49 

65 

82 

98 

114 

131 

147 

163 

196 

5,000 

54£ 

72| 

91 

109 

127 

145 

163 

182 

218 

HANDBOOK    ON    ENGINEERING.  797 

Example.  —  Required  the  width  of  a  single  belt,  the  velocity  of 
which  is  to  be  1,500  feet  per  minute  ;  it  has  to  transmit  10  horse- 
power, the  diameter  of  the  smaller  drum  being  four  feet  with  five 
feet  of  its  circumference  in  contact  with  the  belt. 

33,000  x  10  equal  330,000,  divided  by  1,500  equal  220,  divided 
by  5  equal  44,  divided  by  6  equal  1\  inches,  the  required  width  of 
belt. 

Directions  for  calculating  the  number  of  horse  power  which  a 
belt  will  transmit.  Divide  the  number  of  square  inches  of  belt  in 
contact  with  the  pulley  by  two ;  multiply  this  quotient  by  the 
velocity  of  the  belt  in  feet  per  minute ;  again  we  divide  the  total 
by  33,000  and  the  quotient  is  the  number  of  horse-power. 

Explanations. — The  early  division  by  two  is  to  obtain  the 
number  of  pounds  raised  one  foot  high  per  minute,  half  a  pound 
being  allowed  to  each  square  inch  of  belting  in  contact  with  the 
pulley. 

Example.  —  A  six-inch  single  belt  is  being  moved  with  a 
velocity  of  1,200  feet  per  minute,  with  four  feet  of  its  length  in 
contact  with  a  three-foot  drum.  Required  the  horse-power. 

6x48  equal  288,  divided  by  2  equal  144  x  1,200  equal  172,- 
800,  divided  by  33,000  equal,  say,  5J  horse-power. 

It  is  safe  to  reckon  that  a  double  belt  will  do  half  as  much 
work  again  as  a  single  one. 

Hints  to  users  of  belts.  —  1.  Horizontal,  inclined  and  long 
belts  give  a  much  better  effect  than  vertical  and  short  belts. 

2.  Short  belts   require  to   be  tighter  than  long  ones.     A  long 
belt  working  horizontally  increases  the  grip  by  its  own  weight. 

3.  If  there   is  too  great  a  distance  between  the  pulleys,  the 
weight  of  the  belt  will  produce  a  heavy  sag,  drawing  so  hard  on 
the  shaft  as  to  cause  great  friction  at  the  bearings  ;  while,  at  the 
same  time,  the  belt  will  have  an  unsteady  motion,  injurious  to 
itself  and  to  the  machinery. 

4.  Care  should  be  taken  to  let  the  belts  run  free  and  easy,  so 


798  HANDBOOK    ON    ENGINEERING. 

as  to  prevent  the  tearing  out  of  the  lace  holes  at  the  lap  ;    it  also 
prevents  the  rapid  wear  of  the  metal  bearings. 

5.  It  is  asserted  that  the  grain  side  of  a  belt  put  next  to  the 
pulley  will  drive  30  per  cent  more  than  the  flesh  side. 

6.  To  obtain  a  greater  amount  of  power  from  the  belts  the  pul- 
leys may  be  covered  with  leather ;   this  will  allow  the  belts  to  run 
very  slack  and  give  25  per  cent  more  durability. 

7.  Leather  belts  should  be  well  protected  against  water,  oil  and 
even  steam  and  other  moisture. 

8.  In  putting  on  a  belt,  be  sure  that   the   joints  run  with  the 
pulleys,  and  not  against  them  out. 

9.  In  punching  a  belt  for  lacing,  it  is  desirable  to  use  an  oval 
punch,  the  larger  diameter  of  the  punch  being,  parallel  with  the 
belt,  so  as  to  cut  out  as  little  of  the  effective  section  of  the  leather 
as  possible. 

10.  Begin  to  lace  in  the  center  of  the  belt  and  take  care  to  keep 
the  ends  exactly  in  line  and  to  lace  both  sides  with  equal  tight- 
ness. The  lacing  should  not  be  crossed  on  the  side  of  the  belt  that 
runs  next  the  pulley.    Thin  but  strong  laces  only  should  be  used. 

11.  It  is  desirable  to  locate  the  shafting  and  machinery  so  that 
belts  shall  run  off  from  each  other  in  opposite  directions,  as  this 
arrangement  will  relieve  the  bearings  from  the  friction  that  would 
result  where  the  belts  all  pull  one  way  on  the  shaft. 

12.  If  possible,  the  machinery  should  be  so  planned  that  the 
direction  of  the  belt  motion  shall  be  from  the  top  of  the  driving  to 
the  top  of  the  driven  pulley. 

13.  Never  overload  a  belt. 

14.  A  careful  attention  will  make  a  belt  last  many  years  which 
through  neglect  might  not  last  one. 

DIRECTIONS   FOR   ADSUSTINd   BELTING. 

In  lacing-,  cut  the  ends   perfectly  square,    else  the   belt  will 
stretch  unevenly.     Make  two  rows  of  holes  in  each  end  ;   put  the 


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799 


ends  together   and  lace  with  lace  leather,  as  shown  in  Figs.  342 
and  343.     For  wide  belts,  in  addition,  put  a  thin  piece  of  leather  or 


Figs  342  and  843.    Showing  laced  joint. 

rubber  on  the  back  to  strengthen  the  joint,  equal  in  length  to  the 
width  of  the  belt,  and  sew  or  rivet  it  to  the  belt.  In  putting  on 
belting,  it  should  be  stretched  as,  tight  as  possible,  and  with  wide 
belts,  this  can  be  done  best  by  the  use  of  belt  clamps. 

HORSE  POWER  OF  BELTING. 

To  ascertain  horse-power  which  belts  will  transmit,  multiply 
width  of  'belt  ,by  diameter  of  pulley  in  inches,  by  revolutions 
of  pulley  per  minute,  by  number  in  table  corresponding  to  the 
pull  the  belt  can  exert  per  inch  of  width. 

Example. — 10"  single  horizontal  belt,  36"  pulley,  200  revolu- 
tions, pull  taken  at501bs. 

10"  x  36"  x  200  x  0.0004  =  28.8  horse-power. 

The  pulls    which    belts  1"  witle  will  transmit  are  as  follows : — 

Constant. 

Single  horizontal  belts  (pulley  same  diameter)  50  Ibs.          .0004 
Double         tfc           "      '    "    '      "           "          100  kt  .0008 

Single  vertical         "          "          "            "  40    '  .00032 

Double     "                "          "          "            "  60    4  .0005 

Single  belts  (large  to  very  small  pulleys)        .      10     '  .0001 

Double  "       *«                 '"              "  .      15    4  .00012 

Quarter  twist,  single  belts     .     .     .      0     .      .     25    '  .0002 

"         "     double     " •   „     40    '  -00032 


800  HANDBOOK    ON    ENGINEERING. 


CHAPTER     XXVIII. 
CAPACITY  OF  AIR  COHPRESSORS. 

To  ascertain  the  capacity  of  an  air  compressor  in  cubic  feet  of 
free  air  per  minute,  the  common  practice  is  to  multiply  the  area 
of  the  intake  cylinder  by  the  feet  of  piston  travel  per  minute. 
The  free  air  capacity  of  the  compressor,  divided  by  the  number 
of  atmospheres,  will  give  the  volume  of  compressed  air  per 
minute.  To  ascertain  the  number  of  atmospheres  at  any  given 
pressure,  add  15  Ibs.  to  the  gauge  pressure ;  divide  this  sum  by 
15  and  the  result  will  be  the  number  of  atmospheres.  The  above 
method  of  calculation,  however,  is  only  theoretical  and  these 
results  are  never  obtained  in  actual  practice,  even  with  com- 
pressors of  the  very  best  design  working  under  the  most  favor- 
able conditions  obtainable.  Allowances  should  be  made  for 
losses  of  various  kinds,  the  principal  losses  being  due  to  clear- 
ance spaces,  but  in  machines  of  poor  design  and  construction 
other  losses  occur  through  imperfect  cooling,  leakages  past  the 
piston  and  through  the  discharge  valves,  insufficient  area  and 
improper  working  of  inlet  valves,  etc.  In  practice  there  are  com- 
pressors where  losses  through  imperfections  and  improper  working 
conditions  range  from  15  to  25  per  cent,  while  und-er  favorable 
conditions  and  with  the  average  compressor,  the  loss  averages 
from  8  to  12  per  cent.  So  that  to  get  sufficiently  accurate 
results  in  finding  capacity  of  the  compressor,  subtract  12  per 
cent  from  above  computation,  which  gives  nearly  accurate 
figures.  The  following  table  will  be  found  useful  for  quickly 
ascertaining  the  capacity  of  an  air  compressor,  also  to  find  the 
cubical  contents  of  any  cylinder,  receiver,  etc.  The  first  column 


HANDBOOK    ON   ENGINEERING. 


801 


is  the  diam.  of  cylinder  in  inches.  The  second  shows  the  contents 
in  cubic  feet,  for  each  foot  in  length. 

Contents  of  a  Cylinder  in  Cubic  Feet  for  Each  Foot 

in  Length. 


Diam. 
Inches. 

Cubic 
Contents. 

Diam. 
Inches. 

Cubic 
Contents. 

Diam. 
Inches. 

Cubic 
Contents. 

•  OQ 

g  CD 
I  A 

51 

Cubic 
Contents. 

Diam. 
Inches 

Cubic 
Contents. 

1 

.0055 

6 

.1963 

11 

.6600 

20 

2.182 

36 

7.069 

« 

.0085 

« 

.2130 

Hi 

.6903 

204 

2.292 

37 

7.468 

ij 

.0123 

6i 

.2305 

U4 

.7213 

21 

2.405 

38 

7.886 

1| 

.0168 

.61 

.2485 

ill 

.7530 

214 

2.521 

39 

8.296 

2 

.0218 

7 

.2673 

12 

.7854 

22 

2.640 

40 

8.728 

2i 

.0276 

7* 

.2868 

12* 

.8523 

224 

2.761 

41 

9.168 

2* 

.0341 

74 

.3068 

13 

.9218 

23 

2.885 

42 

9.620 

2| 

.0413 

7| 

.3275 

13J 

.9940 

234 

2.885 

43 

10.084 

3 

.0401 

8 

.3490 

14 

1.069 

24 

3.012 

44 

10.560 

8* 

.0576 

8* 

.3713 

i« 

1.147 

25 

3.142 

45 

11.044 

3£ 

.0668 

84 

.3940 

15 

1.227 

26 

3.400 

46 

11.540 

8} 

.0767 

8| 

.4175 

15J 

1.310 

27 

3.687 

47 

12.048 

4 

.0873 

9 

.4418 

16 

.396 

28 

3.976 

48 

12.566 

« 

.0985 

9* 

.4668 

164 

.485 

29 

4.587 

f 

*l 

.1105 

n 

.4923 

17 

.576 

30 

4.909 

4| 

.1231 

9| 

.5185 

174 

.670 

31 

5.241 

5 

.1364 

10 

.5455 

18 

.767 

32 

5.585 

-5i 

.1503 

IQi 

.5730 

184 

.867 

33 

5.940 

*S 

.1650 

10£ 

.6013 

19 

.969 

34 

6.305 

5| 

.1803 

lOf 

.6303 

19^ 

2.074 

35 

5.681 

To  find  the  capacity  of  an  air-cylinder,  multiply  the  figures  in 
the  second  column  by  the  piston  travel  in  feet  per  minute.  This 
applies  to  double-acting  air  cylinders.  In  the  case  of  single- 
acting  air  cylinders,  the  result  should  be  divided  by  2. 

• 

THE  McKIERMAN   DRILL  COMPANY'S  AIR  COMPRESSOR. 

The  air -cylinder  and  water-jacket  are  one  complete  casting. 
The  heads  are  made  with  hoods  and  provision  made  for  cool  air 

in-take. " 

51 


802 


HANDBOOK    ON    ENGINEERING. 


The  atmosphere  valves  ste  bronze,  of  poppet  form.  There- 
fore, there  is  no  vacuum  and  the  cylinder  fills  absolutely  with  free 
air.  The  valves  are  closed  by  mechanical  means. 

The  discharge  valves  are  self-acting,  are  made  of  bronze.  All 
of  them  are  free  to  inspection  without  removal  or  disturbance  of 
other  parts. 

The  cooling  apparatus,  or  heat-preventing  device,  is  extremely 
effective.  Water  jacket  completely  surrounds  the  cylinder,  water 


Fig.  344.    Horizontal  single  stage  compressor. 

is  forced  to  wash  the  walls  and  is  kept  in  rapid  motion  from  bot- 
tom to  top,  from  end  to  end,  absorbing  heat  rapidly.  It  enters 
the  jacket  at  bottom,  flows  from  end  to  end,  around  partitions, 
back  and  forth  and  up.  Follows  natural  laws  in  absorbing, 
retaining  and  dispelling  the  heat  of  air. 

Regulation  of  pressure  and  speed  is  entirely  automatic.  The 
regulating  device  is  one  of  those  in  which  the  air  weighs  the 
steam  admitted  to  tte  cylinder.  Throttle  may  be  thrown  wide 
open  at  start,  then  the  regulator  takes  absolute  control,  governing 
the  speed  from  highest  to  lowest  rate,  varying  the  speed  for 


HANDBOOK    ON    ENGINEERING. 


803 


variable  amounts  of  air  which  may  be  required  and  in  such   man- 
ner as  to  keep  the  pressure  constant. 


D  ui  SBCTKM.  A<«-CiiiHUi»-ENo  ELE.ATIO*. 

>    SuovfiMi  Y*iv«». 

Fig.  345.    The  Bennett  automatic  air  compressor. 


Fig.  346.    Iiigersoll-Sergeaiit  air  compressor. 


804 


HANDBOOK    ON    ENGINEERING. 


INGERSOLL-SERGEANT  AIR  COMPRESSOR. 

This  engine,  illustrated  in  Fig.  346,  is  fitted  with  Inger- 
soll-Sergeant  air  compressor  cylinders,  and  in  connection  with 
the  Pohle  air  lift  system,  has  double  the  supply  of  water, 
using  only  one-half  the  fuel  previously  required.  The  steam 
cylinders  are  of  the  duplex  Corliss  condensing  type  and  con- 
nected tandem,  and  on  each  side  are  two  Ingersoll-Sergeant  air 
cylinders  and  two  Conover  water  cylinders.  When  the  engine 


Fig.  347.     Sectional  view  of  air  cylinder  with  vertical  lift  valves, 
class  "E"  and  "F"  compressors. 

is  in  operation,  the  air  cylinders  raise  the  water  by  the  Pohle  air 
lift  system,  from  the  wells  to  a  tank  at  the  surface,  and  from 
there  it  is  taken  by  the  water  cylinders  and  forced  to  the  stand- 
pipe.  The  cost  of  this  combination  compares  favorably  with  the 
old  plan  of  using  separate  compressors  and  water  pumps,  each 
with  their  own  steam  cylinders,  and  the  saving  in  attendance, 
friction  and  foundation  commends  its  use.  The  engines  run  at  a 
fixed  moderate  speed  and  the  regulation  of  the  air  and  water  is 
effected  by  passing  the  water  from  suction  to  discharge  when  the 
tank  is  too  low,  and  by  mechanically  unloading  the  air  cylinders 


HANDBOOK   ON    ENGINEERING.  805 

with  a  pressure  regulator  when  the  tank  is  too  full.  The  regula- 
tion is  done  mechanically,  with  floats  at  the  top  and  bottom  of  the 
receiving  tank.  This  combination  can  also  be  furnished  with 
straight  line  compressors ;  the  advantage  of  the  duplex  is  that 
should  it  be  necessary,  the  one  side  of  the  engine  can  be  discon- 
nected and  the  other  side  made  to  do  the  work. 

As  will  be  seen,  the  inlet  valves,  which  are  on  the  lower  side  of 
the  cylinder  are  offset,  thus  preventing  their  being  sucked  into 
the  cylinder  and  wrecking  the  compressor.  They  are  made  out 
of  a  solid  piece  of  steel  and  are  extremely  durable,  because  they 
are  placed  vertically,  work  in  a  bath  of  oil  and  do  not  slide  on 
their  seats.  Both  the  inlet  and  discharge  valves,  being  in 
the  cylinder,  allow  the  heads  to  be  thoroughly  water- jacketed, 
and  .this  is  an  important  feature  when  it  is  remembered  that 
the  heat  of  compression  is  greatest  at  the  end  of  the  stroke. 
The  cylinder  is,  therefore,  completely  water- jacketed.  The 
valves  are  arranged  so  that  the  air  can  be  taken  from  outside  of 
the  engine  room,  which  increases  the  efficiency  of  the  machine  8 
to  15  per  cent,  and  are  easily  accessible. 

The  two  inlet  valves  are  located  in  the  piston,  and,  with 
the  tube,  are  carried  back  and  forth  with  the  piston.  The  valve 
on  that  face  of  the  piston  which  is  toward  the  direction  of  move- 
ment is  closed,  while  the  one  on  the  other  face  is  open.  This  is 
exactly  as  it  should  be  in  order  to  force  out  the  compressed  air 
from  one  end  of  the  cylinder  while  taking  in  the  free  air  at  the 
other ;  when  the  piston  has  reached  the  end  of  its  travel  there  is, 
of  course,  a  complete  stop  while  the  engine  is  passing  the  center, 
and  an  immediate  start  in  the  other  direction.  The  valve  which 
was  open  immediately  closes  „  There  is  no  reason  for  its  remain- 
ing open  any  longer,  and  it  closes  at  exactly  the  right  time,  its 
own  weight  being  all  that  is  necessary  to  move  it.  The  valve 
on  the  other  side  is  left  behind  by  the  piston  and  the  free  air 
is  admitted  to  that  end  of  the  cylinder  for  compression  on  the 


806 


HANDBOOK    ON    ENGINEERING. 


return  stroke.  No  springs  are  used,  and  there  is  none  of  the 
throttling  of  the  incoming  air,  and  none  of  the  clattering  or 
hammering  so  noticeable  with  poppet-valves.  As  there  is  nothing 
to  make  the  valve  move  faster  than  the  piston,  it  stays  behind  until 
the  piston  stops,  leaving  the  port  wide  open  for  the  admission 


DETAILS  OF  PISTON   INLET  AIR  CYLINDER. 

A.— CircuTatfng  Water  Jnlet,  D.— Oil  Hole  for  Automatic  Oil  Cup.  G.— Piston  Inlet  Vair 
B.—Circulating  Water  Outlet.  K— Air  In  let  (through  piston  in  let pipe).  H.— Discharge  Valve, 
C.-Wat6r  Jacket  Drain  Pipe.  F.— Air  Discharge  (showi&g  flange);  }.— Water  Jacket. 

Fig.  348.    Sectional  view  of  Ingersoll-Sargeant  single 
compressor. 

of  air.  It  is  well  known  that  while  the  fly-wheel  and,  of  course, 
the  crank,  rotate  at  a  uniform  speed,  the  movement  of  the  piston 
is  not  uniform,  but  gradually  increases  in  speed  from  the  start 
till  the  crank  has  reached  half -stroke,  when  it  gradually  slows  up 
till  the  crank  is  on  the  center,  and  at  this  moment  of  full  stop 
the  valve  gently  slides  to  its  seat. 


HANDBOOK    ON    ENGINEERING. 


807 


Fig.  349.    The  Pohle  air  lift  system. 


808  HANDBOOK    ON    ENGINEERING. 

The  illustrations  on  page  807  show  the  method  of  pumping 
water  by  air.  A  compressor  in  connection  with  the  air-lift  sys- 
tem pumps  the  water  by  direct  air  pressure.  The  pump  con- 
sists of  a  water  pipe  and  an  air  pipe,  the  latter  discharging  the 
air  into  the  former  at  its  bottom,  through  a  specially  designed 
foot-piece.  The  natural  levity  of  the  air  compared  with  the 
water,  causes  it  to  rise  and,  in  rising,  to  carry  the  water  with  it 
in  the  form  of  successive  pistons,  following  one  another.  This 
system  of  pumping  has  found  a  large  range  of  application  and  is 
of  peculiar  service  in  connection  with  deep  well  pumping.  For 
this  purpose,  the  absence  of  mechanical  parts  many  feet  below 
the  surface,  offers  a  commanding  advantage.  Method  No.  1  and 
No.  2  are  almost  alike,  consisting  in  placing  the  air  and  water 
pipes  alongside  of  one  another  in  the  well,  connecting  them  at 
the  bottom  with  an  end  piece.  Method  No.  3  consists  in  placing 
a  water  discharge  pipe  into  the  well ;  the  air  passing  down  into 
the  well  through  the  annular  space  between  the  well  casing  and 
the  water  pipe.  Method  No.  4  consists  in  using  {he  well  casing 
as  the  water  discharge  pipe,  and  simply  putting  an  air  pipe  down 
into  the  well,  with  a  specially  designed  foot-piece  attached  at  the 
bottom  through  which  the  air  escapes. 


Air  Lift  Formulas. 

Height  of  Lift 
For  maximum  economy  ^  s^mersioiT    should  eQual  °-5 

125  X  Cu.  Ft.  Free  Air 
Gallons  of  water  raised  per  Mm.  =  - 


Cubic  feet  of  free  air  per  Min.  = 
Lift  in  feet  above  water  level  = 


Lift  in  Feet 
Gals,  raised  per  Min.  X  Lift 

125 
125  X  Cu.  Ft.  Free  Air 


Gals,  per  Min. 

Air  press,  required  to  start  lift  =  Submersion  +  Lift  X  -*34  4-  5 
Ratio  of  areas  of  water  pipe  to  air  pipe  =  6  to  1 


HANDBOOK   ON    ENGINEERING.  809 


CHAPTER    XXVIII.  — CONTINUED. 
THE  METRIC  SYSTEM. 

It  frequently  happens  that  an  engineer,  in  reading  books  and 
papers  devoted  to  steam  engineering,  is  confronted  with  terms 
taken  from  the  metric  system,  which  he  does  not  understand. 
We  present  a  few  of  the  metric  system  terms  most  commonly 
used,  with  their  values  in  feet  and  inches,  also,  gallons,  quarts, 
pounds,  tons,  etc. 

A  French  meter  is  39.37079  inches  long,  or  a  little  less  than 
39|  inches.  It  is  generally  taken,  —  for  convenience  in  fig 
uring,  —  at  39.37  inches. 

1  decimeter  is  -^  of  a  meter,  or,  3.937  inches  nearly. 

1  centimeter  is  T^  "         "     "       .3937     "         " 

1  millimeter  is  ^fa  "         "     "       .03937  "         " 

ALSO. 

1  decameter  equals       10  meters,  or,  32.80  feet  nearly. 
1  hectometer     "         100      "        "     328       "         " 
1  kilometer        "       1000      "        "     3280     "         " 

APPLICATION. 

1.  An  engine  shaft  is  5  meters  long,  what  is  its  length  in  feet 
and  inches?  Ans.   16  ft.  4£  ins.  nearly. 

qq  07  \s  K 

Operation  J  °"'°'*  °  =  16.4  ft.  nearly. 

MM 

2.  An   engine  cylinder   is    10.3  decimeters  in  diameter,  ho^i 
much  is  this  in  inches?  Ans.  40J  ins.  nearly 

Operation:  3.937  X  10.3  =  40.55  ins.  nearly. 


810  HANDBOOK    ON    ENGINEERING. 

3.  A  piston-rod   is  8.7  centimeters  in  diameter,  how  much  is 
this  in  inches?  Ans.  3|  ins.  nearly. 

Operation  :  -3937  X  8.7  .=  3.42  ins.  nearly. 

4.  A  chimney  is  5.1  decameters  tall,  how  much  is  this  in  feet 
and  inches?  Ans.   167  ft.  3  ins.  nearly. 

Operation :  32.80  X  5.1  =  167.28  ft. 

5.  How  many  miles  are  there  in  30.2  kilometers? 

Ans.   18-j?^  miles  nearly. 
Operation :  There  are  5280  ft.  in  a  mile. 

Then,   828°  X  80'2  =,  18.7  miles. 
5280 

6.  A  valve  has  2  millimeters  lead,  how  much  is  this  in  frac- 
tional parts  of  an  inch?  Ans.  -f-^  in.  nearly. 

Operation:  .03937  X  2  =  .07874. 
And,  .07874  X  64  =  /¥  nearly. 

7.  How  many  square  feet  in  a  circle  whose  diameter  is  one 
meter?  Ans.  8£  nearly. 

n  39,37  X  39.37  X  .7854 

Operation :  —  —  =  8.45. 

144 

8.  The  cylinder  clearance  is    1.1  cubic  decimeter,  how  many 
cubic  inches  in  the  clearance?  Ans.  67  nearly. 

Operation:  3.937  X  3.937  X  3.937  X  1.1  =  67.12+ 

ALSO. 

1  gramme  equals  15.433  grains,  or  1  ounce  nearly. 
1  kilogramme  equals  2.2047  pounds  avoirdupois. 
1  tonne  equals  1.1024  tons  of  2000  Ibs. 

ALSO. 
1  litre  equals  1.0566  quarts. 


HANDBOOK    ON    ENGINEERING.  811 


CONSEQUENTLY, 

1  U.  S.  gallon  equals  3.79  litres  nearly. 
1  U.  S.  pint  equals  .4732  litres  nearly. 

1.  A  main  shaft  weighs  800  kilogrammes,  how  much  is  this  in 
avoirdupois  pounds?  Ans.  1763J  Ibs.  nearly. 

Operation :     2.2047  X  800  =  1763.76. 

2.  An  engine  weighs  12  tonnes,  how  much  is  this  in  U.  S.  tons 
of  2000  Ibs.  each?  Ans.  13  J  tons  nearly. 

Operation:  1.1024  X  12  =  13.2288. 

3.  A  tank  contains   9000  litres  of  water,  how  much  is  this  in 
U.  S.  gallons?  Ans.  2377.35  galls. 

1.0566   X  9000 
Operation:     T~    —  Because  4  quarts  equal  1  gallon. 


THERMOMETERS. 

In  the  U«  S*  the  Fahrenheit  scale  is  the  one  in  most  common 
use,  although  in  our  laboratories  and  for  scientific  purposes  it  is 
displaced  by  the  Reaumer  and  Centigrade  scales.  Fahrenheit's 
scale  marks  the  boiling  point  by  212  degrees,  and  the  freezing 
point  by  32  degrees  above  zero. 

The  Reaumer  scale  marks  the  boiling  point  by  80  degrees,  and 
the  freezing  point  by  zero. 

The  Centigrade,  or  Celsius  scale,  marks  the  boiling  point  by 
100  degrees,  and  the  freezing  point  by  zero.  So  that,  reckoning 
from  the  freezing  point  of  Fahrenheit,  180  degrees  Fah.  equal 
80  degrees  Reaumer,  and  100  degrees  Centigrade.  Bearing  in 
mind  that  Fahrenheit's  zero  is  32  degrees  below  the  freezing  point, 
one  scale  may  readily  be  converted  into  another. 

To  convert  degs.  of  Reaumer  into  those  of  Fah. 

Rule*  —  Multiply  by  9,  divide  by  4,  and  add  32. 


812  HANDBOOK   ON    ENGINEERING. 

Example:  80    degs.  Reaumer  equals  how   many  degs.    Fah? 

Ans.  212. 
Operation:  80  X  9  =  720. 

720 

And,    1—  —  180.     Then,  180  +  32  =212. 
4 

To  convert  the  degs.  of  Centigrade  into  those  of  Fahrenheit. 
Rule*  —  Multiply  by  9,  divide  by  5,  and  add  32. 
Example:  100  degs.  Centigrade  equal  how  many  degs.   Fah.? 

Ans.  212. 
Operation:  100X9  = 


And,  180. 

o 

Then,  180+32  =  212. 

So,  also,  3  degs.  Centigrade  equal  37.2  degs.  Fahrenheit. 

Thus;   3X9  =  27.     And,    £i  =5.2.  Then,  5.2  +  32  =37.2. 


ROPE  TRANSMISSION. 

There  are  two  systems  of  rope  transmission,  the  English, 
or  multiple-rope  system,  and  the  American  or  continuous  wound 
rope  system  in  which  the  necessary  adhesion  of  rope  to  sheave  is 
obtained  by  a  tension  carriage.  We  will  treat  of  the  American  sys- 
tem only,  as  it  is  almost  universally  used  in  this  country  to  the 
exclusion  of  the  other.  One  of  the  most  common  mistakes  is  to 
lead  the  rope  to  the  tension  carriage  from  the  tight  or  pulling 
side  of  the  drive,  and  putting  on  an  abnormal  amount  of  tension 
weight  in  a  vain  endeavor  to  take  out  the  slack.  Under  the  enor- 
mous strain  of  such  an  arrangement  the  rope  wears  out  very  rap- 
idly, and  more  frequently  parts  at  the  splice.  It  is  desirable  in 
all  cases  of  rope  transmission  to  so  arrange  the  drive  that  the 
slack  side  of  the  rope  shall  be  on  the  upper  part  of  the  pulley 


HANDBOOK    ON    ENGINEERING. 


813 


thus  increasing  the  arc  of  contact,  as  the  two  sides  will  then 
approach  each  other  when  in  motion.  The  working  strain  in 
pounds  on  a  rope  should  not  exceed  200  times  the  square  of  the 
diameter  of  the  rope.  The  speed  of  the  rope  should  not  exceed 
5500  feet  per  minute,  and  this  speed  gives  the  best  results  in 
H.  P.  The  practical  limit  to  the  number  of  ropes  for  one  sheave 
cannot  be  definitely  named.  The  only  limiting  condition  is  the 
ability  of  the  tension  carriage  to  keep  up  the  slack  and  when  the 
number  of  ropes  exceeds  the  capacity  of  one  carriage,  a  second 
may  be  added  and  the  drive  made  double.  Diameters  of  sheaves 
should  not  be  less  than  40  diameters  of  the  rope,  and  50  to  60 
diameters  are  advisable,  being  justified  by  greater  length  of  life 
of  the  rope. 

HORSE  POWER  TRANSfllTTED  BY  ROPES. 

The  following  table  gives  the  horse-power  transmitted  by  a 
single  manila  rope  when  the  arc  of  contact  is  not  less  than  165 
degrees,  and  the  tension  not  greater  than  200  times  the  square  of 
the  diameter  of  the  rope. 


Velocity 

Diameter  of  Rope. 

of  Kope  in 

Feet  per 
Minute. 

5Is" 

3/4" 

1" 

ir 

IV 

11" 

2" 

1000 

1.24 

2.25 

3.57 

5.59 

8.02 

10.85 

14.20 

2000 

2.70 

3.84 

6.84 

10.68 

15.39 

20.93 

27.36 

2500 

3.30 

4.71 

8.38 

13.10 

18.86 

25.66 

33.54 

3000 

3.83 

5.46 

9.80 

15.39 

21.87 

29.74 

38.88 

3500 

4.30 

6.23 

11.09 

17.33 

24.94 

34.03 

44.35 

4000 

4.74 

6.83 

12.15 

18.98 

27.33 

37.17 

48.59 

4500 

5.01 

7.24 

12.89 

20.15 

29.00 

39.45 

51.57 

5000 

5.20 

7.47 

13.29 

20.76 

29.89 

40.65 

53.15 

5500 

5.29 

7.60 

13.53 

21.14 

30.43 

41.39 

54.11 

6000 

5.08 

7.32 

13.10 

20.36 

29.32 

39.77 

52.12 

6500 

4.74 

6.83 

12.13 

19.00 

27.34 

37.21 

48.63 

7000 

4.12 

5.93 

10.54 

16.47 

23.72 

32.26 

42.18 

7500 

3.25 

4.67 

8.32 

13.00 

18.73 

25.42 

33.23 

814 


HANDBOOK    ON    ENGINEERING. 


TO  TEST  THE  PURITY  OF  ROPE. 

A  simple  test  for  the  purity  of  manila  or  sisal  rope  is  as  fol- 
lows :  — 

Take  some  of  the  loose  fiber  and  roll  it  into  balls  and  burn 
them  completely  to  ashes,  and,  if  the  rope  is  pure  manila,  the  ash 
will  be  a  dull  grayish  black.  If  the  rope  be  made  from  sisal  the 
ash  will  be  a  whitish  gray,  and  if  the  rope  is  made  from  a  com- 
bination of  manila  and  sisal  the  ash  will  be  of  a  mixed  color. 

WIRE  ROPE  DATA. 


HOISTING    ROPE. 


PATENT  FLATTENED  STRAND. 


1 
H 

4 
l| 

2 

2* 


HERCU- 
LES. 


13.5 
22.5 
32 

40.5 

56 

67 

84 
124 
168 
211 
260 


CRUCI- 
BLE. 


I! 

5-2 


24 
30 

50" 
59J 
86 

121 

144 

182 


9 

15 

21 

29 

38 

47 

56 

81 

109 

140 

176 


4 
6 
9 
13 
17 
21 
28 
40 
54 
66 
75 


19    WIRE    ROUND    STRAND. 

03 

HEKCU- 
LES. 

CKUCI-      | 
BLE. 

IRON. 

w 

•Q 

oo 

Dd 

O 

fl 

0 

fl     . 

o 

fl    . 

0 

**' 

^£ 

£5 

o   . 

22 

£  fl 

M 

»s 

5   go 

AS 

•2  a- 

&•§ 

fl"s 

B 

ga 
SI 

IP 

1" 

IP" 

03  * 

IH 

cu 

IP 

1 

16J 

"5 

12.5 
20 

11 

14 

8.8 
13  6 

8 
12 

6 

1 

30 

29 

18 

19.4 

16 

9 

1 

39 

36 

23 

26 

20 

13 

1 

a 

50 
60 

30 

38 

34 
42 

26 
33 

17 
21 

ij 

71 

77 

46 

50 

40 

25 

Ji 

103 

113 

66 

72 

57 

36 

11 

147 

157 

93 

96 

80 

48 

2 

172 

191 

111 

124 

92 

62 

2* 

218 

238     1 

142 

156 

117 

74 

HANDBOOK    ON    ENGINEERING.  815 


ALTERNATING  CURRENT  MACHINERY. 

CHAPTER     XXIX. 
THE  PRINCIPLES  OF  ALTERNATING  CURRENTS. 

The  actions  of  alternating  currents  are  not  so  easily  under- 
stood as  those  of  continuous  currents  and  to  most  men  not 
familiar  with  the  subject  they  appear  to  be  a  mystery  that  can 
only  be  fathomed  by  those  who  are  well  versed  in  the  higher 
branches  of  mathematics.  As  a  matter  of  fact,  when  we  once 
get  on  the  right  track,  alternating  current  actions  present  no  more 
difficulty  to  the  man  of  fair  mental  ability,  who  is  willing  to  work 
to  learn,  than  the  more  simple  continuous  current  actions.  What 
makes  alternating  currents  difficult  to  understand  is,  that  in  con- 
sequence of  the  ever-changing  strength  of  the  current,  inductive 
actions  are  developed  that  react  upon  the  current  itself  so  that  it 
becomes  impossible  to  determine  the  magnitude  of  the  current, 
the  e.m.f .  or  the  energy  flowing  in  the  circuit  by  the  simple  rules 
used  for  continuous  currents.  As  the  strength  of  an  alternating 
current  is  constantly  changing  the  magnitude  of  the  inductive 
actions  is  constantly  changing,  and  this  fact  further  increases 
the  difficulty  of  the  subject. 

In  studying  the  principles  of  continuous  currents  we  learn  that 
when  a  conductor  is  moved  across  a  magnetic  field  an  e.m.f.  is 
developed  in  it ;  arid  thus  we  understand  the  operation  of  a  gen- 
erator, as  we  know  that  when  the  armature  revolves,  it  carries 
the  conductors  upon  its  surface  through  the  magnetic  flux  that 
issued  from  the  poles  of  the  field.  We  further  learn  that  inas- 


816  HANDBOOK   ON   ENGINEERING. 

much  as  the  magnitude  of  the  e.m.f .  is  increased  by  increasing 
the  strength  of  the  magnetic  flux,  or  the  number  of  conductors 
on  the  armature  or  the  velocity  of  rotation',  that  one  or  all  these 
factors  must  be  increased  to  increase  the  voltage.  Thus  we  come 
to  consider  that  to  induce  a  high  e.m.f.  we  must  have  a  strong 
magnetic  field.  Now  one  of  the  first  things  that  the  student  of 
alternating  currents  finds  out  is  that  in  an  alternating  current 
circuit,  the  strongest  e.m.f.  induced  by  the  action  of  the  current 
itself,  comes  at  the  very  time  when  the  magnetic  field  is  the 
weakest,  and  this  appears  to  him  to  completely  upset  all  the 
principles  of  continuous  currents ;  but  in  reality  it  does  not. 
To  be  able  to  get  over  this  stumbling  block  successfully  it  is 
necessary  to  realize  that  the  magnitude  of  the  e.m.f.  induced  in 
a  conductor  that  is  moved  through  a  magnetic  field  is  not  depend- 
ent upon  the  strength  of  the  magnetic  field,  but  upon  the  rate, 
or  rapidity  with  which  the  conductor  cuts  the  magnetic  flux. 
Now  it  so  happens  that  in  a  continuous  current  generator,  the 
rapidity  with  which  the  conductors  cut  the  magnetic  flux  increases 
with  increase  in  the  strength  of  the  magnetic  field,  or  the  velocity 
of  rotation,  and  thus  it  comes  about  that  in  this  case,  the  increase 
in  the  induced  e.m.f.  appears  to  be  due  to  increase  in  armature 
velocity  or  field  strength  when  in  reality  it  is  due  to  increase  in 
the  rate  at  which  the  conductors  cut  through  the  magnetic  flux. 
The  magnetic  flux  developed  by  an  alternating  current  alternates 
precisely  as  the  current  does,  and,  as  will  be  clearly  explained 
presently,  this  magnetic  flux  cuts  through  any  conductors  in  its 
path,  and  the  rate  at  which  it  cuts  them  is  the  greatest  at  the  in- 
stant when  the  direction  of  the  flux  is  changing,  and  this  is  the 
instant  when  the  flux  is  nothing,  so  that  the  e.m.f.  induced  by 
the  magnetic  flux  developed  by  an  alternating  current  is  the 
greatest  at  the  very  instant  when  the  magnetic  field  has  a  zero 
strength.  The  foregoing  facts  can  be  made  more  clear  by  refer- 
ence to  diagrams. 


HANDBOOK    ON    ENGINEERING. 


817 


Fig-*  350  is  a  simple  diagram  that  can  be  taken  to  represent  a  gen- 
erator, either  of  continuous  or  alternating  currents.  The  dark  circles 
A  A,  B  B  and  G  G  represent  the  sides  of  three  loops  of  wire 
which  may  be  regarded  as  wound  upon  the  surface  of  an  armature. 


Figs.  350  and  851.    Principle  of  electric  generator. 

The  vertical  lines  represent  a  magnetic  flux  passing  between  the 
field  poles  Pand  N.  If  the  armature  upon  which  the  three  loops 
are  mounted  is  rotated,  e.m.fs.,  will  be  induced  in  each  one  of 
the  loops,  but  the  magnitude  of  these  e.m.fs.  will  not  be  the 
same.  If  we  take  the  instant  when  the  loops  are  in  the  position 
shown,  the  e.m.f .  in  A  A  will  be  zero,  while  that  in  G  G  will  be 
the  highest  and  that  in  B  B  will  be  seven-tenths  of  that  in  G  G. 
Now  all  these  coils  rotate  at  the  same  velocity  being  mounted  upon 
the  same  armature,  and  all  move  through  a  magnetic  field  of  the 
same  strength,  yet,  in  A  A  no  e.m.f.  is  developed  while  in  B  B  the 
e.m.f.  is  only  seven-tenths  of  that  developed  in  G  (7.  The 
question  is,  why  this  difference?  The  answer  is,  that  while  loops 
A  A  move  just  as  fast  as  G  G  they  do  not  cut  the  magnetic  flux 

52 


818  HANDBOOK    ON    ENGINEERING. 

because  they  are  moving  in  a  direction  parallel  with  the  lines  of 
force,  the  vertical  lines,  hence,  the  rate  at  which  the  magnetic 
flux  is  cut  by  them  is  zero,  therefore  the  e.m.f .  developed  is  zero. 
In  B  B  the  e.m.f.  is  seven-tenths  of  that  developed  in  G  (7, 
because  the  sides  of  this  loop  are  moving  in  a  direction  that  is 
not  directly  across  the  magnetic  flux,  but  forms  an  angle  of  45 
degrees  with  it,  so  that  their  actual  velocity  in  a  direction  parallel 
with  A  A  is  seven-tenths  of  the  velocity  of  G  0  in. this  same 
direction. 

From  the  foregoing  it  will  be  seen  that  when  we  get  down  to 
a  close  examination  of  Fig.  350  we  find  that  the  magnitude  of 
the  e.m.f.  developed  in  the  several  loops  is  directly  proportional 
to  the  rate  at  which  the  sides  of  the  loop  cut  through  the 
magnetic  flux. 

Let  us  now  consider  Fig.  35 1.  In  this  diagram,  circle  A  repre- 
sents a  wire,  seen  end  on,  through  which  an  alternating  current  is 
flowing.  An  alternating  current  is  one  that  flows  first  in  one 
direction,  and  then  in  the  opposite  direction,  and  continues 
changing  the  direction  in  which  it  flows  at  regular  intervals  of 
time.  Now  it  is  self-evident  that  if  a  current  flows  through  a 
wire  in  alternate  directions,  it  must  stop  flowing  in  one  direction 
before  it  can  flow  in  the  opposite  direction,  that  is  at  the  instant 
when  the  direction  of  flow  is  changing,  there  can  be  no  current. 
Such  being  the  case,  when  the  current  begins  to  flow  in  either 
direction,  it  must  increase  in  strength  gradually  up  to  a  certain 
point,  and  then  begin  to  decrease,  so  as  to  reduce  to  nothing  at 
the  instant  when  the  direction  of  flow  changes.  As  is  explained 
in  the  section  on  continuous  currents,  when  a  current  of  elec- 
tricity flows  through  a  wire,  a  magnetic  flux  is  developed  around 
the  wire  and  this  can  be  represented  by  lines  of  force  drawn  in 
the  form  of  circles,  as  in  Fig.  351.  If  there  is  no  current  flowing 
through  the  wire  there  is  no  magnetic  flux,  therefore,  if  we 
consider  the  instant  when  a  current  begins  to  flow,  we  can  imagine 


HANDBOOK    ON    ENGINEERING.        .  819 

that  at  this  instant  the  magnetic  flux  begins  to  expand  outward 
from  the  wire,  and  since  the  circular  lines  are  drawn  to  represent 
this  flux  we  can  assume  that  these  expand  outward,  like  the  rip- 
ples on  the  surface  of  a  pond  when  a  pebble  is  thrown  into  the 
water.  So  long  as  the  current  flowing  through  the  wire  increases 
in  strength,  just  so  long  will  the  magnetic  circles  of  force  expand, 
but  when  the  current  reaches  its  greatest  strength  the  circular 
lines  of  force  will  become  stationary,  and  will  remain  so  if  the 
current  remains  at  its  maximum  strength ;  but  if  the  current 
begins  to  reduce  in  strength  as  soon  as  it  reaches  its  maximum, 
then  the  circular  lines  of  force  will  begin  to  contract  immediately 
after  they  stop  expanding,  just  as  a  swing  will  begin  to  move 
backward  the  instant  it  stops  swinging  forward. 

If  the  circles  B  and  G  in  Fig.  351  represent  two  wires  parallel 
with  A,  it  is  evident  that  the  magnetic  circles  of  force  when  they 
move  outward  from  A  will  cut  through  B  and  C  in  one  direction, 
and  when  they  contract  back  upon  A  they  will  cut  through  these 
two  wires  in  the  opposite  direction.  When  these  circular  lines 
of  force  cut  through  the  wires  B  G  they  will  induces. m.fs.  in  the 
latter,  and  if  these  e.m.fs.  are  positive  when  the  lines  of  force  ex- 
pand, they  will  be  negative  when  the  lines  contract.  When  the 
current  reaches  its  maximum  strength  and  the  circular  lines  of 
force  become  stationary  for  an  instant,  they  will  not  cut  the  wires 
B  and  C  and  at  this  instant  there  will  be  no  e.m.f.  induced  in 
these  wires.  Now  the  circular  lines  of  force  become  stationary 
at  the  very  instant  when  the  current  flowing  through  the  wire 
reaches  its  greatest  strength  and  is  on  the  point  of  reducing,  so 
that  at  this  instant  the  e.m.f.  induced  in  the  wires  B  and  C  is  zero 

The  highest  e.m.f.  induced  in  B  and  C  occurs  at  the  instant 
when  the  current  flowing  through  A  is  changing  its  direction,  or,  in 
other  words,  at  the  instant  when  there  is  no  current.  Just 
before  the  current  reduces  to  zero,  the  circular  lines  of  force 
are  contracting  upon  wire  A,  and  the  instant  after  the  cur- 


820  HANDBOOK    ON    ENGINEERING. 

rent  reduces  to  zero  and  changes  its  direction,  tlKse  lin?s 
of  force  will  be  expanding  so  that  in  the  first  case  the  lines 
of  force  will  sweep  over  wires  B  and  0  in  a  direction  toward 
A,  and  in  the  second  case  they  will  sweep  over  these  wires  in  a 
direction  away  from  A.  From  this  fact  it  might  be  inferred  that 
the  e.m.f.  induced  in  the  two  cases  would  be  in  opposite  direc- 
tions, but  this  is  not  so,  owing  to  the  fact  that  the  lines  of  force 
change  in  direction  when  the  current  changes,  so  that  if  while 
contracting  they  are  directed  clockwise,  as  soon  as  they  begin  to 
expand  they  will  be  directed  counter  clockwise.  As  a  result  of 
this  change  in  the  direction  of  the  lines  of  force  when  they  change 
from  contracting  to  expanding,  the  e.m.fs.  induced  in  B  and  C 
are  in  the  same  direction  before  the  lines  stop  contracting  and 
after  they  begin  to  expand.  The  circular  lines  of  force  stop  con- 
tracting and  begin  to  expand  at  the  same  instant,  so  that  the 
inductive  action  developed  by  the  contracting  lines  is  followed  up 
without  a  break  by  the  expanding  lines.  In  alternating  currents 
such  as  are  actually  used  in  practice,  the  rate  at  which  the 
strength  of  the  current  changes  is  the  greatest  when  it  is  just 
beginning  to  grow,  and  when  it  is  reduced  almost  to  zero,  and  on 
this  account  the  highest  e.m.f.  induced  in  wires  B  and  G  occurs 
at  the  instant  when  the  direction  of  the  current  is  changing,  that 
is,  when  the  current  is  zero.  Alternating  currents  can  be  de- 
veloped in  which  the  rate  of  change  in  the  current  is  not  the 
greatest  just  when  they  begin  to  grow  and  when  they  are  reduced 
nearly  to  zero  and  with  such  currents  the  highest  e.m.f.  induced 
in  wires  B  and  0  would  not  come  at  the  instant  when  the  current 
is  zero,  but  would  come  at  the  instants  when  the  change  in  the 
current  is  the  most  rapid. 

In  every  kind  of  alternating  current,  however,  the  instant  when 
the  e.m.f.  induced  in  B  and  C  is  zero  is  the  instant  when  the 
current  reaches  the  maximum  value,  and  begins  to  decrease, 
for  this  is  the  only  instant  when  the  circular  lines  of  force  are 


HANDBOOK    ON    ENGINEERING. 


821 


immovable ;  it  being  the  instant  when  they  are  about  to  change 
from  expanding  to  contracting,  while  still  flowing  in  the  same 
direction.  When  the  current  becomes  zero,  the  lines  of  force 
change  from  contracting  to  expanding  but  at  this  instant  they 
also  change  their  direction  so  that  the  new  expanding  circular 
lines  of  force  take  up  the  work  if  inducing  an  e.m.f.  in  the  wires 
B  and  (7  at  the  very  point  where  the  contracting  lines  leave  off. 

The  circular  lines  of  force  developed  by  the  current  flowing 
in  A,  cut  through  this  wire  as  well  as  through  B  and  (7,  hence, 
they  induce  an  e.m.f.  in  A;  that  is  an  alternating  current  induces 
an  e.m.f.  in  its  own  circuit  as  well  as  in  adjoining  circuits.  The 
action  upon  adjoining  wires  is  called  mutual  induction,  and  that 
upon  its  own  wire  is  called  self-induction.  These  e.m.fs.  act  in 
a  direction  opposite  to  that  of  the  current  that  induces  them. 

The  relations  between  alternating  currents  and  e.m.fs.  can  be 
shown  by  means  of  diagrams,  the  simplest  of  which  are  con* 


Fig.  352.    Relation  between  current  and  electro- motive  force* 

structed  in  the  manner  shown  in  Fig.  352.  In  diagrams  of  this 
type  the  line  0  T  represents  time,  thus  if  a  point  is  assumed  to 
move  from  0  in  the  direction  of  T  at  a  uniform  velocity  of  say 
one  foot  per  second,  then  a  length  of  one  inch  will  represent  an 
interval  of  time  of  one-twelfth  of  a  second.  Distances  measured 
in  the  vertical  direction,  along  0  S  represent  the  magnitude  of 


822  HANDBOOK   ON   ENGINEERING. 

the  current  or  e.m.f.  Positive  currents  and  e.m.f.  are  indicated 
above  the  time  line  0  T  and  negative  currents  and  e.m.fs.  below 
this  line.  Thus  the  wave  line  A  A  A  can  represent  an  alternating 
current  or  e.m.f.  or  an  alternating  magnetic  flax.  This  curve  it 
will  be  seen  is  above  0  T  from  0  to  6,  and  below  0  Tfrom  b 
to  d,  being  again  above  from  d  to  T.  The  two  sections  of  the 
curve  from  0  to  d  constitute  one  cycle,  or  two  alternations.  The 
portions  between  the  lines  0  a,  a  6,  b  c,  c  d  are  called  quarter 
cycles  or  quarter  periods.  The  time  from  O  to  d  is  called  one 
period,  and  if  this  is  equal  to  one-tenth  of  the  distance  that 
represents  one  second,  then  there  are  ten  periods  to  one  second. 
This  fact  is  indicated  by  saying  that  the  periodicity  of  the  current 
is  ten,  or  that  its  frequency  is  ten.  The  frequency  of  alternating 
currents  in  common  use  ranges  between  20  and  130. 

The  curve  A  A  in  Fig.  352  represents  a  current  or  e.m.f.  that 
increases  or  decreases  at  a  certain  rate,  but  for  a  current  varying 
at  some  other  rate  it  would  be  necessary  to  use  a  curve  of  differ- 
ent shape  to  correctly  represent  it.  Thus  if  the  current  does  not 
increase  so  fast  when  rising  from  the  zero  value,  but  increases 
faster  when  nearing  its  maximum  value  we  will  require  a  modifica- 
tion of  the  curve  such  as  is  indicated  by  B,  in  which  the  slope  is 
more  gradual  on  the  start,  and  near  the  middle  becomes  more 
steep.  If  on  the  other  hand  the  current  increases  more  rapidly 
on  the  start,  and  less  rapidly  as  it  approaches  the  maximum  value, 
we  will  have  to  use  a  curve  something  like  C  which  is  steeper  at 
the  ends  and  flatter  at  the  middle. 

The  actual  form  of  curve  required  to  correctly  represent  an 
alternating  current  depends  upon  the  rate  at  which  the  current 
varies,  and  this  rate  depends  upon  the  construction  of  the  machine 
in  which  it  is  generated.  For  the  purpose  of  simplifying  calcula- 
tions it  is  necessary  to  assume  that  the  rate  of  variation  of  a  cur- 
rent is  such  that  it  can  be  represented  in  a  diagram  such  as  Fig* 
352  by  some  form  of  curve  that  can  be  drawn  in  accordance  with 


HANDBOOK    ON    ENGINEERING. 


823 


some  fixed  rule.  The  curve  A  A  is  of  circular  form,  but  there 
are  few  alternating  current  generators  that  develop  currents  that 
such  a  curve  can  properly  represent. 

If  a  current  alternates  in  equal  intervals  of  time,  and  the  rate 
of  variation  is  the  same  when  it  is  flowing  negatively  as  when  it  is 
flowing  positively,  then  it  can  be  represented  by  a  curve  that  is 
of  symmetrical  construction,  such  as  A  A  in  which  the  intervals  of 
time  0  &,  b  d  are  equal  and  the  curves  above  the  line  0  T  are  of 
the  same  shape  as  those  below  it.  Such  a  current  is  called  a 
symmetrical  periodic  current,  and  it  is  the  only  kind  with  which  we 
have  to  do  in  practice.  It  can  be  readily  understood,  however, 
that  the  current  can  be  far  from  regular,  that  is,  the  time  during 
which  it  flows  positively  can  be  more  or  less  than  the  time  during 
which  it  flows  negatively,  and  the  rate  of  variation  in  the  two 


0 

& 


Fig.  353.    Irregular  periodic  curve. 

instances  can  be  different.  The  curves  in  Figs  353  and  354  illus- 
trate currents  of  this  kind.  In  Fig.  353  the  positive  impulses  of 
the  current  are  longer  than  the  negative,  as  is  shown  by  the  greater 
length  of  lines  0  a,  b  c  as  compared  with  a  b.  It  will  also  be 
seen  that  the  rate  of  variation  is  different  as  is  indicated  by  the 
difference  in  the  form  of  the  portions  A  A  and  B  B  of  the 
curve.  In  Fig.  354  the  irregularity  is  still  greater,  as  all  the  time 
intervals  Oa,  a  &,  &  c,  c  d,  are  different,  as  are  also  the  portions 
A  B  C  D  E  of  the  curve. 


824 


HANDBOOK    ON    ENGINEERING. 


The  alternating  currents  developed  by  alternating  current 
generators  have  such  a  rate  of  variation  that  they  can  be  repre- 
sented in  diagrams  by  means  of  what  is  known  as  a  sine  curve. 


s 


Tig.  354.    Showing  still  greater  irregularity. 


Tnis  curve  is  not  a  perfectly  true  representation  of  practical 
alternating  currents,  but  it  comes  so  near  to  it  that  calculations 
I  M,sed  upon  the  assumption  that  the  sine  curve  represents  the  actual 


a  a, 


ff 


\ 


Fig.  355.     Construction  of  sine  curve. 


variation,  do  not  depart  from  the  truth  by  more  than  two  or  three 
per  cent,  and  in  some  cases  less  than  that.  As  the  sine  curve  is 
commonly  used  to  represent  alternating  currents  we  will  show 


HANDBOOK   ON   ENGINEERING.  825 

how  it  is  constructed  by  the  aid  of  Fig.  355.  In  this  diagram  dia- 
metrical lines  a  b  c  are  drawn  on  the  circle  B,  dividing  it  into 
any  desired  number  of  equal  parts.  A  distance  0  T  on  the  hor- 
izontal line  is  divided  into  an  equ^l  number  of  equal  parts  and 
perpendicular  lines  a  a  are  drawn  at  these  divisions.  From  the 
points  where  the  lines  a  b  c  cut  the  circle  lines  are  drawn  parallel 
with  0  T  as  shown  at  e  f  g  and  the  points  where  these  cut  the 
corresponding  perpendicular  lines  a  a  form  points  of  the  sine 
curve  A  A.  The  distance  O  T  can  be  made  anything  desired 
without  affecting  the  character  of  the  curve,  the  only  difference 
being  that  if  it  is  short  the  curve  will  be  more  pointed  than  if  it 
is  long. 

One  reason  why  it  is  assumed  that  alternating  currents  vary 
in  accordance  with  a  sine  curve  is  that  if  the  variation  is  at  this 
rate  the  e.m.f .  induced  by  the  magnetic  flux  developed  by  the 
current  will  also  vary  in  accordance  with  the  sine  curve,  so  that 
the  current,  the  magnetization  and  the  induced  e.m.f.  can  be  rep- 
resented by  sine  curves,  and  thus  the  process  of  calculating  the 
effect  of  the  induced  e.m.f.  upon  the  strength  of  the  current  can 
be  greatly  simplified. 

By  looking  at  Fig.  350  it  can  be  seen  at  once  that  if  the 
loop  A  A  is  revolved  at  a  uniform  velocity,  and  the 
magnetic  field  between  the  poles  P  and  N  is  of  uniform 
strength  at  every  point,  the  e.m.f.  induced  in  A  A  will 
vary  in  strict  accordance  with  the  variations  of  the  sine 
curve  A  A  of  Fig.  355,  for  in  the  position  A  A  the  e.m.f.  will  be 
zero,  and  in  position  G  C  it  will  be  the  maximum,  while  in  any  in- 
termediate position  such  as  B  B  it  will  be  equal  to  the  actual  velocity 
of  the  sides  of  the  loop  measured  in  the  direction  parallel  with 
AA  ,  and  this  velocity  is  equal  to  the  distance  of  the  side  of  the 
loop  from  the  horizontal  line  A  A.  Now  the  height  of  the  sine 
curve  A  A  in  Fig.  355  at  any  point  is  also  equal  to  the  distance  from 
the  end  of  the  corresponding  line  in  circle  B  from  the  horizontal 


826 


HANDBOOK   ON   ENGINEERING. 


line,  that  is,  the  distrance  e  e'  from  the  horizontal  line  to  the  curve 
is  the  same  as  the  distance  e  e  on  the  circle. 

The  complete  sine  curve  from  0  to  T  is  traced  by  following  the 
rotation  of  the  radius  of  the  circle  through  one  complete  revolu- 
tion. On  that  account  this  distance  0  T  is  taken  to  represent  one 
revolution,  and  is  divided  into  360  degrees,  the  same  as  the 
circle.  Half  the  distance,  or  0  d,  is  equal  to  180  degrees,  and 
one-quarter  the  distance  is  90.  The  vertical  lines  a  a  in  Fig.  355 
are  30  degrees  apart. 

The  way  in  which  sine  curves  are  used  to  represent  alternat- 
ing currents  and  e.m.fs.  is  shown  in  Fig.  356.  In  this  diagram, 


a 


Fig.  356.    Manner  of  indicating  alternating  currents. 

let  the  curve  A  represent  an  alternating  current  flowing  through  a 
wire.  As  is  fully  explained  in  the  foregoing,  this  current  will 
develop  an  alternating  magnetic  flux,  and  this  flux  will  increase 
and  decrease  as  the  current  increases  and  decreases,  that  is,  it 
will  keep  in  time  with  the  current,  or  in  step  with  it,  as  it  is  com- 
monly expressed.  Such  being  the  case,  the  curve  A  can  be  used 
to  represent  the  magnetic  flux  as  well  as  the  current,  providing 
we  assume  a  proper  scale  for  both.  Looking  at  the  half  circle  to 
the  left  of  the  figure,  it  will  be  seen  that  curve  A  is  described  by 


HANDBOOK   ON   ENGINEERING.  827 

a  radius  rotating  around  the  middle  circle.  Remembering  what  was 
said  in  connection  with  Fig.  351  as  to  the  time  relation  between  the 
magnetic  flux  and  the  e.m.f .  induced  thereby,  we  will  realize  that 
at  the  instant  0  when  the  flux  is  zero,  the  induced  e.m.f.  must 
be  at  the  maximum  value,  and  it  will  act  in  opposition  to  the 
e.m.f.  that  drives  the  current  through  the  wire,  hence,  in  the 
diagram,  it  will  have  to  be  drawn  below  line  0  T.  Let  the  maxi- 
mum value  of  this  induced  e.m.f.  be  equal  to  0  c,  then  for  all 
other  values  it  will  be  correctly  represented  by  the  sine  curve  .B, 
which  is  traced  by  the  rotation  of  the  radius  of  the  inner  circle. 

At  the  instant  of  time  0,  the  magnetic  flux  is  zero,  hence  the 
radius  of  the  middle  circle  from  which  curved  is  traced  must  be 
in  the  direction  of  line  0  T.  At  this  same  instant  the  induced 
e.m.f.  is  at  the  maximum  value  hence  the  radius  that  traces 
curve  B  must  be  in  the  vertical  position  parallel  with  O  c.  From 
this  we  see  that  in  relation  to  time  the  curves  A  and  B  that  repre- 
sent the  magnetic  flux  and  the  induced  e.m.f.  are  one-quarter  of 
a  cycle  apart,  that  is  the  induced  e.m.f.  is  90  degrees  behind  the 
magnetization,  and  also  90  degrees  behind  the  current  that  flows 
through, the  wire. 

No  kind  of  electric  current,  whether  continuous  or  alternating, 
can  flow  through  a  circuit  unless  there  is  an  e.m.f.  to  drive  it, 
and  this  e.m.f.  must  be  sufficient  to  impel  the  current  against 
all  resistances  of  any  kind  that  it  may  encounter.  The  e.m.f. 
that  impels  a  current  through  an  alternating  current  circuit  is 
called  the  impressed  e.m.f.  In  Fig.  356  it  is  evident  that  the 
impressed  e.m.f.  must  be  sufficient  not  only  to  overcome  the 
actual  resistance  that  opposes  the  flow  of  the  current  represented 
by  curve  -4,  but  also  sufficient  to  overcome  the  opposing  action  of 
the  induced  e.m.f.  represented  by  curve  B.  Now  the  e.m.f. 
required  to  overcome  the  resistance  that  opposed  the  flow  of  the 
current  can  be  represented  by  the  curve  -4,  in  precisely  the  same 


828  HANDBOOK   ON   ENGINEERING. 

way  as  this  curve  represents  the  magnetization  ;  hence,  the  curve 
G  which  represents  the  impressed  e.m.f.  must  at  every  point  be 
equal,  in  height,  from  the  line  0  T,  to  the  sum  of  the  heights  of  the 
curves  A  and  B,  when  these  two  curves  are  on  opposite  sides 
of  0  T,  or  to  their  difference  when  they  are  on  the  same  side.  At 
the  instant  0  it  is  clear  that  as  the  current  is  zero,  the  impressed 
e.m.f.  C  must  be  of  the  value  0  c'  to  balance  the  induced  e.m.f. 
B  for  if  it  were  not,  there  would  be  a  current  flowing  negatively 
under  the  influence  of  e.m.f.  B.  At  any  instant  between  O  and 
d,  the  impressed  e.m.f.  C  must  be  equal  to  the  sum  A  and  B,  that 
is,  the  distance  from  G  to  the  time  line  0  T  must  be  equal  to  the 
distance  between  the  curves  ^4  B  measured  on  the  same  vertical  line. 
At  the  instant  d  the  induced  e.m.f.  is  zero,  hence  the  impressed 
e.m.f.  is  equal  to  the  distance  of  curve  A  above  line  0  T.  For 
any  interval  of  time  between  d  and  e,  the  impressed  and  the  in- 
duced e.m.fs.  are  acting  together,  so  that  the  first  named,  that  is, 
curve  (7,  need  only  be  equal  to  the  difference  between  A  and  B. 

By  studying  the  diagram  Fig.  356  it  will  be  seen  that  the  curve 
(7,  which  represents  the  impressed  e.m.f.,  is  described  by  the 
rotation  of  the  radius  of  the  outer  circle  at  Z),  and  in  order  that 
this  e.m.f.  may  have  the  value  of  0  cf  at  the  instant  0,  it  is  nec- 
essary for  the  describing  radius  at  this  instant  to  be  in  the  posi- 
tion b.  From  this  it  will  be  seen  that  the  impressed  e.m.f.  is  not 
in  time  with  the  current  but  in  advance  of  it  by  a  time  interval 
that  is  equal  to  the  angle  formed  by  the  radius  b  with  the  line 
0  T. 

If  two  alternating  currents,  e.m.f.  or  magnetic  fluxes  are 
in  time  with  each  other  they  are  said  to  be  in  phase,  but  if  they 
are  not  in  time  they  are  out  of  phase.  In  Fig.  356  the  current,  the 
impressed  e.m.f.  and  the  induced  e.m.f.  are  out  of  phase  with  each 
other.  The  impressed  e.m.f.  leads  the  current,  and  the  latter 
leads  the  induced  e.m.f.  This  relation  is  also  expressed  by  say 


HANDBOOK    ON    ENGINEERING. 


829 


ing  that  the  current  lags  behind  the  im- 
pressed e.m.f.  and  the  induced  e.m.f. 
lags  behind  the  current.  The  current 
and  the  impressed  e.m.f.  can  never  be 
out  of  phase  by  an  angle  as  great  as  90 
degrees,  but  the  phase  difference  can  be 
any  angle  less  than  this.  The  induced 
e.m.f.  is  always  90  degrees  out  of  phase 
with  the  current.  The  induced  e.m.f. 
in  the  circuit  in  which  the  current  flows 
is  called  the  self-induction. 

The  relations  between  the  impressed 
e.m.f.,  the  current  and  the  self-induc- 
tion both  in  magnitude  and  phase  are 
clearly  shown  in  Fig.  357,  which  is 
simply  an  enlarged  view  of  the  left  side 
of  Fig.  356.  The  radius  A  of  the  outer 
circle  is  the  impressed  e.m.f.  The 

radius  B  of  the  middle  circle  is  the  cur- 
Fig.  357.  Enlarged  Yiew 

of  Fig.  356.  rent,    and   the   radius   C  of  the   inner 

circle  is  the  self-induction.  The  magnitude  of  any  one  of  these 
three  quantities  at  any  instant  of  time  is  equal  to  the  distance 
from  the  end  of  the  line  to  the  horizontal  line.  The  radius  B 
which  represents  the  current  is  on  the  horizontal  line,  hence  the 
current  at  the  instant  represented  by  the  diagram  is  zero.  The 
self-induction  C  has  a  value  at  this  instant  equal  to.  the  length  of 
the  line,  that  is,  it  is  at  the  maximum  value,  and  as  it  is  below 
the  horizontal  line  it  is  negative.  The  impressed  e.m.f.  A,  has 
the  value  of  a  a,  and  being  above  the  horizontal  line,  it  is  positive. 
The  phase  relation  and  also  the  magnitude  of  these  quantities  is 
also  shown  in  Fig.  358,  which  is  constructed  from  Fig.  357  by  remov- 
ing the  self-induction  to  the  position  of  line  a  a.  From  Fig.  358  it 


830 


HANDBOOK    ON    ENGINEERING. 


CURRENT. 


can  be  seen  that  if  we  know  two 
of  the  quantities  we  can  always 
determine  the  other  one  by  sim- 
ply constructing  a  right  angle 
triangle. 

The  self-induction  acts  to 
oppose  the  flow  of  current, 
hence  it  is  equivalent  to  the 
addition  to  a  certain  amount  of 
resistance  to  the  circuit,  but  as 
can  be  seen  from  the  diagrams 
it  cannot  be  added  directly, 
after  the  fashion  in  which 
numbers  are  added.  To  add  it 
properly  it  must  be  placed  at 
right  angles  to  the  resistance. 

If  the  self-induction  is  divided 
by  the  strength  of  the  current, 
we  get  a  quantity  that  can  be 
compared  with  the  resistance, 
and  this  quantity  is  called  the 


RESISTANCE. 

Figs.  858  and  859.    Illustrating 

resistance,    reactance    and 

impedance. 

reactance  and  is  measured  in  ohms  precisely  as  the  resistance  is. 

The  flow  of  current  in  a  continuous  current  circuit  is  opposed 
by  the  resistance  only,  but  in  an  alternating  current  circuit  it  is 
opposed  by  the  resistance  and  the  reactance  and  the  combined 
effect  of  these  two  is  called  the  impedance  of  the  circuit. 

The  relation  between  resistance,  reactance  and  impedance  is 
the  same  as  that  between  impressed  e.m.f.,  current  and  self- 
induction,  and  is  shown  in  Fig.  359. 

The  reactance  multiplied  by  the  current  gives  the  self -induction. 

The  impedance  multiplied  by  the  current  gives  the  impressed 
e.m.f. 


HANDBOOK    ON    ENGINEERING. 


831 


The  resistance  multiplied  by  the  current  gives  the  e.m.f.  in 
phase  with  the  current,  which  is  also  called  the  active  e.m.f. 

A  sine  curve  diagram,  such  as  is  shown  in  Fig. 
356,  serves  very  well  to  enable  the  learner  to  under- 
stand the  relation  between  the  current  and  e.m.fs.  but 
when  this  relation  has  been  fully  mastered,  what  is  known 
as  a  clock  dial  diagram  becomes  more  convenient,  especially 
if  we  desire  to  represent  several  currents  arid  their  e.m.fs.  Fig.  357 
is  virtually  one-half  of  a  clock  dial  diagram.  A  regular  clock 
dial  diagram  to  represent  a  single  alternating  current  is  shown 
in  Figs.  360  to  362.  The  radius  A  represents  the  current,  and  is 


Figs.  360,  361  and  362.    Clock  dial  diagrams. 

supposed  to  rotate  at  a  velocity  equal  to  the  frequency  of  the 
current.  The  strength  of  the  current  for  any  instant  of  time  is 
obtained,  by  measuring  the  distance  from  the  horizontal  line  S  S 
to  the  end  of  the  radius  at  that  particular  instant  as  indicated  by 
line  a  a  in  Fig.  361.  If  A  is  above  the  line  S  S  the  current  is 
positive,  and  if  it  is  below  S  S  the  current  is  negative.  At  the 
instant  when  A  is  in  the  vertical  position,  as  in  Fig.  362,  the 
current  is  at  its  maximum  value,  and  when  A  is  horizontal  as  in 
Fig.  360  the  current  is  zero.  If  we  -desire  to  find  the  relation 
between  the  current  and  impressed  e.m.f.  or  the  self-induction, 
we  draw  radial  lines  of  the  proper  length  to  represent  these 
e.m.fs.  and  in  the  proper  angular  position  with  reference  to  the 
current  and  then  assume  them  to  be  locked  together  when  they 


832 


HANDBOOK    ON    ENGINEERING. 


are  rotating  so  that  the  distances  from  the  ends  of  each  one  to 
the  line  JS  S  at  any  instant  gives  the  values  of  the  quantities  at 
this  instant. 

Diagrams  of  this  type  are  specially  valuable  for  the  represen- 
tation of  polyphase  currents.  Currents  of  this  type  are  commonly 
spoken  of  as  a  two-phase  current,  or  a  three-phase  current,  or  a 
polyphase  current.  Now  there  are  no  multiplephase  currents. 
What  is  improperly  called  a  two-phase  current  is  a  combination 
or  two  simple  alternating  currents  so  timed  that  they  are  out 
of  phase  with  each  other  by  one  quarter  of  a  period,  or  revolu- 
tion. This  constitutes  a  system  of  two-phase  currents.  Three 
simple  alternating  currents  so  timed  as  to  be  out  of  phase  with 
each  other  by  one-third  of  a  period,  constitute  a  system  of  three 
phase  currents.  In  the  first  case  we  have  two  currents,  and  in 
the  second  we  have  three  currents.  These  currents  in  either 
system  are  connected  so  as  to  act  together  in  the  same  system 
of  circuits.  If  the  phase  relations  are  not  such  as  given  above, 
they  cannot  constitute  true,  two  or  three-phase  systems. 


Pigs.  363,  364  and  365.    Phase    relations    for   two-phase    system. 

The  phase  relations  for  the  two-phase  system  are  shown  in  Fig. 
363  and  for  the  three-phase  system  in  Fig.  366.  The  two  currents 
A  B  in  Fig.  363  are  at  right  angles  with  each  other,  and  the  three 
currents  in  Fig.  366  are  120  degrees  apart,  or  one-third  of  a 
period,  or  cycle.  To  obtain  the  values  of  the  two  currents  in 


HANDBOOK    ON    ENGINEERING. 


833 


Fig.  363  at  any  particular  instant,  they  are  rotated  together  as  is  in- 
dicated in  Figs.  364  and  365.  The  values  will  be  equal  to  the  lines 
a  a  and  b  b.  In  the  same  way  the  values  of  the  three  currents  in 
a  three-phase  system  are  obtained  for  any  instant  as  is  illustrated 
in  Figs.  367  and  368. 

For  the  transmission  of  the  currents  of  a  two-phase  system, 
three  or  four  wires  can  be  used.  In  the  three-phase  system,  if 
the  three  currents  are  equal,  three  wires  are  sufficient,  but  if  these 
currents  are  not  equal  a  fourth  wire  is  required  to  carry  the  surplus 


a 


Figs.  366,  367  and   368.    Phase   relations  for  three-phase  system. 

current  as  it  may  be  called.  When  the  three  currents  of  a  three, 
phase  system  are  equal  it  is  called  a  balance  system,  but  if  they 
are  not  equal  the  system  is  unbalanced.  In  Figs.  366  to  368  the 
three  currents  are  drawn  of  equal  length  and  it  will  be  found  that 
in  every  position  in  which  the  lines  can  be  placed  the  sum  of  the 
two  currents  on  one  side  of  line  S  S  will  be  just  equal  to  the  cur- 
rent on  the  other  side,  so  that  if  the  current  is  flowing  away  from 
the  generator  through  one  wire,  it  will  divide  up  and  return 
through  the  other  two,  and  provide  for  each  wire  just  the  amount 
of  current  required.  Thus  in  Fig.  366  the  current  flowing  in  A  is 
zero,  and  the  positive  current  in  B  is  equal  to  the  negative  current 
in  (7.  In  Fig.  367  the  two  positive  currents  a  a  and  b  b  in  lines 
A  J5,  are  just  equal  to  the  one  negative  current  in  (7,  and  this 
is  also  the  case  in  Fig.  368. 


834  HANDBOOK    ON    ENGINEERING. 


HANDBOOK    ON    ENGINEERING.  835 

tive  e.m.f .  in  the  circuit  and  thus  retard  the  current,  so  that  the 
actual  amount  of  current  flowing  will  be  less  than  it  would  be  in 
a  continuous  current  circuit  acted  upon  by  an  impressed  e.m.f.  of 
the  same  magnitude.  As  will  be  noticed,  the  direction  of  the  flux 
at  (7  and  D  is  such  that  they  oppose  each  other,  that  is  the  lines 
C  and  D  flow  through  the  space  between  the  two  sides  of  the  loop 
A  A  in  opposite  directions,  and  on  that  account  the  lines  G  can 
only  extend  to  the  center  of  the  space,  while  lines  D  will  occupy 
the  upper  half.  This  being  the  case  it  is  evident  that  if  the  cir- 
cuit wires  are  brought  closer  together  as  indicated  by  the  lines 
B  JB,  the  magnitude  of  the  magnetic  flux  that  will  surround  each 
wire  will  be  correspondingly  reduced  as  is  indicated  by  the  lines  a  a. 
The  self -inductive  e.m.f.  developed  in  the  circuit  will  be  propor- 
tionaHo  the  magnitude  of  the  flux  that  surrounds  the  wire,  hence 
the  nearer  the  two  sides  are  brought  to  each  other  the  less  the 
self-induction,  and  if  the  two  wires  could  be  placed  side  by  side 
the  inductive  effect  would  be  practically  nothing.  From  this  it 


'£^xD 

•*     <MT 


m 


.  ~-,  -^ 


Fig.  369.     Inductive  action  in  alternating  current  circuits. 

will  be  seen  that  if  an  alternating  current  is  transmitted  to  a  dis- 
tance the  nearer  the  line  wires  to  each  other  the  smaller  the  self- 
induction  developed  in  them. 

In  an  alternating  current  circuit  the  self-induction  developed  in 
every  portion  is  not  the  same,  and  the  total  effect  is  equal  to  the 
sum  of  the  several  effects.  For  example  in  Fig.  370  let  A  A  A 
represent  a  circuit  that  is  fed  by  a  generator  at  G.  The  self- 


836 


HANDBOOK    ON    ENGINEERING. 


induction  on  the  line  A  will  be  small,  specially  if  the  wires 
are  placed  near  each  other.  If  a  number  of  incandes- 
cent lamps  are  connected  at  C  the  self-induction  of  these 
will  be  practically  nothing.  If  at  B  we  place  some  kind  of 
device  that  is  provided  with  wire  in  the  form  of  coils,  then  at  this 
point  a  large  self-induction  will  be  developed,  for  then  the 
magnetic  flux  from  each  turn  of  wire  in  the  coil  will  be  able  to  cut 


Fig.  370.    Illustrating  alternating  current  circuit. 

through  many  other  turns,  and  thus  greatly  increase  the  inductive 
action.  To  determine  the  total  amount  of  inductive  action  in 
this  circuit,  so  as  to  ascertain  the  amount  of  current  that 
will  flow  through  it,  we  will  have  to  find  the  total  impedance 
of  the  circuit,  and  this  we  do  by  finding  the  impedance  of  each 
part  and  then  adding  these  impedances,  but  all  this  operation  is 
carried  out  not  in  the  way  in  which  we  add  figures,  but  in  the 
manner  shown  in  Fig.  359.  The  diagram  Fig.  371  illustrates  the 
operation.  By  actual  measurement  we  can  find  the  resistance  of 
the  line  A  in  ohms  and  we  can  mark  it  down  on  the  diagram  as 
o  a.  By  calculation,  we  find  the  reactance  of  line  A  and  mark  it 
down  as  a  a',  thus  we  obtain  the  impedance  of  oa'  of  the  line. 
Next,  we  find  the  resistance  of  the  lamps  0  which  we  mark  down 
at  a'  &,  and  from  b  draw  b  bf  equal  to  the  reactance  of  the  lamps, 
thus  obtaining  the  impedance  a'  &',  of  the  lamps.  We  now  draw 
b'  c  equal  to  the  resistance  of  B  and  c  c'  equal  to  the  reactance  of 


HANDBOOK   ON   ENGINEERING.  837 

B  and  thereby  obtain  the  impedance  b'  c'  of  B.     We  now  join  o 


Fig.  371.     Determining  total  inductive  action. 

with  c'  and  obtain  the  line  G  which  is  the  total  impedance  of  the 
circuit,  and  line  B,  which  is  the  total  reactance,  while  line  A  is 
the  total  resistance.  A  glance  at  the  diagram  will  show  that  the 
total  impedance  C  is  less  than  the  sum  o  a'  a'  b'  and  b'  c'  if  these 
were  added  in  the  ordinary  way,  so  that  the  total  impedance  of  a 
circuit  can  be  less  than  the  direct  sum  of  the  impedances  of  its 
several  parts. 


Fig.  872.    Showing  e.m.f.  and  current  in  phase. 

The  angle  of  lag  between  the  current  and  impressed  e.m.f. 
in  an  alternating  circuit  plays  a  very  important  part  in  determin- 
ing the  actual  amount  of  energy  that  is  transmitted.  In  a 
continuous  current  circuit  the  energy  is  always  equal  to  the 


838 


HANDBOOK    ON    ENGINEERING. 


product  of  the  volts  by  the  amperes  but  in  an  alternating  circuit 
it  may  be  equal  to  this  product  and  it  may  not  be  as  much 
as  one  per  cent  of  this  product.  What  proportion  of  the  product 
of  the  volts  by  the  amperes  will  represent  the  actual  energy  trans- 
mitted will  depend  upon  the  angle  of  lag  between  the  current 
and  the  impressed  e.m,f.,  the  greater  this  angle  the  less  the  en- 
ergy. The  way  in  which  the  angle  of  lag  affects  the  amount  of 
energy  flowing  in  the  circuit  can  be  made  clear  by  means  of  Figs. 
372  to  374.  In  these  figures,  curve  A  represents  the  impressed 
e.m.f.  and  curve  B  is  the  current,  while  the  shaded  curves  repre- 
sent the  energy.  In  Fig.  372  the  impressed  e.m.f.  and  the  current 


Fig.  373.    Angle  of  lag  affects  energy  in  circuit. 

are  shown  in  phase  with  each  other,  and  as  a  result  the  curves  (7, 
which  represent  the  energy  are  drawn  above  line  0  T,  thus  show- 
ing that  all  the  energy  is  positive,  and  it  is  equal  to  the  direct 
product  of  the  volts  by  the  amperes.  In  Fig.  373  the  current  and 
impressed  e.m.f.  are  drawn  out  of  phase  90  degrees.  Starting 
from  0,  the  e.m.f.  is  positive  while  the  current  is  negative,  curve 
B  being  below  line  0  T.  This  means  that  the  current  and  e.m.f. 
act  against  each  other  hence  the  energy  represented  is  negative. 
After  the  first  quarter  of  a  period,  the  current  becomes  positive 


HANDBOOK    ON    ENGINEERING. 


839 


and  then  the  energy  is  positive.  Thus  for  the  first  half  period  we 
have  two  energy  curves,  D  negative,  and  C  positive,  both  of  these 
are  equal  and,  therefore,  just  offset  each  other,  so  that  the  net 
energy  flowing  in  the  circuit  during  this  time  is  zero.  As  will  be 
seen,  during  the  following  half  periods,  the  same  operation  is  re- 
peated, so  that  the  actual  result  is  that  energy  is  put  into  the  circuit 
during  one  quarter  period,  and  during  the  next  quarter  it  is  taken 


Fig.  374.    Energy  in  circuit  affected  by  lag. 

out,  and  the  actual  energy  flowing  through  the  circuit  is  nothing. 
The  action  is  the  same  as  when  a  swing  is  set  in  motion,  during 
the  first  half  of  each  swing  energy  is  .accumulated  by  the  descent 
of  the  weight,  but  during  the  next  half  it  is  all  absorbed  in  lifting 
the  same  weight,  and  unless  we  supply  from  outside  enough  en- 
ergy to  overcome  the  friction  the  swing  will  soon  come  to  a 
standstill.  In  an  alternating  current  circuit,  if  the  impressed 
e.m.f.  and  the  current  were  out  of  phase  90  degrees  no  energy 
would  be  introduced  into  the  circuit,  hence,  no  current  at  all 
could  flow,  but  if  the  angle  is  a  trifle  less  than  90,  say  89,  a  suf- 
ficient amount  of  energy  can  be  put  into  the  circuit  to  overcome 
the  resistance  loss,  and  then  a  strong  current  will  sway  back  and 
forth  that  is  not  capable  of  doing  any  work.  A  current  of  this 


840  HANDBOOK   ON   ENGINEERING. 

• 

kind  is  called  a  wattless  current  as  it  carries  no  energy.  The  rea- 
son why  it  carries  no  energy  is  that  the  self-induction  very  nearly 
balances  the  impressed  e.m.f.  so  that  the  effective  e.m.f .  is  very 
small,  in  fact  it  is  just  enough  to  force  the  current  against  the 
resistance  of  the  circuit. 

In  Fig*  374  the  current  and  impressed  e.m.f.  are  shown  out  of 
phase  by  an  angle  of  45  degrees,  and  as  will  be  seen  the  shaded 
curves  C  which  represent  positive  energy,  are  much  larger  than 
those  below  line  0  T,  which  represent  negative  energy.  The 
difference  between  these  two  is  the  actual  energy  flowing  in  the 
circuit.  It  can  be  clearly  seen  that  the  smaller  the  angle  of  lag 
between  the  current  and  impressed  e.m.f.  the  larger  the  shaded 
curves  above  line  0  T  and  the  smaller  those  below  the  line ; 
hence,  the  greater  the  energy  flowing  in  the  circuit. 

By  the  use  of  condensers,  the  effect  of  self-induction  can  be 
counteracted,  and  in  that  way  the  lag  of  the  current  can  be  re- 
duced and  thus  the  energy  in  the  circuit  can  be  increased.  A 
condenser  is  a  device  that  is  so  constructed  as  to  be  able  to  re- 
ceive a  very  large  electriostatic  charge.  To  explain  the  nature 
of  electrostatic  charges  so  that  they  may  be  understood  we  may 
say  that  bodies  arranged  so  as  to  hold  a  charge  will  carry  this 
charge  upon  their  surface.  Thus  we  can  picture  to  the  mind's 
eye  the  charge  as  flowing  over  the  surface  until  it  completely 
covers  it.  When  a  condenser  is  used  in  an  alternating  current 
circuit,  it  is  charged  and  discharged  each  time  the  current 
alternates,  and  the  time  relation  of  the  charging  and  discharging 
currents  is  such  as  to  be  directly  opposite  to  the  current  that  would 
flow  under  the  effect  of  the  self-induction,  or,  to  put  it  in  another 
way,  the  e.m.f  of  the  condenser  current  is  180  degrees  out  of 
phase  with  the  self-induction.  Now,  by  properly  proportioning 
the  condenser  it  can  be  made  to  just  balance  the  self-induction, 
and  then  we  get  the  relations  illustrated  in  Fig.  3  75  in  which  curve  B 
represents  the  self -induction,  curve  C  the  condenser  e.m.f.  which 


HANDBOOK    OK    ENGINEERING. 


841 


is  directly  opposite  and  of  equal  magnitude.  Curve  A  represents 
the  impressed  e.m.f .  as  well  as  the  current,  both  being  in  phase 
with  each  other. 

The  general  principle  of  construction  of  a  condenser  is  illus- 
trated in  Fig.  376,  in  which  the  plates  A  B  represent  the  condenser, 


Fig.  375.    Self-induction  and  condenser  e.m.f. 

and  G  the  generator  that  provides  the  current,  the   connecting 
wires  being  S  S.     A  device  of  this  kind,  if  placed  in  a  continuous 

8 


B 


Fig.  876.    Principle  of  the  condenser. 

current  circuit,  will  simply  prevent  the  flow  of  current ;  but  when 
connected  in  an  alternating  current  circuit,  if  of  the  proper  pro- 
portions, will  act  as  if  it  did  not  break  the  circuit.  This  is  because 


842 


HANDBOOK   OK   ENGINEERING. 


the  large  surfaces  on  the  plates  A  B  act  as  reservoirs  and  accumu- 
late all  the  current  that  flows  into  them  during  the  short  time  each 
impulse  lasts.  When  the  current  reverses,  the  charge  in  the  con- 
denser runs  out  together  with  the  generator  current.  We 
can  thus  consider  that  if  a  positive  impulse  of  the  current  fills 
plate  A  and  empties  plate  B,  a  negative  impulse  will  reverse  the 
operation. 

Mutual  induction*  —  In  connection  with  Fig.  351  it  was  shown 
that  when  an  alternating  current  flows  through  a  wire,  the  alter- 


Fig.  377.    Illustrating  mutual  induction. 

nating  magnetic  flux  that  surrounds  the  wire,  if  it  cuts  through 
any  other  wires  running  parallel  with  it  will  induce  e.m.fs.  in 
them.  The  direction  and  phase  of  these  e.m.fs.  will  be  the  same 
as  that  of  the  self-induction  in  the  wire  carrying  the  current.  If 
we  have  two  wires  running  parallel  with  each  other  and  alternat- 
ing currents  flow  through,  then  the  action  of  wire  No.  1  upon 
wire  No.  2  will  be  the  same  as  that  of  No.  2  upon  No.  1.  This 
action  is  called  mutual  induction,  and  it  is  made  use  of  in  the 


HANDBOOK    ON    ENGINEERING. 


843 


construction  of  an  apparatus   used  for  transforming  alternating 
currents  which  is  commonly  called  a  transformer. 

By  the  aid  of  Fig.  377  the  principles  of  mutual  induction  can  be 
made  quite  clear.  In  this  diagram  suppose  that  the  circle  A  rep- 
resents one  wire  through  which  an  alternating  current  is  flowing, 
and  circle  B  represents  another  wire  carrying  an  alternating  cur- 
rent. If  these  two  wires  are  some  distance  apart,  it  is  clear  that 
a  considerable  portion  of  the  magnetic  flux  of  A  will  not  cut 
through  5,  and  in  like  manner  that  a  considerable  portion  of 
the  flux  of  B  will  not  cut  though  A,  as  is  indicated  by 


Fig.  378.    Inductive  effect  of  wires  upon  each  other. 

the  dotted  circles  at  a  a  a.  In  any  case,  however,  some 
of  the  flux  of  one  wire  will  cut  through  the  other.  From 
this  it  follows  that  the  effect  of  the  current  in  each  wire 
upon  the  other  wire  will  be  less  than  that  upon  itself, 
but  the  closer  the  wires  are  to  each  other  the  nearer  equal 
the  effects  will  be.  When  it  is  desired  to  avoid  the  effects  of 
mutual  induction  as  far  as  possible  the  wires  must  be  separated 
to  the  greatest  distance,  and  when  we  desire  to  make  the  mutual 
inductive  effect  the  greatest,  we  must  bring  the  wires  as  close 


844  HANDBOOK    ON    ENGINEERING. 

together  as  possible.  The  inductive  effect  of  wires  upon  each 
other  in  some  cases  produces  very  objectionable  results,  for 
example  when  telephone  wires  are  run  side  by  side  for  any 
distance  the  inductive  action  of  one  wire  upon  the  other  serves 
to  render  the  conversation  indistinct.  Why  this  is  so  it  can  be 
appreciated  at  once  from  an  inspection  of  Fig.  378,  which  shows 
a  pole  carrying  four  wires.  Telephone  currents  are  not  alter- 
nating but  they  pulsate  and  thus  produce  the  same  effect  as  if 
they  were  alternating.  In  Fig.  378  the  circles  drawn  around 
each  one  of  the  wires  as  will  be  seen  cut  through  all  the  other 
wires.  If  the  two  upper  wires  belong  to  one  circuit  and  the  two 
lower  ones  to  another,  then  if  one  set  of  wires  are  crossed  at  every 
three  or  four  poles  so  that  the  wire  running  on  the  right  side 
for  a  certain  distance  will  then  be  changed  over  to  the  left  side, 
the  inductive  actions  will  be  counteracted  to  a  very  great  extent 
and  this  method  is  followed  in  stringing  telephone  wires.  It  is 
also  used  in  regular  alternating  current  circuits  when  interference 
between  different  circuits  is  to  be  avoided. 

With  regards  to  the  two  wires  belonging  to  the  same 
circuit,  it  is  advantageous  to  string  them  as  close  together  as 
possible,  for  in  this  case,  the  effect  of  mutual  induction  is  to 
neutralize  the  effect  of  self-induction.  Referring  to  Fig.  369  it 
can  be  seen  at  once  that  if  the  magnetic  flux  at  0  develops  a  self- 
induction  in  lower  A  toward  the  right,  it  will  develop  an  induc- 
tion in  upper  A  also  towards  the  right,  but  with  reference  to  the 
wire  itself  this  induction  will  be  just  opposite  to  that  in  the  lower 
side  so  that  the  two  will  counteract  each  other.  Thus  to  reduce 
the  reactance  of  the  line,  the  two  sides  of  the  circuit  must  be 
placed  as  near  together  as  is  practicable. 

Transformers*  —  A  transformer  is  an  apparatus  in  which  the 
principle  of  mutual  induction  is  utilized  for  the  purpose  of  gener- 
ating a  second  current  by  the  inductive  action  of  a  primary 
current.  Referring  to  Fig.  377  it  can  be  seen  that  if  wire  B  is 


HANDBOOK    ON    ENGINEERING. 


845 


closed  upon  itself  the  e.m.f.  induced  in  it  by  the  magnetic  flux 
issuing  from  A  will  cause  a  current  to  flow  and  then  this  current, 
which  is  brought  into  existence  by  the  inductive  action  of  the 
current  in  A,  will  in  turn  develop  a  magnetic  flux  that  will  react 
upon  wire  A  in  precisely  the  same  manner  as  if  the  current  were 
not  induced  in  J5,  but  it  came  from  an  independent  source.  In  a 
transformer,  the  wire  is  wound  in  the  form  of  compact  coils,  and 
one  of  these  coils,  which  is  called  the  primary,  is  connected  with 
an  alternating  current  circuit.  The  current  flowing  through  this 
coil  induces  a  current  in  the  other  coil  which  is  called  the  second- 
ary. The  general  construction  of  a  transformer  can  be  under- 


,''~~f~l-  ^a 

f  I     s^~  -  -Uu         V      \ 

I    '      r^       N.  .  \ 


-H- 


m 


Fig.  370.    Priiiciple  of  the  transformer. 

stood  from  Fig.  379.  An  iron  core  G  is  provided  upon  which  are 
wound  two  coils  marked  A  and  B.  The  coil  A  which  is  the  prim- 
ary, is  connected  with  an  alternating  current  circuit,  and  thus  the 
iron  coreO  is  strongly  magnetized.  The  presence  of  the  iron  core 
G  serves  to  greatly  increase  the  magnetic  flux  but  does  not  in  any 
way  interfere  with  its  alternating  properties,  so  that  it  increases 
and  decreases  and  changes  its  direction  in  precisely  the  same 
manner  as  the  flux  that  surrounds  a  single  wire.  The  flux  de- 


846  HANDBOOK    ON   ENGINEERING. 

veloped  by  A,  swells  out  as  indicated  by  the  lines  a  a  a  and  cuts 
through  the  side  of  the  secondary  coil  B.  If  the  circuit  through 
this  coil  is  close  an  alternating  current  will  be  generated  in  it, 
and  this  current  will  develop  a  magnetic  flux  that  will  swell  out 
and  cut  the  side  of  the  primary  coil  A.  The  e.m.f.  induced  in 
A  by  the  flux  of  B  will  be  in  opposition  to  the  self-induction  de- 
veloped by  its  own  flux,  hence,  if  the  circuit  through  B  is  open, 
the  current  flowing  through  A  will  be  small  because  the  self- 
induction  will  counteract  the  impressed  e  m.f .  so  as  to  leave  but 
a  small  effective  e.m.f.  As  soon  as  the  circuit  through  B  is 
closed,  the  inductive  action  of  this  coil  upon  A  will  offset  to  a 
certain  extent  the  self-induction  and  thus  assist  the  impressed 
e.m.f.  in  forcing  more  current  through  A.  The  more  the  current 
through  B  is  increased,  the  stronger  its  action  upon  A  and  as  a 
result  the  more  the  self-induction  of  A  will  be  neutralized  and  the 
stronger  the  primary  current  will  become.  This  action,  which 
occurs  in  a  perfectly  natural  manner,  serves  to  make  the  trans- 
former a  self -regulating  apparatus,  so  that  if  a  strong  current  is 
required  in  the  secondary  circuit,  a  strong  current  passes  through 
the  primary  so  as  to  furnish  the  energy  necessary  to  develop  the 
strong  secondary  current.  If  no  current  is  drawn  from  the 
secondary,  the  primary  current  is  reduced  to  nearly  nothing. 

To  explain  fully  the  action  in  a  transformer  would  require  a 
rather  lengthy  discussion  of  the  principles  involved,  but  the 
action,  in  a  general  way,  can  be  made  clear  without  going  deeply 
into  the  theory.  In  explaining  the  phase  relation  of  the  current, 
the  self-induction  and  the  impressed  e.mafs.  in  connection  with 
Fig.  357  it  was  shown  that  theangle  between  the  self-induction  and 
the  current  is  90  degrees,  and  that  the  angle  between  the  current 
and  the  impressed  e.m.f.  can  be  anything  from  zero  up  to  nearly 
90  degrees.  If  the  current  is  passed  through  transformers  or 
other  inductive  devices,  the  current  will  lag  considerably. 
Suppose  it  lags  10  degrees,  then  the  total  angle  between  the  im- 


HANDBOOK  ON  'ENGINEERING.  847 

pressed  e.m.f.  and  the  self-induction  will  be  100  degrees.  Now 
in  a  transformer  the  e.m.f.  induced  in  the  secondary  coil  is  in 
phase  with  the  self-induction  in  the  primary  coil,  hence,  with  the 
above  angles  it  would  be  100  degrees  behind  the  impressed  e.m.f. 
in  the  primary  coil.  Now  if  the  secondary  current  lags  as  much 
as  the  primary,  it  will  be  110  degrees  behind  the  primary  im- 
pressed e.m.f.  and  the  magnetic  flux  developed  by  this  current 
will  induce  an  e.m.f.  in  the  primary  coil  90  degrees  behind 
itself  or  200  degrees  behind  f_ie  primary  impressed  e.m.f. 
This  e.m.f.  induced  in  the  primary  coil  by  the  action  of  the  sec- 
ondary current  not  only  counteracts  the  self-induction  in  the 
primary  coil,  but  in  addition  changes  the  phase  relation  between 
the  primary  current  and  its  impressed  e.m.f.,  making  the  angle 
smaller.  This  change  in  the  phase  relation  between  the  current 
and  impressed  e.m.f.  results,  in  turn,  in  a  change  of  the  phase 
relation  of  the  secondary  current,  and  this  change  in  the  phase  of 
the  secondary  makes  a  corresponding  change  in  the  phase  of  the 
primary.  If  we  were  to  trace  up  the  action  back  and  forth  from 
primary  to  secondary  currents  we  would  finally  arrive  at 
the  true  phase  relation  of  the  currents  and  e.m.fs.  in  both  circuits 
but  this  is  a  complicated  and  unnecessary  process  of  reasoning. 
We  can  easily  see  that  the  current  induced  in  the  secondary  coil 
will  have  a  certain  phase  relation  with  respect  to  the  primary 
current,  and  we  can  further  see  that  the  combined  magnetizing 
effect  of  the  two  currents,  the  primary  and  secondary,  is  the 
same  as  that  of  a  single  current  having  a  phase  intermediate 
between  the  phases  of  these  two.  Following  this  course  of 
reasoning  we  have  only  one  inductive  action  to  deal  with  and  this 
is  in  such  a  phase  relation  that  as  it  increases  it  decreases  the  self- 
inductive  e.m.f.  in  the  primary  and  thus  permits  more  current  to 
pass  through  this  coil,  and  this  increase  in  current  in  the  primary 
causes  a  corresponding  increase  in  the  secondary  current.  When 
the  secondary  current  is  very  small  the  self-induction  in  the 


848  HANDBOOK    ON    ENGINEERING. 

primary  is  very  great  and  as  a  result  the  lag  of  the  primary 
current  is  increased  and  its  strength  is  decreased.  As  the  sec- 
ondary current  increases,  the  self-induction  in  the  primary 
decreases,  and  the  lag  of  the  primary  current  reduces  while 
the  current  strength  increases.  The  strength  of  the  secondary 
current  is  varied  by  varying  the  resistance  in  the  secondary 
circuit ;  if  this  resistance  is  reduced  the  current  is  increased. 

To  make  a  transformer  as  perfect  as  possible  it  is  necessary  to 
place  the  primary  and  secondary  coils  in  such  a  position  that 
the  mutual  induction  between  them  may  be  the  greatest  pos- 
sible, that  is  so  that  all  the  magnetic  flux  developed  by 
the  primary  coil  may  cut  through  the  secondary  and  all 
the  flux  of  the  secondary  may  cut  through  the  primary. 
If  the  coils,  are  arranged  as  in  Fig.  379  it  can  be  seen  at  once  that 
all  the  flux  of  A  will  not  cut  through  B  and  in  like  manner  all  the 
flux  of  B  will  not  cut  through  A.  It  is  not  possible  to  arrange 
the  coils  so  that  all  the  flux  of  one  coil  will  pass  through  all  the 
turns  of  wire  on  the  other  coil,  but  this  condition  can  be  very 
nearly  realized.  If  one-half  of  coil  A  is  wound  on  each  side  of 
the  core  G  and  then  the  B  coil  is  wound  in  two  parts  directly 
over  the  A  coils  the  chance  for  the  flux  of  one  coil  to  not  pass 
through  the  other  coil  will  be  greatly  reduced. 

The  flux  that  does  not  pass  through  the  opposite  coil  is  called  a 
leakage  flux,  thus  in  Fig.  379  the  lines  a  that  pass  through  coil 
A  but  not  through  B  constitute  the  leakage  from  coil  A  and  in 
like  manner  the  flux  oH  coil  B  that  does  not  pass  through  A  is 
the  leakage  of  B.  The  leakage  flux  represents  just  so  much  mag- 
netism thrown  away,  hence  the  effort  of  the  designer  is  to  arrange 
the  coils  so  as  to  reduce  it  to  the  smallest  amount  possible.  If 
the  two  coils  were  wound  together,  that  is,  if  we  took  the  wires 
and  wound  them  side  by  side  forming  a  single  coil,  the  leakage 
would  be  practically  nothing,  but  this  construction  cannot  be  used 
as  with  it  there  would  be  great  danger  of  the  insulation  between 


HANDBOOK   ON   ENGINEERING. 


849 


the  coils  giving  away,  and  this  would  destroy  the  transformer. 
This  form  of  winding  can  be  approximated  to  by  winding  each 
coil  in  many  sections  and  placing  these  in  sandwich  fashion  upon 


Fig.  380.    Position  of  transformer  coils  on  iron  core. 

the  iron  core  as  is  shown  in  Fig.  380  in  which  the  sections  forming 
one  coil  are  shaded,  and  those  of  the  other  coil  are  not.  This  is 
the  construction  that  is  followed  generally  in  large  transformers. 
In  the  majority  of  designs,  however,  the  primary  and  secondary 
coils  are  wound  one  over  the  other. 

Transformers  are  used  for  the  purpose  of  changing  the  voltage 
of  the  current.  The  name  transformer  is  misleading,  as  it  creates 
the  impression  that  the  device  transforms  the  current,  when  as 
shown  in  the  foregoing  it  does  nothing  of  the  kind,  it  simply 
generates  a  secondary  current,  which  is  in  no  way  connected  with 
the  primary.  When  electric  energy  is  transmitted  to  a  consider- 
able distance  by  means  of  alternating  currents,  the  voltage  used 
is  much  higher  than  is  required  for  the  operation  of  lamps 
or  motors,  hence,  at  the  receiving  end  of  the  line  this  cur- 
rent is  passed  through  transformers  and  secondary  currents  are 
generated  in  these  that  are  of  the  voltage  desired.  The  voltage 


850  HANDBOOK   ON    ENGINEERING. 

of  the  secondary  current  is  controlled  by  the  number  of  turns  of 
wire  placed  upon  the  secondary  coils.  Roughly  speaking,  if 
the  primary  coil  has  ten  times  as  many  turns  as  the  secondary 
the  voltage  of  the  secondary  current  will  be  one-tenth  of  that  of 
the  primary.  If  the  primary  voltage  is  2000  and  the  secondary 
is  100  the  primary  coil  will  have  twenty  times  as  many  turns  of 
wire  as  the  secondary. 

Transformers  that  deliver  a  secondary  current  of  lower  volt- 
age than  the  primary  are  called  lowering  transformers,  while 
those  that  deliver  a  secondary  of  higher  voltage  are  called  raising 
transformers.  For  distributing  current  to  consumers,  lowering 
transformers  are  used.  But  in  long  distance  transmission  plants, 
where  the  current  in  the  transmission  line  has  ane.m.f.  of  any- 
where from  10,000  to  30,000  volts,  raising  transformers  are 
used  at  the  power  house,  and  these  take  the  current  from  the 
generators,  which  may  be  of  1,000  or  2,000  volts  and  deliver  to 
the  line  a  secondary  current  of  10,000  or  more  volts. 

Transformers  cannot  be  used  with  continuous  currents  for  the 
simple  reason  that  as  these  currents  do  not  fluctuate  the  magnetic 
flux  developed  by  them  remains  stationary  and,  therefore,  there 
is  no  inductive  action. 

A  medium  size  transformer  is  shown  in  Fig.  381.  The  com- 
plete transformer  is  seen  at  the  right  side  of  the  illustration.  In 
the  center  is  shown  the  lower  part  of  the  iron  core,  with  the  wire 
removed  from  one  leg,  this  wire  being  shown  on  the  left.  The 
iron  plates  at  the  bottom  of  the  figure  form  the  upper  part  of  the 
iron  core. 

The  iron  core  of  a  transformer  is  built  up  out  of  sheet  iron. 
It  could  not  be  made  a  solid  mass,  for,  if  it  were,  secondary  cur- 
rents would  be  induced  in  it,  and  thus  the  energy  in  the  primary 
current  would  be  used  up  in  developing  useless  currents  in  the  iron 
core.  The  sheet  iron  laminations  are  insulated  from  each  other, 
so  as  to  prevent  the  development  of  currents  in  the  core. 


HANDBOOK    ON    ENGINEERING. 


851 


As  can  be  seen  from  the  illustration,  the  wire  wound  on  each 
leg  of  the  core  belongs  in  part  to  the  primary  and  in  part  to  the 
secondary  circuit.  If  the  primary  wire  is  proportioned  so  that  it 
is  proper  for  a  1,000-volt  current  when  the  parts  on  the  two  legs 
are  connected  in  series,  then  it  can  be  made  proper  for  500  volts 


j 


Fig.  381.    Showing  outer  coyering  of  transformer. 

by  connecting  the  two  parts  in  parallel.  If  the  secondary  coils 
will  develop  a  voltage  of  100  when  both  parts  are  connected  in 
series,  they  will  develop  50  volts  if  both  parts  are  connected  in 
parallel,  but  in  this  case  the  current  will  be  doubled. 

The  transformer  as  shown  to  the  right  in  Fig.  381,  is  complete, 
but  for  the  purpose  of  protecting  the  wire  an  outer  casing  is  pro- 


852  HANDBOOK   ON   ENGINEERING. 

vided.  For  high  voltage  transformers,  this  casing  is  made  water 
tight  and  is  filled  with  oil  so  as  to  improve  the  insulation  of  the 
apparatus.  Very  large  transformers  are  provided  with  means  for 
cooling  them.  In  some,  air  is  forced  through  the  coils  and  iron 
core.  In  others,  coils  of  pipe  are  placed  within  the  casing  and 
water  circulates  through  these. 

Alternating  current  generators.  In  alternating  current  gen- 
erators the  field  is  magnetized  permanently  by  means  of  a  con- 
tinuous current.  This  current  is  obtained,  generally,  from  a  small 
continuous  current  generator  that  is  called  an  exciter.  Some  alter- 
nators, as  a  rule  of  small  capacity,  are  provided  with  a  commu- 
tator to  rectify  a  portion  of  the  current  the  machine  generates  so 
as  to  provide  a  continuous  current  to  magnetize  the  field.  An 
alternating  current  cannot  be  used  to  magnetize  the  field  because 
the  field  magnetism  must  remain  unchanged. 

Alternators  are  also  arranged  so  that  the  field  is  magnetized 
by  the  combined  action  of  the  two  continuous  currents  above 
mentioned,  that  is,  by  the  current  from  a  separate  exciter  and 
the  current  derived  from  the  armature.  Alternators  excited  in 
this  manner  are  called  compound  machines  and  are  the  counter- 
part of  the  continuous  current  generator.  Alternators  that  are 
excited  by  the  current  from  a  separate  exciter  alone  are  the  coun- 
terpart of  the  plain  shunt  wound  continuous  current  generator. 

There  are  several  other  ways  in  which  the  field  can  be  magnet- 
ized to  make  an  alternator  of  the  compound  type,  and  the  most 
important  of  these  will  be  found  fully  explained  under  the  head- 
ing of  "Compensated  Generators." 

The  object  of  compound  winding  in  alternators  is  the  same  as 
In  continuous  current  generators,  that  is,  to  keep  the  voltage  con- 
stant and  not  allow  it  to  drop  as  the  current  strength  increases. 
Large  alternators  used  in  central  stations  are  always  of  the  com- 
pound type. 

The  way  in  which  alternating  current  generators  act  can  be 


HANDBOOK  ON   ENGINEERING. 


853 


understood  from  the  diagrams  Figs.  382  to  386.  In  Fig.  382  P 
and  N  represent  the  poles  of  the  field  magnet  of  a  two-pole 
machine.  The  armature  is  provided  •  with  a  single  coil  of  wire 
marked  a.  When  this  coil  is  in  the  position  shown,  no  e.m.f. 
will  be  induced  in  it,  but  as  it  begins  to  rotate  from  this  position 
an  e.m.f.  will  begin  to  be  induced,  and  this  will  increase  in  mag- 
nitude until  one -quarter  of  a  revolution  has  been  made,  when  it 
will  be  at  the  maximum  value.  During  the  next  quarter  revolu- 
tion the  e.m.f.  will  gradually  reduce,  becoming  zero  when  the 
half  turn  is  completed.  During  the  next  half  turn  the  e.m.f.  will 
again  rise  to  a  maximum  and  fall  to  zero,  but  it  will  be  oppositely 


Figs.  382,  383  and  384.    Generating  current  in  alternator. 

directed,  so  that  if  during  the  first  half  turn  the  e.m.f.  is  posi- 
tive, during  the  next  half  it  will  be  negative,  and  this  operation 
will  be  repeated  for  each  revolution  of  the  armature.  Thus  it 
will  be  seen  that  if  the  armature  revolves  ten  times  in  a  second, 
the  frequency  of  the  current  generated  will  be  ten,  and  in  any 
case  the  frequency  will  be  equal  to  the  number  of  revolutions  the 
armature  makes  in  a  second.  This  is  true  for  a  two-pole  machine, 
if  the  generator  has  four  poles  the  frequency  of  the  current  will 
be  equal  to  twice  the  number  of  revolutions  per  second  and  for 
any  greater  number  of  poles  the  frequency  will  be  equal  to  the 
number  of  revolutions  of  the  armature  per  second  multiplied  by 
half  the  number  of  poles.  Alternating  current  generators  are 
always  made  with  a  large  number  of  poles  so  that  the  frequency 
required  may  be  obtained  without  running  the  armature  at  too 
great  a  speed. 


854  HANDBOOK    ON    ENGINEEKING. 

The  diagram  Fig.  382  illustrates  a  simple  alternating  current 
generator,  or  what  is  called  a  single-phase  generator.  A  single- 
phase  machine  is  one  that  has  one  coil  on  the  armature  for  each 
pair  of  poles  in  the  fields  and  generates  one  alternating  current. 

Fig.  383  illustrates  diagrammatically  a  two-phase  generator.  A 
two-phase  generator  is  an  alternating  current  generator  that  gene- 
rates two  alternating  currents  that  are  out  of  phase  with  each 
other  by  one-quarter  of  a  period,  that  is,  by  90  degrees.  Such  a 
generator  is  provided  with  two  coils  or  sets  of  coils  for  each  pair 
of  poles  and  these  are  placed  at  right  angles  to  each  other  in  a 
two-pole  machine,  and  so  that  the  sides  of  one  set  come  opposite 
the  centers  of  the  other  set,  in  multipolar  machines. 

In  Fig.  383  it  will  be  seen  that  coil  a  is  in  the  same  position  as 
the  coil  in  Fig.  382,  hence  no  e.m.f.  is  being  induced  in  it.  Coil 
&,  however,  is  in  the  position  in  which  the  induced  e.m.f.  is  of  the 
maximum  value,  thus  it  will  be  seen  that  as  the  armature  revolves 
the  e.m.f.  in  one  coil  will  rise  toward  the  maximum  while  that  in 
the  other  coil  will  be  decreasing  toward  zero. 

Fig.  384  illustrates  a  three-phase  generator.  A  three-phase 
generator  is  a  machine  that  generates  three  alternating  currents 
that  are  out  of  phase  with  each  other  by  an  angle  of  120  der 
grees,  or  one-third  of  a  period.  Such  a  machine  has  three  coils 
or  sets  of  coils  for  each  pair  of  field  poles. 

In  Fig.  384  it  will  be  seen  that  coil  a  is  in  the  position  in  which 
no  e.m.f.  is  generated,  and  if  we  assume  that  the  armature  is  re- 
volving in  the  direction  of  the  hands  of  a  clock,  then  the 
e.m.f.  induced  in  coil  b  is  very  near  the  maximum  value,  but  is 
still  increasing,  and  will  become  the  maximum  when  the  coil 
reaches  the  horizontal  position.  In  coil  c  the  e.m.f.  has  passed 
the  maximum  and  is  reducing  toward  zero,  which  value  it  will 
reach  when  the  coil  reaches  the  vertical  position,  or  the  position 
in  which  a  now  is. 

If  an  alternator  is  of  the  multipolar  type  the  coils  will  be  dis- 


HANDBOOK    ON    ENGINEERING. 


855 


posed  in  the  manner  shown  in  Fig.  385.  If  it  is  a  single-phase 
machine  it  will  have  one  set  of  coils  only,  those  marked  A.  If  it 
is  a  two-phase  generator  it  will  have  two  sets  of  coils,  the  addi- 


Fig.  385.    Arrangement  of  coils  in  multipolar  alternator. 

tional  set  being  placed  in  the  position  shown  in  broken  lines  and 
marked  B.  In  this  construction  the  machine  appears  to  have  as 
many  A  coils  as  there  are  poles  and  the  same  number  of  B  coils, 
which  is  in  contradiction  to  the  statement  made  above  that  a  single- 
phase  machine  has  one  coil  for  each  pair  of  poles.  The  truth, 


Fig.  386.    Arrangement  of  coils  in  three-phase  generator. 

however,  is  that  each  coil  in  Fig.  385  is  virtually  one-half  of  a 
coil.  Fig.  386  shows  the  way  in  which  the  coils  are  arranged  in  a 
three-phase  generator  of  the  multipolar  type,  the  three  sets  of 
coils  being  marked  ABC.  In  monocyclic  generators  the  coils 


856 


HANDBOOK    ON    ENGINEERING. 


are  arranged  as  in  Fig.  385,  but  they  differ  from  the  two-phase 
winding  in  that  the  B  coils  are  one-quarter  the  size  of  the  A  coils. 
In  actual  generators  the  armature  coils  are  seldom  given  the  form 
shown  in  these  diagrams,  but  whatever  the  form  may  be  the  prin- 
ciple of  winding  is  the  same. 

In  an  alternator  the  armature  coils  forming  one  set  are  connected 
in  series  with  each  other,  and  the  entering  end  of  the  first  coil  and 
the  leaving  end  of  the  last  coil  are  connected  with  collector  rings 
mounted  upon  the  armature  shaft,  and  the  current  is  taken  from 
these  by  means  of  brushes  similar  to  the  commutator  brushes  of 


Fig.  387.    Revolving  field  alternator. 

continuous  current  machines.  In  monocyclic  generators  one  end 
of  the  B  set  of  coils  is  connected  with  the  middle  point  of  the 
A  set,  and  the  three  remaining  ends  are  connected  with  col- 
lector rings.  This  is  the  arrangement  with  generators  of 
what  is  known  as  the  revolving  armature  type,  which  is  the 


HANDBOOK    ON   ENGINEERING.  857 

one  illustrated  in  Fig.  382  to  386.  There  is  another  type  in 
which  the  outer  part,  which  is  stationary,  is  the  armature,  and  the 
revolving  part  is  the  field.  Machines  of  this  kind  are  called  re- 
volving field  alternators.  The  principle  of  operation  is  the  same 
in  both  types,  but  the  revolving  field  type  has  the  ad  vantage  that, 
as  the  armature  is  stationary,  no  collector  rings  and  brushes  are 
required  to  take  off  the  current.  All  that  is  necessary  is  to  pro- 
vide binding  posts  to  which  the  ends  of  the  armature  coils  are  con- 
nected, and  from  these  the  external  circuit  wires  are  run  off. 

A  revolving  field  alternator  is  shown  in  Fig.  387.  In  machines 
of  this  type,  the  field  magnetizing  coils  are  mounted  on  the 
periphery  of  the  revolving  part,  hence  the  current  that  traverses 
them  must  pass  through  collector  rings  mounted  upon  the  shaft. 
These  rings  are  clearly  shown  in  the  illustration,  the  collector 
brushes  being  held,  insulated  from  each  other,  by  the  stand 
located  in  front  of  the  rings.  Thus  it  will  be  seen  that  this  type 
of  machine  requires  collector  rings,  just  the  same  as  the  revolving 
armature  type,  but  the  difference  between  the  two  is  that  in  the 
latter  the  whole  armature  current  passes  through  the  collector 
rings,  and  on  that  account  they  must  be  made  very  large,  while 
in  the  revolving  field  machines  they  can  be  made  small,  as  only  the 
field  current  passes  through  them,  and  this  is  only  from  one  to 
two  per  cent  of  the  armature  current. 

There  is  still  another  type  of  alternating  current  generator  in 
which  the  wire  on  the  field  as  well  as  the  armature  is  held  station- 
ary. Such  machines  are  called  inductor  generators.  The  revolv- 
ing portion  of  such  generators  is  simply  a  mass  of  iron  formed 
like  a  very  large  pinion  with  correspondingly  large  teeth.  When 
this  part  revolves  the  ends  of  the  teeth  sweep  over  the  armature 
coils,  running  as  close  to  them  as  they  can  without  touching.  The 
magnetic  flux  developed  by  the  field  coil  issues  from  the  ends  of 
the  teeth  and  cuts  through  the  armature  coils  thus  inducing  e.m.fs. 
in  them.  It  will  be  seen  that  the  difference  between  this  type  of 


858 


HANDBOOK    ON    ENGINEERING. 


generators  and  the  revolving  armature  type  is  that  instead  of  re- 
volving the  armature  coils  through  the  stationary  field  flux,  the 
latter  is  revolved  and  the  armature  coils  are  held  stationary.  The 


Fig.  888.    Inductor  alternator. 

difference  between  the  inductor  generator  and  the  revolving  field 
type  is  that  in  the  latter  the  field  is  magnetized  by  a  number  of 
coils  and  these  are  rotated  together  with  the  field  poles,  while  in 
the  inductor  machine  there  is  a  single  field  magnetizing  coil  and 
this  remains  stationary,  the  part  that  revolves  being  what  might 
be  called  the  poles. 

An   inductor   alternator    is   shown    in  Fig.  388.     The  small 
machine  mounted  on  the  right  side  of  the  base  is  the  exciter  that 


HANDBOOK   ON    ENGINEERING.  859 

furnishes  the  field  magnetizing  current.  The  outer  casing  of  the 
machine  holds  a  ring  built  up  of  sheet  iron  laminations,  which 
constitutes  the  armature  and  supports  the  armature  coils.  The 
large  teeth,  or  polar  projections,  which  are  well  shown  in  the 
illustration,  are  carried  by  the  revolving  part,  and  when  rotating 
cause  the  magnetic  flux  to  sweep  over  the  armature  coils.  The 
field  coil  is  placed  back  of  these  polar  projections. 

Alternating  current  generators  are  run  singly,  or  they  may  be 
connected  in  parallel,  but  they  cannot  be  run  in  series.  If  an 
attempt  is  made  to  run  them  in  series,  one  of  the  machines  will 
act  as  a  motor  and  will  be  driven  by  the  current  generated  by  the 
other.  When  alternators  are  connected  in  parallel  it  is  necessary 
that  they  run  at  exactly  the  same  velocity,  if  they  are  identical 
in  construction.  If  the  generators  are  not  of  the  same  construe^ 
tion  then  their  velocities  will  depend  upon  the  number  of  poles 
each  one  has.  Machines  of  different  size  and  even  design,  can  be 
connected  in  parallel,  providing  the  frequency  of  the  currents 
they  generate  are  the  same.  To  make  the  frequency  the  same  it 
is  necessary  that  the  velocity  of  each  machine  multiplied  by  the 
number  of  poles  it  has  be  equal  to  the  same  number.  Thus  if 
one  machine  has  twice  as  many  poles  as  the  other,  it  must  run  at 
one-half  the  velocity.  The  velocity  of  alternators  connected  in 
parallel  must  be  equal,  absolutely,  and  not  practically  so ;  that 
is,  if  two  machines  are  alike,  and  one  runs  at  1000  revolutions 
per  minute,  the  other  must  run  at  1000  and  it  cannot  run  at  999 
or  1001.  Since  such  extreme  accuracy  in  speed  is  necessary  it 
might  be  inferred  that  it  is  practically  impossible  to  run  alter- 
nators in  parallel  unless  their  shafts  are  coupled  together,  or  they 
are  connected  through  spur  gearing  with  the  same  driving  shaft. 
As  a  matter  of  fact,  however,  alternators  can  be  run  in  parallel 
even  if  one  is  driven  by  a  steam  engine  and  the  other  by  a  water 
wheel,  and  they  may  be  side  by  side  or  several  miles  apart.  The 
reason  why  this  is  the  case  is  that  when  the  machines  are  in  oper- 


860  HANDBOOK   ON   ENGINEERING. 

ation,  the  current  holds  them  in  step.  If  several  generators  are 
feeding  into  the  same  circuit,  and  one  machine  tends  to  lag 
behind  the  others,  its  current  reduces  and  thus  the  speed  in- 
creases as  less  power  is  required  to  drive  it.  If  the  tendency  to 
lag  increases,  the  machine  begins  to  act  as  a  motor,  and  is  driven 
by  the  current  from  the  other  machines. 

While  it  is  possible  to  run  alternators  in  parallel  under  almost 
any  conditions  providing  they  are  speeded  so  as  to  generate  cur- 
rents of  the  same  frequency  and  nearly  the  same  voltage,  entirely 
satisfactory  results  cannot  be  obtained  unless  the  angular  motion 
is  uniform,  that  is,  unless  the  velocity  of  rotation  is  the  same  at 
all  points  of  the  revolution.  If  a  steam  engine  has  a  light  fly- 
wheel the  velocity  of  the  shaft  will  not  be  the  same  at  all 
points  of  the  revolution,  but  will  be  the  slowest  when  the 
crank  is  passing  the  center,  and  the  fastest  when  at  half  stroke. 
This  fact  is  clearly  shown  by  the  irregular  motion  of  the 
paddle-wheels  of  river  boats  driven  by  a  single  engine. 

If  two  alternators  are  driven  by  two  engines  whose  rotative 
motion  is  not  uniform  and  the  engines  are  so  timed  that  one 
is  on  the  center  when  the  other  is  at  half -stroke,  then  the 
action  of  the  two  alternators  will  be  irregular,  for  when  one 
machine  is  rotating  at  the  highest  velocity  the  other  will  be  ro- 
tating at  the  lowest.  This  uneven  action  of  the  alternators  may 
be  compared  with  the  work  of  two  horses  hitched  to  a  wagon  and 
pulling  unevenly.  If  both  horses  pull  together  all  the  time  the 
whiffle-tree  will  remain  straight  and  the  wagon  will  be  drawn 
along  smoothly ;  but  as  soon  as  the  horses  begin  to  pull  unevenly 
the  whiffle-tree  will  be  jerked  back  and  forth  and  the  motion  of 
the  wagon  will  be  irregular.  In  this  case  the  horses  soon  tire 
out  because  they  work  against  each  other  part  of  the  time.  The 
action  between  two  alternators  that  do  not  rotate  with  uniform 
velocities  is  practically  the  same  as  that  of  two  horses  that  do 
not  work  together ;  the  machine  that  runs  ahead  not  only  sends  a 


HANDBOOK   ON   ENGINEERING.  861 

current  into  the  main  circuit,  but  in  addition  backs  up  a  cur- 
rent through  the  other  generator,  thus  wasting  energy  by 
causing  a  strong  current  to  flow  back  and  forth  between  the  two 
machines.  To  overcome  this  difficulty  engines  made  to  drive 
alternators  are  provided  with  extra  heavy  flywheels,  so  that  the 
momentum  may  be  sufficient  to  keep  the  speed  up  to  the  normal 
point  while  the  crank  is  passing  the  center. 

With  small  alternators  that  have  only  a  few  poles  and  are 
driven  by  high-speed  engines,  the  affect  of  irregular  motion  is  not 
so  great  as  in  large  machines  having  many  poles,  hence  the  large 
slow-speed  engines  used  to  drive  alternators  having  a  large  num- 
ber of  poles,  must  be  provided  with  excessively  large  flywheels  to 
run  in  a  satisfactory  manner. 

The  reason  why  alternators  with  a  large  number  of  poles  require 
greater  regularity  in  motion  to  give  satisfactory  results,  can  be 
easily  understood.  Suppose  we  have  a  pair  of  two-pole  machines 
driven  by  engines  whose  flywheels  are  25  ft.  in  circumference. 
Suppose,  further,  that  the  irregularity  in  motion  is  such  that  each 
engine  when  running  at  the  faster  velocity,  gets  three  injches  ahead 
of  the  other.  Then  the  advance  in  position  will  be  one  per  cent, 
and  consequently  the  currents  of  the  two  generators  will  run 
ahead  and  behind  each  other  one  per  cent  at  each  quarter  of  a 
revolution.  Now,  if  these  same  two  engines  drive  two  twenty- 
pole  alternators,  then  the  irregularity  in  motion  will  be  multiplied 
ten  times,  because  one-tenth  of  a  revolution  will  give  one  cycle  of 
current,  and  the  current  of  each  machine  will  run  ahead  and  fall 
behind  the  other  ten  per  cent,  instead  of  one  per  cent. 

Starting"  alternators  connected  in  parallel :  —  In  starting  con- 
tinuous current  generators  that  are  connected  in  parallel  all  we 
have  to  do  is  to  set  one  machine  in  operation  and  then  after  the 
second  one  is  running  up  to  full  speed,  we  adjust  its  field  regu- 
lator until  the  voltage  is  the  same  as  that  of  the  first  machine,  or 
one  or  two  volts  higher.  We  then  throw  the  switch  and  connect 


862  HANDBOOK    ON   ENGINEERING. 

it  with  the  switchboard.  In  starting  alternators  that  are  con- 
nected in  parallel  we  have  to  do  more  than  this,  we  must  not  only 
adjust  the  second  machine  so  that  its  voltage  is  the  same  as  that 
of  the  first,  but  we  must  bring  it  up  to  the  proper  speed  and  get  its 
current  in  phase  with  that  of  the  first  generator  before  we  connect 
it  with  the  switchboard.  To  accomplish  all  this  with  certainty, 
devices  are  used  that  are  called  synchronizers,  or  phase  indicators. 
These  devices  consist  generally  of  a  couple  of  small  transformers 
one  of  which  is  connected  with  the  circuit  of  each  generator.  The 
secondary  wires  of  these  transformers  are  connected  with  each 
other  and  one  or  two  incandescent  lamps  are  connected  in  this 
circuit.  When  the  second  machine  is  started  up,  as  its  speed  is 
much  lower  than  that  of  the  generator  already  in  operation  the 
frequency  of  the  secondary  current  of  its  transformer  will  be  much 
lower  than  that  of  the  first  machine,  and  as  a  result  the  lamps  in 
the  circuit  of  the  two  transformers  will  flicker  rapidly.  As  the 
second  machine  builds  up  its  speed  the  flickering  of  the  lamps 
will  become  slower.  When  the  two  generators  are  running  at 
nearly  the  same  speed  the  flickering  will  be  replaced  by  rather 
long  periods  of  darkness  and  light.  During  the  periods  when  the 
lamps  are  lighted  the  current  generated  by  one  of  the  transformers 
is  in  such  a  direction  as  to  act  in  series  with  the  current  of  the 
other  and  thus  draw  the  current  through  the  lamp.  When  the 
lamps  are  dark  it  is  because  the  currents  of  the  two  transformers 
are  in  opposition  to  each  other  and  thus  no  current  passes  through 
the  lamps.  The  second  generator  is  connected  with  the  switch- 
board during  one  of  the  periods  of  darkness  or  brightness,  de- 
pending upon  the  way  in  which  the  transformers  are  connected. 
The  second  generator  will  not  be  running  at  exactly  the  proper 
speed  when  it  is  connected  with  the  switchboard,  but  as  soon  as 
it  is  connected  the  currents  of  the  two  machines  acting  upon  each 
other  will  at  once  draw  the  second  machine  into  step  with  the 
first  one,  and  they  will  continue  to  run  in  step  even  if  the  power 


HANDBOOK   ON   ENGINEERING. 


863 


driving  one  of  the  machines  should  fail.  In  the  latter  case,  the 
first  machine  would  not  only  furnish  current  for  the  main  cir- 
cuit, but  would  in  addition  drive  the  second  machine  as  a  motor. 
The  way  in  which  synchronizing  lamps  are  connected  in  single 
or  polyphase  circuits  is  clearly  illustrated  in  the  diagram  Fig.  389- 


To  Bus  Bars. 


Sy  nchr  oni  zing 


"To  GeneraCor. 


Fig.  389.    Showing  arrangement  of  synchronizing  lamps. 

The  three  upper  lines  are  connected  with  the  main  bus-bars  on 
the  switchboard  and  the  lower  lines  run  to  the  generator  that  is  to 
be  synchronized.  The  left  side  of  the  diagram  shows  the  connec- 
tions for  synchronizing  a  single-phase  generator.  In  such  a  case, 
the  middle  wire  running  to  the  bus-bars  and  to  the  generator  would 
not  be  used.  The  synchronizing  transformers  would  have  their 
primary  coils  connected  with  the  side  wires  in  the  manner  shown 
by  lines  //and  g  g.  When  the  generator  current  is  in  synchro- 
nism with  that  in  the  bus-bars,  the  primary  currents  in  the  two 
synchronizing  transformers  will  flow  in  the  direction  of  the  arrows 
a  a,  and  the  secondary  currents  will  be  in  the  direction  of  arrows 
c,  that  is,  in  opposition  to  each  other,  so  that  no  current  will  pass 
through  the  synchronizing  lamps.  If  the  connections  of  one  of 


864  HANDBOOK   ON    ENGINEERING. 

the  transformers  are  reversed,  either  in  the  primary  or  secondary, 
the  two  secondary  currents  will  flow  through  the  lamps  in  the  same 
direction  as  indicated  by  the  arrows  d  on  the  right  side  of  the 
diagram.  Thus  it  will  be  seen  that  the  synchronizing  lamps  can 
be  arranged  so  that  they  will  light  up  when  the  generator  current 
is  in  phase  with  the  bus-bar  current,  or  they  may  be  arranged  so 
as  to  be  dark  at  this  instant.  Generally  they  are  arranged  so  as 
to  be  bright  when  the  current  is  in  phase  and  the  switch  connect- 
ing the  generator  with  the  switchboard  is  closed  at  the  instant 
when  the  lamps  appear  to  be  brighter. 

When  two  and  three-phase  generators  are  started  up  the  first 
time  a  temporary  synchronizing  arrangement  is  connected  in  the 
manner  shown  on  the  right  side  of  Fig.  389.  The  synchronizing 
lamps  on  the  left  side  will  show  that  the  current  flowing  in  the 
two  side  wires  is  in  synchronism,  but  this  does  not  show  that 
the  other  currents  also  synchronize.  To  make  sure  that  the 
temporary  transformer  is  properly  connected  the  connections  e 
are  made  first,  and  if  the  lamps  on  both  sides  of  the  diagram 
become  dark  and  bright  together,  the'  connections  are  correct. 
The  connections  are  then  broken  and  are  transferred  to  the  middle 
wire  ;  then  when  all  the  currents  are  synchronized,  all  the  lights 
will  light  up  together.  Generally  the  internal  connections  of 
synchronizing  transformers  are  properly  made,  and  the  correct 
connection  of  the  terminal  wires  is  clearly  indicated  so  that  mis- 
takes in  making  connections  are  not  very  liable. 

Compensating  and  compounding  alternators* — Continuous 
current  generators  are  provided  with  a  compound  field  winding 
for  the  purpose  of  maintaining  the  voltage  uniform  as  the  arma- 
ture current  increases.  Alternating  current  generators  are 
compounded  for  the  same  purpose.  If  the  field  of  an  alternator 
is  excited  by  a  current  derived  from  an  exciter  the  voltage  of 
the  machine  will  drop  as  the  strength  of  the  current  generated  in 
the  armature  increases.  A  part  of  the  drop  is  due  to  the  fact 


HANDBOOK   ON   ENGINEERING.  865 

that  the  increased  current  absorbs  more  voltage  in  passing  through 
the  armature  coils.  The  balance  of  the  drop  is  produced  by 
the  reaction  of  the  armature  current  upon  the  field.  As  the 
current  of  the  exciter  that  magnetizes  the  field  remains  constant, 
the  magnetization  produced  .by  it  remains  constant.  The  cur- 
rent flowing  in  the  alternator  armature  acts  to  demagnetize  the 
field,  and,  as  its  action  increases  as  the  strength  increases  it 
follows  that  the  stronger  the  current  becomes  the  weaker  the 
field  will  be,  and,  as  a  result,  the  lower  the  voltage  of  the  cur- 
rent generated  in  the  alternator  armature. 

If  a  portion  of  the  current  of  the  alternator  armature  is  recti- 
fied by  being  passed  through  a  commutator  and  is  used  to  assist 
the  exciter  current  to  magnetize  the  field  then  the  field  magnetism 
will  increase  as  the  armature  current  increases,  because  the 
action  of  the  rectified  current  will  increase.  Thus  by  the  com- 
pound action  of  the  exciter  current  and  the  rectified  armature 
current,  the  magnetism  of  the  field  of  the  alternator  can  be  made 
to  increase  as  the  armature  current  increases,  and  in  this  way  the 
voltage  is  increased  so  as  to  compensate  for  the  greater  drop  of 
voltage  on  the  armature  coils,  the  result  being  that  the  voltage 
impressed  upon  the  wire  remains  practically  the  same  for  all 
strengths  of  current. 

The  above  results  can  be  obtained  providing  the  phase  relation 
between  the  current  and  the  impressed,  or  line  e.m.f.  does  not 
change ;  but  if  the  phase  relation  is  continually  changing  such 
perfect  regulation  cannot  be  realized.  The  reason  why  changes 
in  the  phase  of  the  current  interfere  with  the  regulation  is  that 
the  same  strength  of  armature  current  will  produce  different  de- 
grees of  reaction  on  the  field  magnetism  with  different  phase 
relations.  .If  the  lag  of  the  current  is  increased  the  reaction  upon 
the  field  will  be  increased,  and  in  like  manner  a  decrease  in  the 
lag  will  reduce  the  reaction  upon  the  field.  Several  arrangements 
are  used  for  obtaining  field  magnetizing  currents  that  will  com- 

55 


866  HANDBOOK    ON    ENGINEERING. 

• 

pensate  for  variations  in  the  lag  of  the  current  as  well  as  for  va- 
riations in  strength.  Alternators  provided  with  such  arrange- 
ments are  called  "  Compensated  Generators."  The  way  in  which 
a  field  magnetizing  current  is  obtained v that  will  compensate  for 
variations  in  lag  as  well  as  in  current  strength  is  by  using  a  por- 
tion of  the  armature  current  to  vary  the  strength  of  the  current 
generated  by  an  exciter,  the  exciter  being  provided  with  coils 
through  which  the  current  taken  from  the  armature  is  passed. 
These  coils  are  so  disposed  that  their  governing  action  upon  the 
exciter  is  proportional  to  the  lag  of  the  current  as  well  as  its 
strength,  hence  the  current  that  the  exciter  sends  through  the 
field  coils  of  the  alternator  is  at  all  times  sufficient  to  compensate 
for  variations  in  the  strength  and  phase  of  the  armature  current. 

If  an  alternator  is  single-phase,  one  commutator  is  sufficient  to 
rectify  the  portion  of  the  armature  current  and  to  magnetize  the 
field.  For  a  two-phase  machine,  two  commutators  are  required 
and  for  a  three-phase,  three  commutators.  To  obviate  using 
two  and  three  commutators  in  polyphase  generators,  trans- 
formers are  employed,  two  transformers  for  two-phase  and 
three  transformers  for  three-phase.  The  recording  currents 
of  these  transformers  are  combined  into  one,  and  this  com- 
bined current  is  passed  through  a  single  commutator  to  be  recti- 
fied. In  some  cases  only  one  of  the  currents  of  a  two  or  three- 
phase  generator  is  rectified,  but  with  most  machines,  if  they  are 
connected  in  parallel,  care  must  be  taken  to  have  the  circuits 
from  which  the  rectified  current  is  taken  properly  connected  with 
each  other ;  if  not,  one  armature  will  short  circuit  the  other. 
This  is  due  to  the  fact  that  when  alternators  are  run  in  parallel 
the  rectified  currents  for  the  field  coils  are  connected  with  each 
other  through  equalizer  wires,  in  a  manner  similar  to  that  used 
with  continuous  current  generators. 

The  ordinary  connections  for  two  generator's  in  parallel  are 
shown  in  the  diagram  Fig.  390. 


HANDBOOK   ON    ENGINEERING. 


867 


As  will  be  seen,  the  field-magetizing  currents  derived  from  the 
commutators  are  connected  with  each  other  through  the  equalizer 
switches,  hence,  to  avoid  short  circuiting  the  armature  through  the 
equalizer  connections,  if  the  commutator  rectify  one  current  only, 


Commutator 


Fig.  890.    Connections  of  composite    field  alternating  generators 
for  running:  in  parallel. 

the  two  rectified  currents  must  be  in  phase  with  each  other.  The 
rheostats  shown  in  each  field  circuit  are  for  the  purpose  of 
adjusting  the  voltage  of  each  generator  independently. 

The  use  of  transformers  to  transform  the  portion  of  the  arma- 
ture current  that  is  rectified  is  no  objection  against  polyphase 
machines,  because,  even  with  single  phases,  the  armature  voltage 
is  generally  so  high  that  a  transformer  is  used  so  as  to  obtain  a 
secondary  current  of  low  voltage  to  pass  through  the  field  coils. 

Alternating  current  motors*  —  From  the  foregoing  it  can  be 
understood  that  an  alternating  current  generator  can  be  used  as 
a  motor  providing  it  is  supplied  with  the  same  kind  of  currents, 


868  HANDBOOK   ON   ENGINEERING. 

that  is,  with  a  continuous  current  to  magnetize  the  field,  and  with 
an  alternating  current  for  the  armature.  A  single-phase  alter- 
nator will  run  as  a  motor  if  connected  in  a  single-phase  circuit. 
Two-phase  generators  will  act  as  two-phase  motors,  and  three- 
phase  generators  will  act  as  three-phase  motors.  With  either  one 
of  these  three  types  of  machines  a  continuous  current  will 
be  required  to  magnetize  the  field.  Two  and  three-phase  ma- 
chines can  be  run  with  a  single  alternating  current,  by  connect- 
ing one  of  the  armature  circuits  only,  or  all  the  circuits  may  be 
used  if  they  are  connected  in  parallel. 

When  an  alternator  is  used  as  a  motor  it  is  called  a  synchro- 
nous motor,  because  it  runs  in  synchronism  with  the  generator 
that  supplies  the  current.  A  simple  alternator  (single-phase  ma- 
chine) becomes  a  single-phase  synchronous  motor,  and  a  two 
or  three-phase  generator  becomes  a  two  or  three-phase  syn- 
chronous motor. 

A  single-phase  synchronous  motor  will  not  start  up  of  its  own 
accord,  but  must  be  set  in  motion  and  run  up  to  nearly  its  full 
speed  before  it  will  begin  to  act  as  a  motor.  If  it  is  started  up 
without  a  load  when  it  comes  rather  near  to  its  full  speed  it  will 
give  a  sudden  jump  and  swing  into  step  with  the  current  and  then 
continue  to  run  at  this  velocity.  If  it  is  started  with  a  full  load 
it  will  not  fall  into  step  with  the  current  until  its  speed  is  very 
nearly  up  to  the  proper  point.  Synchronous  motors  are  never 
started  under  load,  they  are  always  started  light. 

Two  and  three-phase  synchronous  motors  can  be  started  with- 
out outside  assistance.  Synchronous  motors  are  generally  pro- 
vided with  a  self -starting  motor,  to  set  them  in  motion,  or  else 
they  are  arranged  so  as  to  be  self -starting  by  being  converted, 
in  the  act  of  starting,  into  some  form  of  motor  that  is  self- 
starting. 

Fig*  39  \  shows  a  synchronous  motor  of  large  size  provided 
with  an  induction  motor  of  much  smaller  capacity  to  start  it. 


HANDBOOK    ON    ENGINEERING. 


869 


This  motor  is  of  .the  revolving  field  type,  and,  as  will  be  seen,  is 
precisely  the  same  as  the  same  type  of  generator. 


Fiff.  391.    1000  h.  p.  two-phase  revolving  field  synchronous  motor. 


Owing  to  the  fact  that  synchronous  motors  are  not  self -starting, 
they  are  generally  used  only  where  large  power  is  required,  unless 
they  happen  to  be  made  so  as  to  be  self -starting,  then  they  are 
used  in  small  sizes. 

A  synchronous  motor,  when  running,  will  keep  in  step  with  the 
current,  no  matter  how  much  the  load  may  vary,  provided  it  is 
not  made  greater  than  the  capacity  of  the  machine.  If  the  load 
is  made  so  great  that  the  motor  cannot  carry  it,  the  armature 
will  be  pulled  out  of  step  with  the  current  and  will  imme- 
diately come  to  a  stop.  On  this  account,  motors  of  the 
synchronous  type  are  not  well  adapted  to  operate  cranes  or  similar 
machines  in  which  there  is  a  liability  of  greatly  overloading  the 
machine  occasionally. 


870  HANDBOOK    ON    ENGINEERING. 

The  current  developed  by  an  alternating  current  generator  will 
lag  behind  the  impressed  e.m.f.  as  has  been  fully  explained  in  the 
foregoing.  If  this  current  is  passed  through  a  second  machine,  that 
acts  as  a  motor,  the  latter  will  tend  to  generate  a  current  that  flows 
in  opposition  to  that  of  the  generator  ;  hence,  in  this  current  the  lag 
will  be  in  the  opposite  direction  of  that  of  the  current  that  drives 
it.  That  is  when  the  machine  acts  as  a  motor  its  whole  action  as 
a  generator  is  reversed.  Owing  to  this  fact,  if  a  synchronous 
motor  is  placed  at  one  end  of  a  circuit,  and  a  generator  at  the 
other,  the  motor  will  act  to  neutralize  the  self-induction  of  the 
generator,  and  thus  to  bring  the  current  in  the  circuit,  and  the 
impressed  e.m.f .  into  phase  with  each  other.  Thus,  a  synchro- 
nous motor  can  be  made  to  act  in  the  same  way  as  a  condenser, 
to  reduce  the  lag  of  the  current. 

Power  factor* — In  an  alternating  current  circuit,  it  is  very 
important  to  reduce  the  lag  of  the  current  as  far  as  possible 
because  the  actual  amount  of  energy  carried  by  the  current  depends 
upon  the  angle  of  lag,  as  was  fully  explained  in  connection  with 
Figs.  372  to  374.  In  a  continuous  current  circuit  the  power  is 
always  equal  to  the  product  of  the  volts  by  the  amperes, 
but  in  an  alternating  current  circuit  this  product  is  not  a 
measure  of  the  power.  It  is  called  the  apparent  power,  or  the 
volt-amperes.  The  actual  power  is  equal  to  the  amperes  multi- 
plied by  the  e.m.f.  in  phase  with  the  current,  or  the  active  voltage, 
as  it  is  called.  The  ratio  between  the  true  power  and  the  volt- 
amperes  is  called  the  power  factor.  The  power  factor  can  be 
obtained  by  dividing  the  true  power  by  the  volt-amperes,  and  it 
may  range  from  100  per  cent  when  the  current  and  impressed 
e.m.f.  are  in  phase  down  to  five  or  ten  per  cent  when  the  angle  of 
lag  is  nearly  90  per  cent.  In  actual  working  circuits  the  power 
factor  ranges  between  about  95  and  75  per  cent.  Any  kind  of 
device  that  has  a  low  reactance,  as,  for  example,  incandescent 
lamps,  acts  to  keep  the  angle  of  lag  of  the  current  small,  and  thus 


HANDBOOK   ON    ENGINEERING.  871 

the  power  factor  high.  Devices  having  large  reactance,  such  as 
transformers,  and  induction  motors  act  to  increase  the  angle  of 
lag  of  the  current,  and  thus  to  reduce  the  power  factor.  Devices 
that  develop  a  negative  reactance,  that  is,  which  cause  the  current 
to  lead  the  impressed  e.m.f.,  such  as  condensers  and  synchronous 
motors,  can  be  used  in  circuits  in  which  transformers  and  similar 
devices  are  operated  so  as  to  counteract  these  and  thereby  keep 
up  the  percentage  of  the  power  factor. 

Induction  and  other  types  of  motors*  —  In  addition  to  the 
synchronous  motors  just  explained,  the  only  type  of  machine  that 
requires  notice  here  is  the  induction  motor.  This  is  by  far  the 
most  extensively  used  of  all  alternating  current  motors,  and  from 
the  manner  in  which  it  acts  it  has  a  greater  range  of  adaptability 
than  any  other  type.  It  may  be  well  to  mention  here,  however, 
that  a  plain  motor,  such  as  those  used  with  continuous  currents, 
can  be  made  to  operate  with  alternating  currents  providing  the 
field  cores  are  made  laminated,  instead  of  solid  castings.  If  the 
field  is  solid  the  motor  will  not  run  if  connected  in  an  alternating 
current  circuit  because  the  large  mass  of  iron  constituting  the  field 
cannot  be  magnetized  and  demagnetized  as  fast  as  the  current 
alternates.  If  we  take  hold  of  a  freight  car  and  try  to  shake  it 
we  will  fail  in  the  effort,  simply  because  the  bulk  is  too  great  to 
be  set  in  motion  rapidly.  If,  however,  we  take  hold  of  the  side 
of  a  light  buggy  and  shake  it  we  will  be  able  to  produce  a  very 
vigorous  movement,  simply  because  the  bulk  is  light.  In  the 
same  way,  if  we  attempt  to  alternate  the  magnetic  polarity  of 
large  masses  of  iron  >re  fail  because  the  bulk  is  too  great,  but  if 
we  divide  the  mass  up  into  many  thin  sheets  we  will  have  no  diffi- 
culty in  causing  its  polarity  to  change  rapidly.  Alternating  cur- 
rent motors  of  this  kind  which  are  called  commutator  motors, 
have  been  made,  but  they  are  not  used  or  manufactured  for  com- 
mercial purposes  at  the  present  time,  because  they  are  far  inferior 
to  other  types.  They  are  open  to  two  objections,  one  of  which 


872 


HANDBOOK    ON    ENGINEERING. 


is  that  they  spark  considerably  and  the  other  is  that  they  will  not 
give  much  more  than  one-third  the  power  that  the  same  machine 
will  develop  if  supplied  with  a  continuous  current.  The  reason 
why  they  give  such  small  power  is  that  on  account  of  the  many 
turns  of  wire  on  the  field  the  inductive  action  is  very  great,  hence 
the  reactance  is  very  high,  and  as  a  result  the  current  lags  exces- 
sively so  that  the  power  factor  is  very  low,  therefore,  although  the 
current  is  strong,  the  actual  energy  carried  by  it  is  comparatively 
small.  Several  other  types  of  alternating  current  motors  have 
been  devised,  but  they  have  never  got  beyond  the  experimental 
stage. 

Principle  of  the  induction    motor- — Induction   motors  are 
made  for  single  and  polyphase  currents.     When  in  operation  the 


392  and  393.    Principle  of  induction  motor. 

principle  of  action  is  the  same  in  all,  but  in  the  act  of  starting  the 
single-phase  machine  is  different  from  the  others.  Single-phase 
induction  motors  will  not  start  of  their  own  accord  unless  provided 
with  special  starting  arrangements.  The  most  common  way  of 
arranging  a  single-phase  induction  motor  so  as  to  be  self-starting 
is  to  provide  a  set  of  starting  coils  that  virtually  convert  it  into  a 


HANDBOOK   ON   ENGINEERING.  873 

two-phase  machine  in  the  act  of  starting.  When  the  motor  is 
underway  the  starting  coils  are  cut  out,  although  in  some  cases 
they  are  left  in  circuit  all  the  time.  The  principle  of  the  induc- 
tion motor  can  be  explained  by  the  aid  of  the  diagrams  Figs. 
392  to  395.  These  diagrams  illustrate  the  action  in  a  two-phase 
machine,  which  is  the  one  most  easily  understood.  The 
single-phase  induction  motor  is  the  most  difficult  one  to  ex- 
plain or  to  understand,  so  we  will  leave  it  for  the 
last.  In  an  induction  motor,  the  stationary  part,  which  is 
called  the  stator,  and  sometimes  the  field,  is  provided  with  coils 
that  are  connected  with  the  operating  circuits.  The  rotating  part, 
which  is  called  the  rotor,  and  sometimes  the  armature,  is  provided 
with  coils  that  are  short  circuited  upon  themselves  and  are  not 
connected  with  the  operating  circuits.  The  principle  of  operation 
generally  stated  is  that  the  currents  in  the  stator  develop  an  in- 
ductive action  upon  the  coils  of  the  rotor  thus  developing  currents 
in  these,  the  action  being  substantially  the  same  as  that  in  a 
transformer.  On  that  account  the  stator  is  also  called  the 
primary  member,  while  the  rotor  or  armature  is  commonly  called 
the  secondary  member.  The  primary  currents  passing  through 
the  coils  of  the  stator,  develop  a  magnetic  flux  and  the  secondary 
currents  induced  in  the  coils  of  the  rotor  also  develop  a  magnetic 
flux,  these  two  fluxes  are  at  an  angle  with  each  other,  and,  hence, 
there  is  a  strong  attraction  exerted  between  them,  the  magnetism 
of  the  rotor  making  an  effort  to  place  itself  parallel  with  that  of 
the  stator.  The  magnetism  of  the  stator  rotates,  on  account  of 
being  developed  by  alternating  currents,  and  the  magnetism  of 
the  rotor  in  trying  to  place  itself  parallel  with  that  of  the  stator 
also  rotates,  chasing  the  latter  around  the  circle  but  never 
overtaking  it. 

In  Fig.  392  let  A  A  represent  two  coils  connected  in  one  of  the 
circuits  of  a  two-phase  system,  and  let  B  B  represent  two  other 
coils  connected  in  the  other  circuit  of  this  same  system.  Suppose 


874 


HANDBOOK   ON   ENGINEERING. 


we  consider  the  instant  of  time  when  the  current  flowing  through 
the  A  A  coils  is  at  its  maximum  value,  then  at  this  very  same  instant 
the  current  in  the  B  B  coils  will  be  zero.  The  current  in  the  A  A 
coils  is  then  the  only  magnetizing  current  acting  upon  the  ring  at 
this  instant.  Suppose  the  direction  of  the  current  through  A  A 
is  such  as  to  develop  a  magnetic  flux  that  will  traverse  the  space 
in  the  center  of  the  ring  in  the  direction  of  arrow  C.  As  the 
current  in  the  A  A  coils  begins  to  decrease,  that  flowing  in  the 
B  B  coils  will  begin  to  increase.  Let  the  direction  of  the  current 
in  the  B  B  coils  be  such  as  to  send  a  magnetic  flux  through  the 
center  of  the  ring  in  the  direction  of  arrow  C  in  Fig.  394.  This 
magnetization  will  act  upon  that  developed  by  the  current  in  the 
A  A  coils  and  will  have  a  tendency  to  twist  it  around  into  the 
direction  of  arrow  C  in  Fig.  393.  When  the  current  in  the  .4  A 
coils  has  reduced  and  the  current  in  the  B  B  coils  has  increased 
until  they  are  both  equal,  then  each  one  will  act  with  equal  force 


Figs.  394:  and  395.    Illustrating  operation  of  induction  motor. 

to  establish  a  magnetization  in  its  own  direction,  and  the  result 
will  be  that  the  actual  direction  of  the  magnetic  flux  will  be  as 
indicated  by  arrow  C  in  Fig.  393.  Thus  we  see  that  by  the 
decrease  in  the  strength  of  the  current  in  the  A  A  coils  and  the 


HANDBOOK   ON    ENGINEERING.  875 

increase  in  the  strength  of  the  current  in  the  B  B  coils  until  they 
are  both  equal,  the  magnetic  flux  has  been  rotated  from  the 
position  of  arrow  C  in  Fig.  392  to  its  position  in  Fig.  393.  Now 
as  the  variation  in  the  currents  progresses,  and  that  in  A  A 
becomes  weaker,  while  that  in  B  B  becomes  stronger,  the 
direction  of  the  magnetic  flux  will  be  still  further  rotated  so  that 
when  the  current  in  B  B  reaches  the  maximum  value,  and  that  in 
A  A  becomes  zero,  the  direction  of  the  flux  will  be  that  of  arrow 
C  in  Fig.  394.  As  we  advance  beyond  this  instant  of  time,  the 
current  in  B  B  will  begin  to  reduce,  while  that  in  A  A  will  begin 
to  increase,  but  its  direction  will  be  the  opposite  of  what  it  was 
iii  Fig.  392,  so  that  when  the  currents  in  the  two  sets  of  coils 
become  equal  again,  the  direction  of  the  magnetic  flux  will  be 
that  of  arrow  0  in  Fig.  395.  When  the  current  in  the  A  A  coils 
reaches  the  maximum  and  that  in  B  B  becomes  zero,  the  flux  will 
have  rotated  through  one-half  of  a  revolution  and  arrow  G  will 
be  in  the  vertical  position  but  pointing  downward. 

If  we  follow  the  action  of  the  currents  further  we  will  find  that 
as  a  result  of  the  continuous  increasing  and  decreasing  and 
changing  of  direction,  the  magnetic  flux  indicated  by  arrow  C 
will  continuously  rotate  keeping  time  with  the  frequency  of  the 
currents.  Now  if  we  suppose  that  an  armature  upon  which  a 
number  of  coils  are  wound  in  a  diametrical  position,  is  placed 
.  within  the  field  ring,  and  is  held  stationary,  we  will  see  at  once 
that  the  rotating  magnetic  flux  will  cut  through  its  coils  and 
develop  e.m.fs.  in  them.  The  currents  developed  in  these  coils 
on  the  stationary  armature  will  be  alternating,  hence,  they  will 
develop  a  magnetic  flux  in  the  armature  that  will  rotate,  and 
keep  time  with  the  rotating  flux  developed  by  the  field  coils. 
Both  these  fluxes  act  inductively  upon  the  field  and  armature 
coils,  their  combined  effect  being  equal  to  that  of  a  single  flux 
located  90  degrees  in  advance  of  the  e.m.f.  induced  in  the 
armature  coils,  hence,  somewhat  more  than  90  degrees  ahead  of 


876  HANDBOOK    ON    ENGINEERING. 

• 

the  armature  current.  If  we  hold  the  armature  by  means  of  a 
brake,  and  free  this  slightly,  so  that  the  armature  may  revolve 
slowly,  it  will  at  once  follow  around  after  the  rotating  field,  but 
as  its  magnetization  is  developed  by  currents  that  are  induced  by 
the  action  of  the  field  magnetism,  it  will  matter  little  how  fast 
the  armature  may  revolve,  its  magnetization  will  never  be  able  to 
overtake  that  of  the  field. 

As  can  be  judged  from  the  foregoing  explanation,  an  induction 
motor  is  not  a  synchronous  machine,  and  its  armature  can  never  at- 
tain a  velocity  equal  to  that  of  the  rotating  field.  If  the  resistance 
of  the  armature  coils  is  made  very  low,  it  may  reach  a  velocity 
very  near  to  that  of  the  rotating  flux.  The  difference  between  the 
velocity  of  the  rotating  flux  and  that  of  the  rotating  armature  is 
called  the  slip  of  the  motor. 

If  the  motor  is  designed  for  constant  speed,  the  resistance  of 
the  armature  coils  is  made  very  low,  and  then  when  the  machine  is 
running  free,  the  speed  of  the  armature  may  run  up  to  99  or  99£ 
per  cent  of  the  speed  of  the  rotating  field,  and  when  the  maximum 
load  is  put  on  it  may  not  drop  lower  than  94  or  95  per  cent.  If 
a  motor  is  designed  in  this  way  the  pull  of  the  armature  when  it 
starts  up  will  be  small  and  will  gradually  increase  until  the  speed 
is  about  nine-tenths  of  the  maximum  when  it  will  again  begin  to 
decrease. 

If  it  is  desired  to  make  a  motor  that  will  give  a  strong  pull 
when  it  starts  up,  its  armature  coils  must  have  more  resistance, 
and  then  it  will  pull  harder  on  the  start,  but  as  fast  as  the  speed 
builds  up  the  pull  will  reduce.  From  this  it  will  be  seen  that  in- 
duction motors  that  are  made  so  as  to  run  at  nearly  a  constant 
speed,  say  to  vary  five  or  six  per  cent  between  full  load  and  run- 
ning free,  will  not  give  a  strong  pull  in  the  act  of  starting,  hence 
they  will  have  to  be  started  without  a  load.  If  a  motor  is  to  be 
made  to  start  under  a  full  load  it  must  be  proportioned  so  that  it 
will  not  run  at  a  constant  speed,  but  will  gradually  reduce  its 
velocity  as  the  load  is  increased. 


HANDBOOK   ON    ENGINEERING.  877 

Induction  motors,  if  very  small,  are  started  by  connecting 
them  directly  with  the  operating  circuits,  but  if  they  are  of  any 
capacity  they  must  be  provided  with  some  kind  of  starting  resist- 
ance so  as  to  keep  the  starting  current  down  within  safe  limits. 
One  way  of  starting  is  to  introduce  resistance  into  the  primary 
circuits,  but  this  results  in  reducing  the  strength  of  the 
field,  and  thus  the  pull  of  the  armature.  Another  way  is  to  intro- 
duce resistance  into  the  armature  coil  circuit.  This  is  the  best 
method,  because  it  enables  the  motor  to  start  up  with  a  strong 
pull. 

Three-phase  induction  motors  act  in  precisely  the  same  way  as 
the  two-phase,  the  only  difference  being  that  the  rotation  of  the 
field  flux  is  produced  by  the  increase  and  decrease  in  the  strength 
of  three  currents  flowing  through  three  sets  of  coils  equally 
spaced  around  the  circle  instead  of  by  the  increase  and  decrease 
in  two  currents  flowing  in  two  sets  of  coils  equally  spaced  around 
the  circle. 

In  the  single-phase  induction  motor,  the  magnetic  flux  developed 
by  the  single  alternating  current  traversing  a  single  set  of  coils  on 
the  field  combines  with  the  magnetic  flux  developed  by  the  armature 
current,  to  develop  a  rotating  field  and  this  acting  upon  the  armature 
coils  produces  rotation  in  precisely  the  same  way  as  in  the  two- 
phase  machine.  This  is  the  action  that  takes  place  after  the 
armature  is  set  in  motion,  but  if  the  load  is  increased  and  the 
armature  speed  is  reduced  the  rotating  field  begins  to  become 
irregular,  and  by  the  time  the  armature  velocity  is  reduced  to 
about  one-half,  the  rotating  flux  becomes  so  irregular  in  its  move- 
ment, that  the  armature  pull  begins  to  reduce  very  rapidly,  and 
the  machine  comes  to  a  standstill.  Owing  to  this  fact  single- 
phase  induction  motors  cannot  be  used  in  cases  where  it  is  de- 
sired to  start  with  a  strong  pull,  or  where  a  wide  range  of  speed 
variation  is  desired. 

To  make  a  single-phase  induction  motor  self -starting,  it  is  wound 


878  HANDBOOK    ON    ENGINEERING. 

with  two  sets  of  coils,  like  the  diagrams  Figs.  392  to  395,  and  the 
current  from  the  single-phase  circuit  is  passed  through  these  two 
sets  of  coils  in  parallel  branches,  and  in  one  of  the  branches  the 
reactance  is  greatly  increased,  so  as  to  make  the  current  in  this 
branch  lag  much  more  than  in  the  other.  In  this  way  a  phase 
displacement  is  obtained  between  the  two  currents,  and  this  pro- 
duces a  corresponding  displacement  in  the  magnetic  fluxes  devel- 
oped by  the  two  sets  of  coils,  so  that  their  combined  action 
develops  a  rotating  field.  This  field  does  not  rotate  at  a  uniform 
rate,  like  the  field  of  a  two-phase  motor,  but  it  is  uniform  enough 
for  the  purpose  of  setting  the  machine  in  motion.  To  increase 
the  reactance  in  the  auxiliary  starting  coils,  all  that  is  necessary 
is  to  wind  them  with  many  turns  of  fine  wire,  and  this  is  an 
arrangement  very  commonly  employed,  but,  in  some  cases,  sep- 
arate coils  are  placed  in  the  auxiliary  circuit  to  obtain  the  required 
reactance. 

There  are  other  ways  in  which  single-phase  induction  motors 
are  made  self -star  ting,  but  they  are  not  very  extensively  used. 

While  induction  motors  are  very  satisfactory  machines,  being 
adapted  to  every  kind  of  work,  even  to  the  operation  of  railway 
cars,  they  have  the  objection  of  being  highly  inductive  devices 
that  act  to  greatly  increase  the  lag  of  the  current,  and  thereby  to 
reduce  the  power  factor.  On  this  account  they  are  often  used  in 
connection  with  synchronous  motors  so  that  the  latter  may  coun- 
teract their  inductive  effect,  and  thus  keep  the  power  factor  high. 

The  small  motor  shown  in  Fig.  391,  is  an  induction  motor. 
Induction  motors  are  made  in  many  different  designs,  and  as 
large  as  300  to  400  H.  P.,  but  as  a  rule  they  are  confined  to  much 
smaller  capacities ;  synchronous  motors  being  used  for  the  larger 
sizes. 

Rotary  transformers  and  rotary  converters*  —  A  rotary 
transformer  is  a  machine  by  means  of  which  a  continuous  current 
may  be  obtained  from  an  alternating  current.  A  rotary  con- 


HANDBOOK    ON    ENGINEERING. 


879 


verier  is  a  machine  for  accomplishing  the  same  result.  The 
essential  difference  between  the  two  is  that  the  first  is  driven  by 
an  alternating  current  and  generates  a  continuous  current,  while 
the  second  changes  an  alternating  into  a  continuous  current.  As 
a  result  of  this  difference  the  rotary  transformer  can  be  used  to 
obtain  a  continuous  current  of  any  desired  voltage  from  an 
alternating  current  of  any  given  voltage  ;  but  in  the  rotary  con- 
verter, as  the  action  is  to  convert  the  alternating  into  a  con- 
tinuous current,  the  voltage  relation  is  fixed  so  that  for  a  given 
alternating  current  voltage  we  will  get  a  corresponding  contin- 
uous current  voltage.  Both  these  machines  can  be  used  in  the 
reverse  order,  that  is  to  transform  or  convert  a  continuous  into  an 
alternating  current. 


B 


Fig.  396.    Principle  of  the  rotary  transformer. 

Principle  of  the  rotary  transformer* — The  principle  of  the 
rotary  transformer  is  illustrated  in  Fig.  396.  In  this  diagram  A 
represents  a  continuous  current  armature,  and  B  is  an  alternating 
current  armature.  If  both  these  are  provided  with  suitable 
magnetic  fields  then  if  continuous  current  is  passed  through  A  it 
will  become  a  motor  and  will  drive  B  and  generate  therein  a 
single  alternating  current  or  a  number  of  them  according  to  the 
way  in  which  the  armature  is  wound.  Thus  B  may  become  a 
single  or  a  polyphase  generator.  It  can  further  be  seen  that  the 


880 


HANDBOOK   ON  ENGINEERING. 


voltage  of  the  currents  generated  by  B  is  in  no  way  connected 
with  the  voltage  of  the  current  that  drives  A,  and  depends  wholly 
upon  the  way  in  which  B  is  wound.  If  B  is  connected  with  an 
alternating  current  circuit,  then  it  will  run  as  a  synchronous 
motor  and  drive  A  and  the  latter  will  generate  a  continuous 
current.  This  machine  if  driven  by  a  continuous  current  will  be 
self -starting,  but  if  driven  by  an  alternating  current  it  will  have 
to  be  started.  If  driven  by  an  alternating  current  its  speed  will 
be  controlled  by  the  frequency  of  the  current,  but  if  driven  by  a 
continuous  current  its  speed  will  vary  with  the  magnitude  of  the 
load  placed  upon  it. 


b 

0 

/ 

c 

5  C 

Ml 

C 

A 

/ 

y  /* 

u\ 

Us      l*> 

Figs.  397  and  398.    Principle  of  the  rotary  converter. 

Figs.  397  and  398  illustrate  the  principle  of  operation  and  the 
construction  of  a  rotary  converter.  The  armature  A  is  of  the 
continuous  current  type,  having  a  commutator  C.  If  it  is  a  two- 
pole  machine,  then  if  wires  are  connected  with  diametrically 
opposite  segments  of  the  commutator  as  is  indicated  in  Fig.  398 
by  the  arrows,  and  these  are  connected  with  the  collector  rings 
a  a,  brushes  c  c  placed  on  these  rings,  will  take  of  a  true  alter- 
nating current  if  the  armature  is  placed  in  a  suitable  field  and  is 
driven.  While  alternating  current  can  be  taken  from  the  brashes 
C  c,  a  continuous  current  can  also  be  taken  from  the  brushes  b  &, 


HANDBOOK  OK  ENGINEERING.  881 

jyhich  bear  upon  the  commutator  C.  Thus,  this  machine,  if 
driven,  becomes  a  combination  generator  which  will  deliver  a 
continuous  and  an  alternating  current  at  the  same  time. 
Machines  of  this  type  are  constructed  and  are  called  double 
current  generators. 

If  the  brushes  c  c  are  connected  with  a  single-phase  circuit, 
and  the  armature  is  placed  in  a  suitable  field,  it  will  rotate  and 
from  the  b  b  brushes  of  the  commutator  a  continuous  current 
can  be  drawn.  If  the  brushes  b  b  are  connected  with  a  continu- 
ous current  circuit,  an  alternating  current  will  be  delivered 
through  the  brushes  c  c. 

If  four  wires  are  connected  with  four  commutator  segments  one 
quarter  of  the  circumference  apart,  and  these  are  connected  with 
four  collector  rings,  then  from  these  rings  two  alternating  cur- 
rents 90  degrees  out  of  phase  can  be  obtained.  Thus,  with  four 
connections  with  the  commutator  segments  the  machine  can 
convert  two -phase  currents  into  one  continuous  current,  or  one 
continuous  current  into  two-phase  currents,  that  is  into  two  alter- 
nating currents  90  degrees  out  of  phase. 

If  wires  are  connected  with  three  commutator  segments  one- 
third  of  the  circumference  apart,  and  these  are  connected  with 
three  collector  rings,  then  the  machine  will  become  a  three-phase 
converter,  and  if  connected  with  a  three-phase  system  will  deliver 
one  continuous  current  or  if  connected  with  a  continuous  current 
circuit  will  deliver  the  three  currents  of  a  three-phase  system. 

The  rotary  converter,  as  will  be  seen  from  the  foregoing, 
actually  changes  a  continuous  current  into  one  or  more  alternat- 
ing currents,  or  one  or  more  alternating  currents  into  one  con- 
tinuous current,  and  in  every  case  there  is  a  direct  electrical  con- 
nection between  the  continuous  and  the  alternating  current  cir- 
cuits. As  this  type  of  machine  simply  converts  the  current  of 
one  type  into  current  of  the  other  type  it  is  quite  evident  that 
there  must  be  a  fixed  relation  between  the  strength  of  the  alternat- 

56 


882  HANDBOOK   ON   ENGINEERING. 

ing  and  continuous  currents  and  also  between  the  voltages.  An 
alternating  current  if  of  the  sine  type,  will  have  an  effective  value 
of  70.7  per  cent  of  its  maximum  value,  for  the  amperes  as  well  as 
the  volts.  So  that  if  we  have  a  continuous  current  of  70.7 
amperes  and  70.7  volts,  we  must  have  an  alternating  current  of 
100  amperes  maximum  value  and  100  volts  maximum  value  to  be 
equal  to  it,  and  if  the  energy  is  also  to  be  equal,  the  current  in 
the  alternating  current  circuit  must  be  in  phase  with  it  e.m.f., 
that  is  the  power  factor  must  be  100. 

In  a  rotary  converter  the  voltage  of  the  continuous  current  is 
equal  to  the  maximum  voltage  of  the  alternating  current  and  the 
strength  of  the  continuous  current  is  equal  to  one-half  the  maxi- 
mum strength  of  the  alternating  current.  Thus  if  the  maximum 
voltage  of  the  alternating  current  is  1,000  volts,  the  voltage  of  the 
continuous  current  will  be  1,000,  and  if  the  maximum  strength  of 
the  alternating  current  is  100  amperes  the  strength  of  the  contin- 
uous current  will  be  50  amperes.  This  arises  from  the  fact  that 
the  rotary  converter  does  not  develop  energy,  as  it  drives  itself, 
hence,  the  energy  in  the  continuous  current  cannot  be  more  than 
that  in  the  alternating,  in  fact  it  will  be  a  trifle  less  owing  to  the 
energy  absorbed  in  driving  the  machine.  Now  if  the  alternating 
e.m.f.  and  current  have  the  maximum  values  of  1,000  volts  and 
100  amperes,  their  effective  values  will  be  707  volts  and  70.7 
amperes,  and  the  product  of  these  two  will  be  the  energy  in  watts. 
Thus  707  X  70.7  =  50,000  watts.  Now  if  the  voltage  of  the 
continuous  current  is  1,000,  its  strength  must  be  50  amperes,  less 
the  amount  absorbed  in  overcoming  the  friction  of  the  machine. 

Fig.  399  shows  a  rotary  converter  of  large  size. 

Alternating  current  distributions*  —  The  principal  advantage 
of  alternating  over  continuous  currents  is  that  they  can  be  used 
for  transmitting  energy  to  much  greater  distances,  owing  to  the 
fact  that  a  high  voltage  can  be  used  to  transmit  the  main  current 
over  the  wire,  and  at  the  receiving  end  this  current  can  be  passed 


HANDBOOK   ON   ENGINEERING. 


883 


through  transformers,  from  which  secondary  currents  of  low  volt- 
age may  be  obtained.     In  a  few  instances,  low  voltage  alternating 


Fig.  399.    Rotary  converter. 

currents  are  used  for  distributing  current  over  small  areas.  The 
general  arrangement  of  circuits  and. apparatus  for  a  three-phase 
system  of  this  kind  is  illustrated  in  the  diagram  Fig.  400. 


B 


Fig.  400.    General  arrangement  of  three-phase  system. 

The  generator  is  shown  at  the  extreme  left.  At  A  an  induction 
motor  is  connected  with  the  circuit.  At  B  an  "  arc  "  light  is 
corrected  in  the  secondary  circuit  of  a  small  transformer.  At  G 


884 


HANDBOOK   ON   ENGINEERING. 


a  number  of  incandescent  lamps  are  connected.  At  D  the  circuit 
is  used  to  drive  a  rotary  transformer,  which  develops  a  continuous 
current  to  charge  storage  batteries  at  E.  The  three  solid  line 
wires  constitute  the  main  circuit  and  all  the  apparatus  is 
connected  with  them.  The  broken  line  above  these  is  the 
neutral  wire  and  is  connected  with  the  incandescent  lamps 
only.  If  the  number  of  these  lamps  in  each  circuit  is  the 
same,  as  is  shown  on  the  diagram,  no  current  will  pass  to  the 
neutral  wire,  but  if  in  one  of  the  circuits  there  are  more  lamps 
t,han  in  the  other,  the  excess  of  current  will  pass  to  or  from  the 
,ieutral  wire.  Systems  of  this  type  are  operated  at  voltages  rang- 
ing between  200  and  600. 


Fig,  401.    Arrangement  for  distances  up  to  four  miles. 

The  diagram,  Fig.  401,  shows  the  way  in  which  the  circuits  are 
arranged  when  the  distance  of  transmission  is  from  one  to  three 
or  four  miles.  For  such  cases,  the  voltage  generally  used  is 
2300.  The  generator  at  the  left  develops  currents  that  pass 
directly  to  the  main  line.  At  A  an  induction  motor  is  connected 
directly  to  the  main  line.  At  B  transformers  are  used  to  develop 
secondary  currents  of  low  voltage  to  supply  the  circuit  wires  C 
from  which  the  motor  D  and  incandescent  lamps  E  are  fed.  At  F 
a  series  transformer  is  used  to  develop  a  secondary  current  of 
constant  strength  to  operate  the  arc  lamps  G.  The  difference  be- 
tween a  series  transformer  and  the  ordinary  type  is  that  the 
former  is  provided  with  a  mechanical  regulator,  actuated  by  the 
current  which  maintains  the  secondary  current  of  constant 
strength  and  varies  the  voltage  in  accordance  with  the  number  of 


HANDBOOK    ON    ENGINEERING. 


885 


lamps  in  service.  At  H  another  set  of  transformers  are  used  to 
develop  low  voltage  secondary  currents,  which  pass  through  a 
rotary  converter  /,  and  are  converted  into  a  continuous  current 
to  feed  the  incandescent  lamps  at  J. 

Fig.  402  illustrates  the  arrangement  of  circuits  and  appara- 
tus for  long  distance  transmissions,  which  may  range  all  the 
way  from  five  or  six  miles  up  to  one  hundred  or  more,  the 
greatest  distance  covered  up  to  date  being  145  miles.  To  trans- 
mit current  to  great  distances  with  a  small  loss  in  the  trans- 
mission lines,  it  is  necessary  to  use  very  high  voltages,  ranging 
from  10,000  to  60,000,  and  as  it  is  not  advisable  to  construct 


Fig.  402.    Arrangement  for  long  distances. 

generators  to  develop  such  high  pressures,  raising  transformers 
are  employed  to  develop  the  line  current.  These  transformers  are 
shown  in  Fig.  402  at  A.  The  generator  develops  currents  at  1,000 
volts,  and  this  passing  through  the  primary  coils  of  the  trans- 
formers at  A  induces  secondary  currents  which  may  have  any 
voltage  desired,  say,  20,000.  These  secondary  currents  pass  to 
the  transmission  lines  B  B,  which  may  extend  a  distance  of  ten, 
twenty  or  more  miles  and  may  deliver  all  their  energy  at  the  end 
of  the  line  or  drop  part  of  it  at  intermediate  points.  The  trans- 
formers at  C  and  also  those  at  L  develop  secondary  currents  of 
any  lower  voltage  that  may  be  required  ;  thus,  those  at  C  develop 
secondary  currents  for  the  circuits  7),  which  may  be  of,  say,  1,000 
volts.  The  motor  E  is  shown  connected  directly  with  Z),  but 


886  HANDBOOK    ON    ENGINEERING. 

motor  G  and  lamps  J,  K  require  a  still  lower  voltage,  hence  the 
currents  in  D  are  passed  through  a  second  set  of  transformers  at 
jP,  Hsiud  J.  The  three  transformers  at  L  develop  secondary  cur- 
rents of  sufficiently  low  voltage  to  be  passed  through  the  rotary 
converter  M ,  and  thus  provide  a  continuous  current  for  the  trolley 
road  as  shown. 

STARTING. 

When  the  armature  is  turning,  see  that  the  oil  rings  in  the 
bearings  are  in  motion.  When  the  machine  is  up  to  speed  and  all 
switches  are  open,  lower  the  brushes  on  the  commutator  and  col- 
lector, making  sure  that  each  bears  evenly  and  squarely  on  the 
surface.  Turn  the  rheostat  until  all  resistance  is  in,  then  close 
the  switch  in  the  exciter  circuit.  Set  the  exciter  brushes  properly 
and  adjust  the  voltage  of  the  exciter  to  the  proper  point. 

The  alternator  rheostat  may  then  be  turned  gradually  over  until 
the  proper  alternating  voltage  is  indicated.  The  main  circuit  of 
the  machine  may  now  be  closed.  The  commutator  brushes  should 
be  adjusted  at  a  non-sparking  position.  If  there  is  any  load  the 
voltage  should  increase  slightly.  If  it  decreases,  it  shows  that 
the  series  coils  and  the  separately  excited  coils  are  opposing  each 
other,  unless  this  decrease  is  caused  by  a  drop  in  speed.  If  it  is 
found  that  the  coils  are  opposing  each  other,  unclamp  the  brush- 
holder  yoke  of  the  alternator  and  move  its  commutator  brushes 
backward  or  forward  one  and  one-half  segments  in  a  three-phase 
machine,  and  one  segment  in  a  two-phase  machine.  A  position 
giving  maximum  voltage  will  be  found  from  which  any  motion, 
forward  or  backward,  diminishes  the  voltage.  Having  once  de- 
termined the  correct  setting  of  the  brushes,  they  may  generally 
remain  unchanged,  unless  the  generator  is  subject  to  great  varia- 
tion of  load  when  in  some  machines,  slight  movements  may  be 
found  desirable. 


HANDBOOK   ON   ENGINEERING.  887 

PARALLEL  RUNNING  OF  ALTERNATORS. 

TYPES    SUITABLE    FOR    PARALLEL   OPERATION. 

If  the  speeds  are  exactly  adjusted,  any  two  alternators  of  the 
same  frequency  will  operate  together  in  parallel.  The  maximum 
angular  displacement  that  may  take  place  between  two  machines 
in  parallel  without  causing  objectionable  phase  difference  decreases 
with  increased  number  of  poles.  For  this  reason  high  frequen- 
cies are,  generally  speaking,  less  favorable  to  parallel  operation 
than  lower  frequencies.  Machines  of  the  highest  frequencies 
ordinarily  used  can,  however,  be  successfully  run  in  parallel  if 
the  mechanical  arrangements  are  suitable. 

DIVISION    OF    LOAD. 

Machines  to  operate  in  parallel  must  run  at  such  speeds  as  will 
give  exact  equality  of  frequency.  If  the  prime  mover  running 
one  machine  tends  to  produce  a  lower  frequency  than  that  run- 
ning the  other,  the  machines  cannot  carry  equal  loads. 

When  two  alternators  operate  in  parallel,  each  must  carry  an 
amount  of  load  proportionate  to  the  power  received  from  its  prime 
mover.  If  one  engine  or  water-wheel  governs  in  such  a  manner 
as  to  give  more  power  than  the  other,  this  machine  must  carry  more 
load,  no  matter  what  the  field  excitation  may  be.  If  under  such 
conditions  the  field  excitations  are  correct,  both  machines  will  de- 
liver current  to  the  line  in  approximately  the  proportions  in  which 
they  receive  power  from  their  prime  movers.  If  the  field  adjust- 
ments are  incorrect,  there  will  be  idle  currents  between  the  machines 
in  addition  to  the  currents  which  go  to  the  line. 

COMPOUND    ALTERNATORS. 

When  compound  alternators  are  operated  in  parallel,  equalizer 
connections  should  be  used  so  that  the  rectified  alternating 


888  HANDBOOK    ON    ENGINEERING.. 

current  can  properly  distribute  itself  into  the  fields  of  all  the 
machines.  Without  equalizers,  an  unstable  condition  may  exist 
which  will  render  parallel  operation  unsatisfactory.  This 
applies  particularly  in  the  case  of  machines  driven  from  the 
same  source  of  power.  The  greater  the  amount  of  compounding, 
the  greater  will  be  the  tendency  to  instability. 

BELTED    MACHINES. 

If  two  machines  are  belted  to  separate  prime  movers,  their 
parallel  operation  is  dependent  upon  the  governing  of  the  prime 
movers.  If  they  are  belted  to  the  same  source  of  power,  their 
parallel  operation  depends  upon  the  proportions  of  pulleys  and 
belts,  and  upon  the  tension  and  friction  of  the  latter.  Under 
such  conditions  the  pulleys  and  belts  must  be  adjusted  with  great 
nicety,  so  that  both  machines  will  tend,  with  proper  belt  tension, 
to  run  at  exactly  the  same  frequency.  Even  where  pulleys  are  of 
exactly  the  correct  dimensions,  a  slight  difference  in  the  thick- 
ness of  belts  may  cause  considerable  cross  currents  or  unequal 
division  of  load. 

DIRECT   COUPLED   MACHINES. 

With  such  machines,  engines  must  not  only  be  adjusted  to 
run  at  synchronous  speed,  but  must  also  be  provided  with  fly- 
wheels large  enough  to  prevent  appreciable  variations  of  fre- 
quency within  each  revolution.  Inequalities  of  speed,  due  to 
insufficient  fly-wheel  effect,  will  cause  periodic  cross  currents 
between  dynamos,  or  will  entirely  prevent  their  operation  in 
parallel.  The  greater  the  number  of  poles  in  a  direct  coupled 
machine,  the  less  the  angular  speed  variation  necessary  to  cause 
trouble. 

High  speeds  are  much  more  desirable  with  direct  coupled  alter- 
nators than  low  speeds,  and  low  frequencies  present  less  diffi- 


HANDBOOK   ON   ENGINEERING. 

culties  than  high.  The  desirabilty  of  high  speeds  with  direct 
coupled  alternators  cannot  be  too  strongly  stated.  While  an 
increase  of  fly-wheel  effect  will  equalize  the  angular  irregularities 
of  an  engine's  motion,  it  cannot  bring  about  such  good  results 
as  would  be  brought  about  by  a  similar  reduction  of  angular 
error  effected  through  an  increase  of  speed.  While  the  large  fly- 
wheel steadies  the  motion,  it  may  tend  to  prevent  correction  of 
the  angular  error  through  the  effect  of  the  cross  currents.  Cross 
currents,  which  flow  in  machines  having  light  fly-wheels  may  have 
an  effective  tendency  to  hold  them  together ;  while  machines  with 
very  heavy  fly-wheels  may  tend  to  act  independently  of  each 
other  as  far  as  angular  variations  are  concerned. 

These  matters  should  be  carefully  considered  in  installing 
direct  connected  alternators.  Where  engines  operate  at  the  same 
speed  and  have  the  same  number  of  cranks,  this  trouble  can 
sometimes  be  overcome  by  synchronizing  the  engines  themselves  so 
that  the  impulse  in  both  come  together.  When  the  fly-wheel 
effect  is  insufficient,  the  frequency  will  fluctuate  and  this  fluctua- 
tion may  cause  serious  trouble  if  synchronous  motors  or  rotary 
converters  are  connected  to  the  circuit.  When  the  cranks  of  two 
engines  coupled  to  alternators  are  synchronized,  any  fluctuation  of 
frequency  which  is  due  to  lack  of  fly-wheel  effect  will  still  exist, 
although  it  may  not  affect  parallel  runnkig. 

Where  alternators  have  to  be  operated  in  parallel  by  engines  to 
which  they  are  directly  coupled,  it  is  generally  desirable  to  use 
engines  having  as  many  cranks  as  possible,  so  that  the  crank 
efforts  will  be  well  distributed  throughout  the  revolution,  and 

will  not  tend  to  produce  an  irregularity  of  motion. 

' 

STARTING. 

When  a  machine  driven  by  a  separate  engine  is  thrown  in 
parallel  with  others  which  are  carrying  load,  the  throttle  should 
be  partly  closed  so  that  it  can  just  run  at  synchronous  speed  with- 


890  HANDBOOK   ON    ENGINEERING. 

out  carrying  load.  After  it  is  in  step  with  the  other  machines, 
load  can  gradually  be  taken  on  by  giving  it  more  steam.  If  this 
is  carefully  done  the  voltage  on  the  circuit  is  not  disturbed  by  the 
addition  of  the  new  machine. 

When  a  belted  machine  is  to  be  thrown  into  parallel  with  others 
driven  by  the  same  shaft,  its  belt  tension  should  first  be  reduced, 
which  will  tend  to  admit  enough  slip  to  bring  it  into  step  with 
the  loaded  machines.  After  it  is  thrown  in  it  will  gradually  take 
load  as  the  belt  is  tightened. 

SHUTTING   DOWN. 

In  shutting  down  machines  operating  singly,  both  the  gener- 
ator and  exciter  field  resistance  should  be  cut  in  by  turning  the 
rheostat  before  the  line  switch  is  opened. 

When  two  or  more  generators  are  running  in  parallel  on  the 
bus-bars,  one  may  be  shut  down  at  any  time.  The  equalizer 
switch  should  be  opened  first,  then  the  load  reduced  by  throttling 
the  engine  or  by  slacking  the  belt.  As  soon  as  the  load  is  prac- 
tically off,  open  the  main  switch. 

CAKE    OF    MACHINES. 

With  high  voltage  machines  it  is  absolutely  essential  that  they 
be  kept  scrupulously  clean.  Small  particles  of  copper  or  carbon 
dust,  may  be  sufficient  to  start  a  disastrous  arc. 

The  commutator  collector  should  receive  careful  attention  and 
be  wiped  thoroughly  every  day. 

From  time  to  time  the  machine  should  be  thoroughly  over- 
hauled and  given  a  coating  of  air-drying  japan  after  cleaning. 
Machines  of  the  rotary  field  type  are  so  constructed  that  it  is  a 
comparatively  easy  matter  to  get  at  every  part  of  the  armature 
coils.  In  a  large  station  it  is  recommended  that  an  air  compres- 
sor be  installed  so  that  a  hose  can  be  led  to  the  machine  and  the 
dust  thoroughly  blown  out. 


HANDBOOK   ON    ENGINEERING.  891 

It  is  advisable  to  have  rubber  mats  in  front  of  high  tension 
switchboards  and  on  the  floor  at  the  commutator-collector  end  of 
the  generator.  If  it  is  necessary  to  adjust  the  brushes  while  the 
machine  is  in  operation,  the  attendant  should  stand  on  the  mat 
and  it  is  also  recommended  that  he  wear  rubber  gloves. 

Both  commutator  and  collector  rings  require  a  very  slight 
amount  of  vaseline.  In  applying  it  a  dry  stick  with  a  little 
chamois  leather  tied  to  one  end  may  be  used,  so  that  there  will  be 
no  danger  of  coming  in  contact  with  the  brushes. 

With  the  brushes  properly  set  and  all  screws  firmly  tightened 
into  place,  the  generators  should  require  very  little  attention 
while  running.  It  is  well  to  note  from  time  to  time  whether  the 
oil  rings  are  working  properly. 

Electrical  Formulas. 

Volts  X  Volts 
Watts  =  Amperes  X  Volts.      Watts  = olrnS — 

Watts  ==  Amperes  X  Amperes  X  Ohms. 

Volts 
Volts  —  Amperes  X  Ohms.      Amperes  =  QJ- — 

Volts 

Ohms:=  Amperes  Heat  Units  per  Sec*  =  Amp*  X  AmP-  X  OhmsX  Sees. 
X  0.24 

Watts 
Electrical  Horsepower  =     -,„  » 

TT     "P  N. 

H.  P.  lost  in  conductor  =  16.6538  X  (initial  Volts)  X  length  in  miles. 

2150  X  Watts  per  lamp 
Area  of  cond.  in  circular  mils  =  x  x  %  Qf  drQp  X   no.   of 

lamps  X  dist.  to  center  of  distribution  in  miles,  or 

.    2150  X  dist.  to  center  of  distribution  X  Amperes 
$Tof  Drop  X  Volts 

Distance  in  miles  X  Distance  in  miles 
Weight  of  copper  =  —          — XT  lx 

Volts  X  volts  -5-  100 

100  —  %  of  line  loss  ./  0/»ft  - 
H.  P.del.verec.  to  motor  X    -%  of  „„„  logs 

Energy  Required  to  Produce  1  Candle  Power. 

Watts.                                       Watts.  Watts. 

Tallow 124  Mineral  oils  80       Cannel  gas 48 

Wax 94  Vegetable  oils 57  Incandescent  lamp....    15 

Spermaceti 86  Coal  gas 68       Arc  lamp , 3 


892 


HANDBOOK    ON    ENGINEERING. 


CHAPTER      XXX 


A  CHAPTER  OF  TABLES. 


TABLE  NO.  1.- HYPERBOLIC  LOGARITHMS. 


1 

« 

t* 

3 

0 

I 

It 

3 

o 

tf 

I 

0 

i 

M 

o 

3 

£ 

I 

! 

0 

o 

« 

be 

3 

0 

ti 

5 

1.00 

.0000 

2.45 

.8961 

3  90 

1.3610 

5.35 

.6771 

6  80 

1.9169 

8.25 

2.1102 

9.70 

2.2721 

1.05 

.0488 

2.50 

.9163 

3  95 

1.3737 

5  40 

.6864 

6.85 

9242 

8.30 

2.1163 

9.75 

2.2773 

10 

.0953 

2  55 

.9361 

4  00 

1.3863 

5  45 

.6956 

6.90 

.9315 

8.35 

2  1223 

9  80 

2.2824 

15 

.1398 

2  60 

.9555 

4  05 

1  3987 

5  50 

.7047 

6  95 

.9387 

8  40 

2  1282 

9.85 

2.2875 

.20 

.1823 

2  65 

.9746 

4.10 

1.4110 

5.55 

.7138 

7.00 

.9459 

8.45 

2.1342 

9.90 

2  2925 

25 

.2231 

2  70 

•  9933 

4.15 

1.4231 

5.60 

.7228 

7.05 

.9530 

8.50 

2.1401 

9.95 

2  '2976 

30 

.2624 

2.75 

1.0116 

4  20 

1.4351 

5.65 

.7317 

7.10 

.9601 

8.55 

2  1459 

10.00 

2.30J6 

.35 

.3001 

2.80 

1.0296 

4  25 

.4469 

5  70 

.7405 

7.15 

.9671 

8  60 

2.1518 

.40 

.3365 

2  85 

1.0473 

4.30 

4586 

5.75 

.7402 

7  20 

.9741 

8  65 

2.1576 

.45 

.3716 

2  90 

1  0647 

4  35 

4702 

5.80 

.7579 

7  25 

1.9810 

8.70 

2.1633 

50 

.4055 

2.95 

1.0818 

4  40 

.4816 

5.85 

.7664 

7.30 

1.9879 

8.75 

2.1691 

55 

.4383 

3.00 

1.0986 

4.45 

4929 

5  90 

.7750 

7.3'. 

1.9947 

8.80 

2.1748 

60 

.4700 

3.05 

1.1151 

4  50 

.5041 

5  95 

.7834 

7  40 

2.0015 

8.85 

2.1804 

65 

.5008 

3.10 

1  1314 

4.55 

.5151 

6.00 

7918 

7  45 

2  0082 

8  90 

2.1861 

70 

.5306 

3.15 

1.1474 

4.60 

5261 

605 

8001 

7.50 

2.0149 

8.95 

2.1917 

.75 

.5596 

3  20 

1.1632 

4  65 

.5369 

6.10 

.8083 

7.55 

2.0215 

9.00 

2.1972 

80 

.5878 

3  25 

1.1787 

4.70 

.5476 

6.15 

.8165 

7.60 

2  0281 

9  05 

2.2028 

.85 

.6152 

3.30 

1.1939 

4  75 

.5581 

6.20 

.8245 

7.65 

2.0347 

9.10 

2  2083 

1.90 

.6419 

3.35 

1.2090 

4  80 

.5686 

6.25 

.8326 

7.70 

2.0412 

9.15 

2.2138 

1.95 

.6678 

3.40 

1  2238 

4.85 

5790 

6.30 

.8405 

7.75 

2.0477 

9.20 

2  2192 

2  00 

.6931 

3.45 

1.2384 

4  90 

.5892 

6.35 

.8485 

7.80 

2.0541 

9  25 

2.2246 

2  05 

.7178 

3  50 

1.2528 

4.95 

.6994 

6.40 

.8563 

7  85 

2  0605 

9  30 

2  2300 

2.10 

.7419 

3  55 

1  2669 

5  00 

.6094 

6.45 

.8641 

7.90 

2.0669 

9.35 

2.2354 

2.15 

.7655 

3  60 

1  2809 

5.05 

6194 

6  50 

.8718 

7.95 

2.0732 

9  40 

2.2407 

2.20 

.7885 

3.65 

1  2947 

5.10 

6292 

6.55 

1.8795 

8.00 

2.0794 

9.45 

2.2460 

2.25 

.8109 

3.70 

1  3083 

5  15 

.6390 

6.60 

1.8871 

8.05 

2.0857 

9  50 

2.2513 

2  30 

.8329 

3  75 

1.3218 

5  20 

.6487 

6  65 

1  8946 

8  10 

2  0919 

9.55 

2  2565 

2.35 

.8544 

3  80 

1.3350 

5  25 

.6582 

6  70 

1.9021 

8  15 

2.0980 

9  60 

2.2618 

2.40 

.8755 

3.85 

1.3481 

5.30 

6677 

6  75 

1.9095 

8.20 

2.1041 

9.65 

2.2670 

To  find  the  hyperbolic  logarithm  of  a  ratio  which  is  ten  times  any  ratio  given  in 
the  table,  find  the  ratio  in  the  table  which  is  one-tenth  of  the  giren  ratio  and  add 
2.3026  to  the  corresponding  logarithm;  the  sum  will  be  the  required  logarithm. 
Example:  What  is  the  hyperbolic  logarithm  of  155?  155  is  ten  times  1.55.  The 
logarithm  of  1.55  is  .4383,  and  ,4383  +  2.3026  =* 2.7409  which  is  the  hyperbolic  logar- 
ithm of  16.5. 


HANDBOOK   ON   ENGINEERING. 
TABLE  NO.  2. 


893 


DTJPI/EX    STEAM    PUMPS. 

For  Water  Pressure  Not  Exceeding  150  Ibs.  Speed  from  50  to 
100  feet  per  Minute. 


i 

« 

H 

tf 

JM 

O 

•s!  6 

JsU 

!*rf 

£ 

£ 

2 

c  2  ? 

Jc  ^  c3  Oa" 

.£  u  g>3  a; 

£1 

°2 

•a 

l|s 

1111*3 

•S  Oi  +»  o 

t.s 
e^ 

W    3 

43 

i 

l|§ 

SL-S  J5  o  6 

C  .    4J»  to  CO 

«u 

ctf  PH 

P 

S*fT*!5 

O  C  PH  fe  ^  w 

»j-j    f^jQ  "Jrt    Q 

S 

5 

3 

S    ° 

0< 

0 

3 

2 

3 

.04 

100  to  250 

8  to      20 

4% 

2% 

4 

.10 

100  to  200 

20  to      40 

5% 

3% 

5 

.20 

100  to  200 

40  to      80 

6 

4 

6 

.33 

100  to  150 

70  to    100 

7% 

4% 

6 

.42 

100  to  150 

85  to    125 

7% 

5 

6 

.51 

100  to  150 

100  to    150 

7% 

4% 

10 

.69 

75  to  125 

100  to    170 

9 

10 

.93 

75  to  125 

135  to    230 

10 

6  * 

10 

1.22 

75  to  125 

180  to    300 

10 

7 

10 

1.66 

75  to  125 

245  to    410 

12 

7 

10 

1.66 

75  to  125 

245  to    410 

14 

7 

10 

1.66 

75  to  125 

245  to    410 

12 

8% 

10 

2.45 

75  to  125 

365  to    610 

14 

8% 

10 

2.45, 

75  to  125 

365  to    610 

16 

8% 

10 

2.451 

75  to  125 

365  to    610 

18% 

8% 

10 

2.45 

75  to  125 

365  to    610 

20 

8% 

10 

2.45 

75  to  125 

365  to    610 

12 

flo 

3.57 

75  to  125 

530  to    890 

14 

10%i 

tio 

3.57 

75  to  125 

530  to    890 

16 

10% 

10 

3.57 

75  to  125 

530  to    890 

18% 

10%; 

10 

3.57 

75  to  125 

530  to    890 

20 

10% 

10 

3.57 

75  to  125 

530  to    890 

14 

12 

10 

4.89 

75  to  125 

730  to  1220 

16 

12 

10 

4.89 

75  to  125 

730  to  1220 

18% 

12 

10 

4.89 

75  to  125 

730  to  1220 

20 

12 

10 

4.89 

75  to  125 

730  to  1220 

18% 

14 

10 

6.66 

75  to  125 

990  to  1660 

20 

14 

10 

6.66 

75  to  125 

990  to  1660 

17 

10 

15 

5.10 

50  to  100 

510  to  1020 

20 

12 

15) 

7.34 

50  to  100 

730  to  1460 

20 

fcfc 

15' 

11.47 

50  to  100 

1145  to  2290 

25 

15 

15! 

11.47 

50  to  100 

1145  to  2290 

894 


HANDBOOK    ON    ENGINEERING. 


TABLE  NO.  3 

Tank  or  Light  Service  Pumps. 

These  pumps  are  principally  used  at  railroad  water  stations,  gas  and 
oil  works,  -bleacheries,  tanneries,  refineries,  plantations,  distilleries,  etc.  A 
variety  of  valves  are  used  adapted  for  pumping  hot,  cold,  thick,  thin,  alka- 
line or  other  liquids. 

For  quarries  and  clay  pits,  also  for  coffer  dams,  tunnels,  foundation 
pits,  ore  beds,  sewerage  and  irrigating  purposes,  these  pumps  are.  especially 
adapted,  having  large  water  passages  and  valve  openings.  • 

SIZES  AND  CAPACITIES. 


c 

'    0) 

m 

I 

I 

1 
5.. 

1 
I 

0> 

1. 
Sl 

Capacity  per  minute  at 
ordinary  speed. 

H* 

i 

•& 

£ 

fs 

aj 

i 

*s»  • 
§3 

ery  pipe, 
bes. 

Floor  Space 
Required. 
Inches. 

8*0 

0)   O 

X 

o  g 

03  o 

ts  13 

>  o 

P 

I* 

1 

3S 

• 

A  a 

o  a 
cJ 

is 

GO 

£ 

03 

O 

00 

fir" 

CO 

Q 

""Ik 

3& 

4 

.15 

125  Strokes,   .18  gals. 

4. 

* 

14 

154 

28    xlO 

4 

4 

5 

.27 

125                    33 

4 

X 

2 

14 

34    xll 

5 

4 

7 

.39 

125        ••            49 

K 

24 

2 

44    x!2 

54 

54 

7 

.72 

125        "           90 

B 

3 

24 

44    xl34 

6 

f>% 

7 

.72 

125        "            90 

i 

3 

24 

44    x'134 

6 

6 

12 

1.47 

100        ••          147 

i 

4 

4 

66^x19  ' 

6 

7 

12 

2.00 

100        "          200 

x 

5 

5 

662£xl9 

74 

7 

10 

1.66 

100        ••          166 

54 

5 

5 

56J4xiy 

74 

74 

10 

1.91 

100        "          191 

34 

5 

5 

564x19 

8 

6 

12 

1.47 

100        "          147 

iff 

4 

4 

66^x19 

8 

7 

12 

2.00 

100        •'          200 

134 

5 

5 

665^x19 

8 

8 

12 

2.61 

100       "          261 

1J4 

5 

5 

662ix20 

8 

9 

12 

3,30 

100        "          330 

tM 

6 

6 

66^x214 

8 

10 

12 

4.08 

100        »•         (408 

154 

6 

6 

66^x214 

10 

10 

12 

4.08 

100        "         408 

15< 

14 

6 

6 

66^x214 

10 

10 

16 

5.44 

75        "          408 

1J4 

14 

6 

6 

78^x21>/3 

10 

12 

12 

5.87 

100        "          587 

1M 

14 

8 

•6 

66%x23>4 

10 

12 

16 

7.83 

75        "          587 

134 

8 

6 

78/8x23'4 

12 

10 

12 

4.08 

100        "          408 

2 

gi/ 

6 

6 

66^x214 

12 

10 

16 

5.44 

75        "          408 

2 

24 

6 

6 

78^x214 

12 

12 

12 

5.87 

100.        •          587 

2 

24 

8 

6 

66^x23^ 

12 

19 

16 

7.83 

75         '          587 

2 

24 

8 

6 

784x23«£ 

14 

12 

12 

5.87 

100         '          587 

2 

24 

8 

6 

(56^x235^ 

14 

12 

16 

7.83 

'75         <          587 

2 

24 

8 

6 

784x23^ 

14 

14 

16 

10.66 

75'        '•         -800 

2 

24 

10 

8 

784x27 

14 

14 

24 

16.00 

£0         *,         800 

24 

3 

10 

8 

108    x27 

14 

16 

16 

14.92 

75.        '        1020 

24 

3 

12 

10 

80    x354 

14 

16 

24 

20.88 

50,        '        1044 

24 

3 

12 

10 

108    X35J4 

16 

14 

16 

10.66 

75         •          800 

24 

3 

10 

8 

784x27 

16 

14 

24 

16.00 

60         '          800 

24 

3 

10 

8 

108    x27 

16 

16 

16 

14.92 

75         '        1020 

24 

3 

12 

10 

80    x354 

16 

16 

24 

20.88 

50        "        1044 

24 

3 

12 

10 

108    x354 

16 

18 

24 

26.44 

50        ••        1322 

24 

3 

12 

10 

108    x38 

16 

20 

24 

32.64 

50        "        1632 

24 

3 

14 

12 

108    x40 

18 

16 

24 

20.88 

50       "         1044 

34 

4 

12 

10 

110    x354 

18 

18 

24 

26.44 

50         <        1322 

34 

12 

10 

110    x38 

18 

20 

24 

32.61 

50         '        1632 

34 

14 

12 

110    x40 

18 

22 

24 

39.50 

50         '        1975 

34 

14 

14 

110    x42 

20 

18 

24 

26.44 

50         '        1322 

34 

12 

10 

118    x38 

20 

20 

24 

32.64 

50         '        1622 

34 

14 

12 

118    X40 

20 

22 

24 

39.50 

60         '        1975 

34 

14 

14 

118    x42 

20 

24 

24 

47.00 

60         •        2350     • 

q* 

4 

16 

16 

118     £44 

HANDBOOK    ON    ENGINEERING. 


895 


TABLE  NO.  4. 


DIAMETERS,  AREAS  AND  CIRCUMFERENCES 
OF  CIRCLES. 


•w 

4 

'  d 

|s 

I 

c"3' 

f«5 

•d 

§fl 

3X3 

a>M 

§J3 

t< 

5« 

*s 

s§ 

•o5 

$ 

«S 

5* 

<$ 

«s 

.b  a 

1 

3.14159 

'0.78540 

4 

12.5664 

12.566 

8 

25.1327 

50.265 

A 

3.33794 

0.88064 

i 

12.7627 

12.962 

H 

25  5224 

51.84.9 

8 

3.53429 

0.99402 

^8 

12.9591 

13.364 

25.9181 

53.456 

1 

3.73064 
3.92699 

1.1075 
1.2272 

ft 

13.1554 
13.3518 

13.772 
14.186 

$ 

26.3108 
26.7035 

55.088 
56.745 

4.12334 

1.3530 

A 

13.5481 

14.607 

% 

27.0962 

58.426 

rt 

4.31969 

1.4*49 

\l 

13.7445 

15.033 

% 

27.4889 

60.133 

/a 

4.51604 

1.6230 

13..  9408 

15.466 

% 

27.8816 

61.862 

fc 

4.71239 

1.7671 

H 

14.1372 

15.904 

9 

28.2743 

63.617 

i9<f 

4.90874 

1.9175 

14.3335 

16.349 

H 

28.6670 

65.397 

£l 

5.10509 

2.0739 

/8 

14.5299 

KU'OO 

H 

29.0597 

67.201 

ri 

5.30144 

2.2365 

11 

14.7262 

17.257 

96 

29.4524 

69.029 

5.49779 

2.4053 

% 

14.9226 

17.721 

J£ 

29.8451 

70.882 

13 

5.69414 

2.5802 

13 

15.1189 

18.190 

% 

30,2378 

'72.760 

% 

5.89049 

2.7612 

/8 

15.3153 

18.665 

'£ 

30.6305 

74.662 

h 

6.08684 

2.9483 

i1  3 

15.5116 

19.147 

31.0232 

76.589 

2 

6.28319 

3.1416 

r> 

15.7080 

19.635 

10 

31.4159 

78.540 

>\j 

6.47953 

3.3410 

15.9043 

20.129 

32.2013 

82.516 

M 

6.67588 

3.5466 

/Q 

16.1007 

20.629 

l/2 

32.9867 

86.690 

6.87223 

3.7583 

1\ 

16.2970 

21.135 

%    - 

33.7721 

90.763 

5* 

7.06858 

3.9761 

y± 

16.4934 

21.4348 

11 

34.5575 

95.033 

5 

7.26493 

4.2000 

8 

10.0897 

22.166 

35.3429 

99.402 

% 

7.46128 

4.4301 

% 

10.8861 

22.691 

H 

36.1283 

103.87 

I7* 

7.65763 

4.6664 

I7H 

17.0824 

23.221 

X 

30.9137 

108.43 

H 

7.85398 

4,9087 

54 

17.2788 

23.758 

12 

37.6991 

113.10 

8.05033 

5.1572 

*& 

17.4751 

24.301 

14 

38.4845 

117.86. 

ft 

8.24668 

5.4119 

% 

17.6715 

24.850 

r| 

39.2699 

122.72 

ti 

8.44303 

5.0727 

n 

17.8678 

25,406 

5^ 

40.0553 

127.68 

3^ 

8.63938 

5.9390 

% 

18.0642 

25.967 

13 

40.840> 

132.73  v 

jn 

8.83573 

6.2126 

li 

18.2605 

20.535 

41.6261 

137.89 

« 

9.03208 

0.4918 

% 

18.4569 

27.109 

16 

42.4115 

143.14 

II 

0.22843 

6.7771 

IS 

18.6532 

27.688 

k 

43.1969 

148.49 

3^ 

9.42418 

7.06S6 

6 

18.8496 

28.274 

14 

43.9823 

153.94 

11.62115) 

7.3662 

Vs 

19.2423 

29.465 

H 

44.767r 

159.48 

•8 

9.81748 

7.6699 

14 

19.6350 

30.680 

45.5531 

165.13 

ino 

10.0138 

7.9798 

H 

20.0277 

31.919 

% 

46.3385 

170.87 

l'\ 

10.2102 

8.2958 

Yz 

20.4204 

33.183 

15 

47.1239 

176.71, 

J5fl 

10.4065 

8.6179 

20.8131 

34.472 

47.9093 

182.65. 

U£ 

10.^029 

8.9462 

% 

21.2058 

35.785 

Vz 

48.694" 

188.69 

l'7rt 

10.7992 

9.2800 

ft 

21.5984 

37.122 

% 

49.4801 

194.83. 

i^ 

10.9950 

9.0211 

7 

21.9911 

38.485 

16 

50.2655 

201.061 

jjjj 

11.1919 

9.9678 

22.3838 

39.871 

|4 

51.0509 

207.  39V 

11.3S83 

10.321 

^ 

22.7765 

41.282 

51.8363 

213.82- 

io 

1L5846 

10.080 

?» 

23.1692 

42.718 

% 

52.621" 

220.35 

3a 

11.7810 

11.045 

Va 

23.5619 

44.179 

17 

53.4071 

226.98- 

3 

11.977;.' 

11.418 

?8 

23.9546 

45.664 

W 

54.192: 

233.  7t 

x 

12.1737 

11.793 

3/ 

24.3473 

47.173 

ll 

54.9779 

24o  53 

is 

12.3700 

12.177 

3 

24.7400 

4S.707 

05.7030 

247.  4&. 

896 


HANDBOOK   ON   ENGINEERING. 


Diameters,  Areas  and  Circumferences  of  Circles.— Con. 


Diam.  II 
Inches. 

Circumf. 
Inches. 

s 

Diam. 
Inches. 

Circumf. 
Inches. 

gs 

l| 

Circumf. 
Inches. 

fi 

18 

56.5487 

254.47 

32 

100.531 

804.25 

46 

144.513 

1661.0 

54 

57.3341 

2t<1.59 

54 

101.316 

816.86 

H 

145.299 

1680.0 

58.1195 

268  80 

3 

102.102 

829.58 

B 

146.0.S4 

1698.2 

3£ 

68.9049 

276.12 

1H2.887 

842.39 

146.869 

716.5 

19 

59.6903 

283.53 

33* 

103.673 

855.30 

47'4 

147.65;-. 

734.9 

54 

60.4757 

291.04 

104.458 

fc'68.31 

54 

148.440 

753.5 

H 

61.2611 

2-J8.65 

Vi 

105.243 

881.41 

149.226 

772.  J 

62.0465 

306.35 

% 

106.029 

894.62 

94 

150.011 

75>0.8 

20 

62.8319 

314.16 

34 

106.814 

907.92 

48 

150.796 

1809  6 

54 

63.6173 

3^2.06 

54 

107.600 

921.32 

H 

151.582 

1828.5 

H 

64.4026 

330.00 

H 

108.385 

934.82 

152.367 

1847.5 

66.1880 

338.16 

109.170 

•948.42 

3 

153.  15H 

1866.5 

21  * 

65.9734 

346.36 

354 

109.956 

962.11 

49 

133.938 

1885.7 

54 

66.7588 

354.66 

54 

110.741 

975.91 

154.723 

1905.0 

V* 

67.5442 

363.05 

H 

111.  627 

989.80 

y 

155.509 

1924.2 

68.329H 

371.54 

112.312 

1003.8 

& 

156.294 

1943.9 

224 

69.1150 

380.13 

36  4 

113.097 

1017.9 

50 

157.080 

1963.5 

54 

69.9004 

388.82 

54 

113.883 

1032.1 

54 

157.865 

1983.2 

H 

70.6858 

397.61 

% 

114.668 

1046.3 

K 

158.650 

2003.0 

71  4712 

406.49 

115.454 

J060.7 

159.436 

2022.8 

23 

72.2566 

415.48 

37  4 

116,239 

1075.2 

51  4 

160.221 

2042.8 

54 

73  .'0420 

424.56 

54 

117.024 

1089.8 

161.007 

2062.9 

y* 

73.8274 

433.74 

H 

117.810 

1104.5 

H 

161.792 

2083.1 

% 

74.6128 

443.01 

118.596 

1119.2 

162.577 

2103.3 

24 

75.3982 

452.39 

384 

119.381 

1134.1 

52/4 

163.363 

2123.7 

5-4 

76.1836 

461.86 

H 

120.166 

1149.1 

M 

164.148 

2144.2 

H 

76.9690 

471.44 

H 

120.951 

1164.2 

H 

164.934 

2164.8 

* 

77.7544 

481.11 

121.737 

1179.3 

165.719 

2185.4 

25 

78.5398 

490.87 

39  4 

122.522 

1194.6 

534 

166.504 

2206.2 

54 

79.3252 

500.74 

123.308 

1210.0 

54 

167.290 

2227.0 

n 

80.1106 

510.71 

Vi 

124.093 

1225.4 

168.075 

2248.0 

% 

80.8960 

520.77 

94 

124.878 

1241.0 

94 

168.861 

2269.1 

20 

81.6814 

530.93 

40 

125.664 

1256.6 

54 

169.646 

2290.3 

54 

82.4668 

541.19 

K 

126.449 

1272.4 

54 

170.431 

2311.5 

K 

83.2522 

551.55 

127.235 

1288.2 

171.217 

2332.  » 

84.0376 

562.00 

9£ 

128.020 

1304.2 

94 

172.002 

2354.3 

27* 

84.8230 

572.56 

41 

128.805 

1320.3 

55^ 

172.788 

2375.8 

54 

85.6084 

583.21 

54 

129.591 

1336.4 

173.573 

2397.5 

86.3938 

593.96 

130.376 

1352.7 

y 

174.358 

2419.2 

9s£ 

87,1792 

604.81 

94 

131.161 

1369.0 

% 

175.144 

2441.1 

~H 

87.9646 

615.75 

42 

131.947 

1385.4 

56 

175.929 

2463.0 

54 

88.7500 

626.80 

54 

132.  732 

1402.0 

176.715 

2485.0 

H 

89.5354 
90.3208 

637,94 
649.18 

y* 

133.518 
134,303 

1418.6 
1435.4 

& 

177.500 

178.285 

2507.2 
2529.4 

so'4  . 

91.1062 

660.52 

434 

135,088 

1452.2 

57 

179.071 

2551.8 

54' 

91.8916 

671.  9d 

54 

1469.1 

179.856 

2574.2 

'/a 

92.67-50 

683.49 

Vi 

136  1659 

1486.2 

H 

180.642 

2596.7 

?£ 

93.4624 

695.13 

137.445 

1503.3 

9i 

181  .427 

2619.4 

BO 

94.2478 

706.86 

44* 

138.230 

1520,5 

58 

182.212 

XJ642.1 

H 

95.0332 

718.69 

54 

139.015 

1537.9 

182.998 

2664.9 

H 

95.8186 

730.62 

/4 

139.801 

1555.3 

y 

183.783 

2687.8 

*j 

96.6040 

742.64 

a' 

110.586 

1572.8 

%t 

184.569 

2710.9 

81 

97.3894 

754.77 

45' 

141.372 

1590.4 

59 

185.ar>4 

2734.0 

fe 

98.  1748 

766.  9j) 

54 

142.157 

1608.2 

186.139 

2757.2 

H 

98.9602 

779.31 

H 

142.942 

1626.0 

y 

186.925 

2780.5 

~*» 

99.7456 

791.73 

143.728 

1643.0 

% 

187.710 

2803.9 

HANDBOOK   ON    ENGINEERING. 


897 


Diameters,  Areas  and  Circumferences  of  Circles. — Con. 


Diam.  !| 
Inches.. 

Circumf. 
Inches. 

SM 

% 

Diam. 
Inches. 

Circumf, 

Inches. 

f 
*& 

Diam. 
Inches. 

Circumf. 
Inches. 

II 

.60 

188.496 

2827.4 

74 

232.478 

4300.8 

88 

276.460 

6082.1 

189.281 

2851.0 

h 

233.263 

4329.9 

k 

277.246 

6116.7 

y* 

190.066 

2874.8 

l/2 

234.049 

4359.2 

i? 

278.031 

6151.4 

% 

190.852 

2898.6 

% 

334.834 

4388.5 

H 

278.816 

6186.2 

61 

191.637 

2922.5 

75 

235.619 

4417.9 

,89 

279.602 

6221.1 

'  J4 

192.423 

2946/5 

& 

236.405 

4447.4 

H 

2«0.387 

6256.1 

5? 

193'.  208 

2970.6 

Yz 

237.190 

4477.0 

l/2 

281.173 

6291.2 

% 

193.993 

2994.8 

% 

237.976 

4506.7 

u 

281.958 

6:£H'.4 

62 

194.779 

3019.1 

76 

^38.761 

4536.5 

901/ 

282.743 

6361.7 

& 

195.564 

8048.5 

!/4 

239.546 

4566.4 

283.529 

6397.1 

H 

196.350 

3068.0 

tt 

2i0.332 

4596.3 

H 

284.314 

6432.6 

% 

197.135 

3092.6 

% 

241.117 

4626.4 

'  % 

285.100 

6468.2 

63 

197.920 

3117.2 

77 

241.903 

4656.6 

91 

285.885 

6503.9 

1A 

198.706 

3142.0 

& 

242.688 

4086.9 

H 

286.670 

6539.7 

4 

199.491 

3166.9 

H 

243.473 

4717.3 

M 

287.456 

6575  5 

% 

200.277 

3191.9 

* 

244.259 

4747.8 

% 

238.241 

6611.5 

64 

201.062 

3217.0 

78 

245.044 

4778.4 

$2 

289.027 

66-17.6 

H 

201.847 

3242.2 

K 

245.830 

4809.0 

K 

289.812 

(5683.8 

H 

202.633 

3267.5 

H 

246.615 

4839.8 

•   l/2 

390.597 

6720.1 

% 

203.418 

3292.8 

it 

247.400 

4870.7 

% 

291.383 

6756.4 

66 

204.204 

3318.3 

79 

248.186 

4901.7 

88 

202.168 

6792.9 

/4 

204.989 

3343.9 

K 

248.971 

4932.7 

H 

292.954 

6829.5 

y$ 

205.774 

3369.6 

% 

249.757 

4963.9 

'/2 

293.739 

6866.1 

% 

206.560 

3395.3 

% 

250.542 

4995.2 

•  % 

294.524 

6902.9 

66 

207.345 

3421.2 

80 

251.327 

5026.5 

9;4 

295.310 

6939.8 

34 

208.131 

3447.2 

k 

252.113 

5058.0 

r?H 

296.095 

6976.7 

H 

208.916 

3473.2 

* 

252.898 

5089.6 

'/2 

296.881 

7013.8 

V 

209.701 

3199.4 

% 

253.684 

5121.2 

'% 

297.666 

7051.0 

67 

210.487 

3525.7 

81 

254.469 

5153.0 

95 

398.451 

7088.2 

fc 

211.272 

3552.0 

y* 

255.254 

5184.9 

'H 

399.237 

7125.6 

l/2 

-412.058 

3578.5 

K 

256.040 

5216.8 

'   l/2 

300.022 

7163.0 

% 

212.843 

3605.0 

x 

256.825 

5248.9 

^  % 

300.807 

7200.6 

68 

213.628 

3631.7 

82 

257.611 

5281.0 

96 

301.593 

7238.2 

K 

214.414 

3658.4 

y\ 

258.396 

5313.3 

H 

302.378 

7276.0 

3 

215.199 

3685.3 

y* 

259.181 

6345.6 

3 

303.164 

7313.8 

% 

215.984 

3712.2 

%• 

359.967 

5378.1 

1i 

303.949 

7351.8 

«9 

216.770 

3739.3 

83 

260.752 

5410.6 

97 

304.734 

7389.8 

14 

217.555 

3766.4 

y± 

261.538 

5443.3 

M 

305.520 

742S-.0 

y* 

218.341 

3793.7 

1A 

262.323 

5476.0 

v  H 

306.305 

7466.2 

u 

219.126 

3821.0 

% 

263.108 

5508.8 

•  % 

307.091 

7504.5 

70 

219.911 

3848.5 

84 

263.394 

5541.8 

98 

307.876 

7543.0 

tt 

220.697 

3876.0 

\i 

264.679 

5574.8 

H 

308.661 

7581.5 

l/i 

221.482 

3903.6 

H 

265.465 

5607.9 

y* 

309.447 

7620.1 

94" 

222.268 

3931.4 

3^ 

266.250 

5641.2 

% 

310.232 

7658.9 

71 

223.053 

3959.2 

55 

267.035 

5674.5 

"i 

311.018 

7697.7 

H 

223.838 

3987.1 

!/i 

267.821 

5707.9 

311.803 

7736.6 

3 

224.624 

4015.2 

H 

268.606 

5741.5 

H 

312.588 

7775.6 

% 

225.409 

4043.3 

^ 

269.392 

5775.1 

% 

313.374 

7814.8 

72 

226.195 

4011.5 

86 

270.177 

5808.8 

100 

314.159 

7854.0 

H 

226.980 

4099.8 

H 

270.962 

5842.6 

Vi 

227.765 

4128.2 

% 

271.748 

5876.5 

% 

228.551 

4156.  8 

% 

272.533 

5910.6 

-73 

229.336 

4185.4 

87 

273.319 

5944.7 

230.122 

4214.1 

H 

274.104 

5978.9 

H 

230.907 

4242.9 

3 

274.889 

6013.2 

3rf 

281.^2 

4271.8 

y 

2T6.R75 

6017.0 

898 


HANDBOOK    ON    ENGINEERING. 


TABLE  NO.  5. 

CUBIC  FEET  OF  AMMONIA  GAS  "PER  MINUTE  TO 
PRODUCE  ONE^TON  OF  REFRIGERATION  PER  DAY. 

CONDENSER. 


P 

P 

103 

"5 

127 

139 

153 

168     185 

200 

218 

t  ;  65° 

70° 

75° 

80° 

85° 

90°j    '95° 

100 

105° 

* 

r      A    2O° 

7   I         o 

5.84 

5-9 

5.96 

6.03 

6.06 

6.16 

6.23 

6.30 

6.43 

o 

0 

^o: 

5.35 

5-4 

5.46 

5-52 

5.58 

5-64 

5.70 

5-77 

h 

9 

—  10    j 

4.66 

4-73 

4.76 

4.81 

4.86 

4.91 

4-97 

5-°5 

5-oS 

w 

13 

~"   0 

4.09 

4.12 

4.17 

4.21 

4.25 

4.3° 

4-35 

4.40 

4.44 

o 

16 

°   \ 

3.59 

3-63 

3-66 

3-70 

3-74 

3.78 

3.83 

3.87 

2 

20 

5  \ 

3-2C 

3.24 

3-27 

3.30 

3-34 

3.38 

3-41 

3.45 

3-49 

w 

Jo 

10° 

2.87 

2.9 

2-93 

2.96 

2.99 

3.02 

3.06 

3-°9 

3.12 

28 

'5 

2.59 

261 

2.65 

2.68 

2.71 

2-73 

2.76 

2.80 

2.82 

!. 
aj 

20 

2.31 

2-34 

2.36 

2.38 

2.41 

2-44 

2.46 

2.49 

2.51 

39 

25* 

2.06 

2.08 

2.10 

2.12 

2.»  5 

2.17 

2.  2O 

2.  -2  2 

2.24 

« 

3° 

1.85 

1.87 

1.89 

I.9I 

1-93 

1.95 

1.97 

2.00 

2.OI 

3i> 

1.70 

1.72 

1.74 

1.76 

1.77 

1.79 

1.81 

1.83 

1.85 

TABLE  KG.  6. 

PROPERTIES  OF  SULPHUR  DIOXIDE. 


t 

.  P 

H 

h 

L 

V 

\\ 

V 

.  22 

T"1* 
—4 

S.S^ 
7-23 
9.27 

157.43 
158.64 
159.84 

^19-56 
—16.30 

—  »3-°5 

176.99 

•174.95 
172.89 

I3.I7 
10.27 

8.12 

.076 
.097 
.123 

.4041 
.3914 
•3791 

5 
«4 

23 

11.76 
14.74 
18.31 

161.03 
162.20 
163.66 

—9.79 
-6.53 
—3.27 

170.82 
168.73 
166.63 

6.50 

5.25 
4.29 

•153 
.190 
.232 

•3673 
•3559 
•3449 

32 
4< 

5° 

«.53 
27.48 

33-25 

164.51 
165.65 
166.78 

o.oo 

3-27 

6.55 

164.5  r 
162.38 
160.23 

3.54 
2.93 

2.45 

.282 
•340 
.406 

•3344 
.3241 
.3M2 

59 

68 

77 

39  33 
47-61 

56.39 

167.90 
168.99 
170.09 

9.83 
13." 
16.39 

158.07 
155-89 
153-7° 

2.07 

i-75 
1.49 

•483 
•570 
.669 

.3046 
.2952 
.2861 

86 

95 
104 

66.36 
77.64 
90.31 

171.17 
172.54 
1  73.30 

19.69 
22.98 
26.28 

15L49 
149.26 
147.02 

1.27 
1.09 
.91 

.780 
.906 
1.046 

.2774 
.2689 
.2607 

HANDBOOK    ON    ENGINEERING. 


899 


TABLE  NO.  7. 

PROPERTIES  OF  AMMONIA. 


t 

*4 

A. 

B 

t 

*=4 

A 

B 

—40 

1.3802 

.0000 

.0000 

60 

•9959 

.2136 

.1707 

—  35 

1.3569 

.0118 

.0115 

65 

.9803 

.2231 

.1768 

1-3343 

.0236 

.0224 

70 

.9651 

.2326 

.1825 

—  25 

1.3119 

.0351 

.0332 

75 

.9500 

.2420 

.1881 

—20 

1.2902 

.0465 

.0435 

80 

•9353 

•2513 

•1936 

—15 

1.2689 

.0578 

•0535 

85 

.9207 

.2605 

.1990 

—  10 

1.2481 

.0690 

.0631 

90 

.9065 

.2696 

.2042 

—  5 

1.2276 

.0800 

.0726 

95 

.8922 

.2787 

.2093 

*  0 

1.2076 

.0910 

.0816 

100 

.8788 

.2877 

.2140 

+5 

1.  1880 

.1018 

.0904 

105 

.8650 

.2966 

.2186 

10 

1.1688 

.1125 

.0989 

no 

.8516 

•3054 

.2232 

15 

1.1500 

.1230 

.1072 

115 

•8385 

.2276 

20- 

1.1315 

•  1335 

.1152 

120 

.8255   .3228 

-2319 

1.1134 

.1439 

,1229 

125 

.8129 

•33i3 

.2360 

30 

1.0957 

.1541 

.1304 

130 

.8002 

.3398 

.2402 

35 

1.0783 

.1643 

.1376 

US 

.7878 

•3483 

.2441 

40 

1.0613 

.1743 

.1446 

140 

•7756 

•3567 

.2479- 

45 

1-0445 

.1843 

.1514 

145 

.7636 

•3650 

.2516 

5° 

1.0280 

.1941 

.1581 

150 

.7518 

•3732 

•255* 

55 

1.0118 

.2039 

.1645 

,7402 

.3814 

.2586 

—  logeli. 


In  this  table  : 

AA  —  A  2  =  c  loge  lj  ;  where  c  is  the  specific  heat  of 
liquid  ammonia,  c  is  assumed  equal  to  1;  if  any  other 
value  is  taken  the  numbers  in  the  table  must  be  multiplied 
by  that  value.. 

^-63  =  9s  - 

Examples  of  use  of  table  : 

(1)  Per  cent,  of  liquid  in  wet  compression  to  prevent 
superheating  =  (Bj-B2)/^2. 

(2)  Superheating  above  condenser  with  dry  compres-. 
sion  =  ,0a,(7Bi7BB;lTB^ 

(3)  Work  to  compress,  i  pound  of  ammonia  =  788 
(T\  -  T2)  9>2  ;—  i  cubic  foot  =  788  (T,  —  T2)  <P2  W8. 

(4)  Mean  pressure  =  «f  (T,  -  T2)  <P2  W2. 

(5)  Equation  of  adiabatic  A9  +  «3^2  =  Al  +  »,9r 


900 


HANDBOOK    ON    ENGINEERING. 


TABLE  NO.  8. 

PROPERTIES  OF  CARBONIC  ACID. 


f   | 

P 

H 

h     L 

v 

w 

0 

i 

_  .- 

_  



. 

—     , 

.  , 

—  22 

210 

98.35 

—37.80    136.15 

.4138 

!  2.321  « 

.3108 

—  13 

249 

99.14 

—32.51 

131.65 

•3459 

j  2:759 

.2945 

—  4 

292 

99.88 

26.91    126.79 

.2901 

3-265 

.2785 

1 

j 

5  ; 

342    100.58 

^—20.92 

121.50 

.2438 

1  3.853 

.2613 

14 

396 

IOI.2I 

—  14.49  I!5-7° 

.2042 

,  4.535 

.2441 

23 

457 

IOI.8I 

—7.56  '  109.37 

.1711 

!'   5.331 

I 

.2262 

32 

525 

102.35 

o.oo 

102.35 

.1426 

•:  6.265 

*•  .2080 

41 

599 

IO2.84 

8.32 

94-52 

.1177 

7-374 

.1887 

5° 

680 

103.24 

17  60   85.64 

.0960 

'  8.708 

•'679, 

i 

1 

59 

768 

103.59 

28.22 

75-37 

.0763 

i  10.356 

.1452 

68 

864  j  103.84 

40.86 

62.98 

•0577 

j  12.480 

77 

968 

10395 

57.06   46.89 

.0391 

:i5475 

.0873 

86 

1.080 

10372 

84.44  '  19-28 

.0147 

21.519 

.0353 

1         i 

TABLE  NO.  9. 

PROPERTIES  OF  BRINE  SOLUTIO'N. 
(Common  Salt.) 


1 

•ifc 

Wo 

!- 

i 

1. 
[1 

i 

ific  Gravity 
it  60°  F. 

1 

:ific  heat. 

I  . 

11 

i 

li 

^"3, 

"?  e 

1 

f 

I* 

F 

1 
* 

I 

I 

So 
& 

r 

^ 

o 

0 

0 

X. 

i. 

8.35 

0. 

62.4 

32. 

I 

r-4 

i 

1.007 

0.992 

8-4 

0.084 

62.8 

5 

;  [20 

5 

-037 

0.96 

8.65 

0.432 

64.7 

25.4 

10 

40 

10 

.073 

0.892 

8-95 

0.895 

66.95 

18.6 

15 

60 

15 

.H5 

0-855 

9-3 

1-395 

69.57 

12.2 

20 

80 

'9 

0,829 

9-6 

1.92 

71.76 

6.86 

35 

IOO 

23 

.191 

0.783 

9-94 

2.485 

74,26 

1.00 

HANDBOOK   ON   ENGINEERING. 


901 


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a^nssa^a 


902 


HANDBOOK   ON   ENGINEERING. 


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HANDBOOK   ON   ENGINEERING. 


903 


TABLE  NO.  12. 

Reaumufj  Fahrenheit,  and  Celsius 
Thermometers  Compared. 


R. 

F. 

C. 

-Hnn 

E-+210-E 

75-- 

E-  205-E 

E-  200-E 

--95 

E4-  195-E 

--90 

70-- 
65-- 

E-  190-E 

—            — 

j  o  er 

Q  tf 

•~       155 

- 

E-  iso-E 

E-  175-E 

55 
--80 

60-- 

E-  170-  E: 

E-  165-E 

75 

55-- 
50-- 
45-- 

E-  160-E 

E-  155-E 
:-  150-  = 

:-70 

E-  145-  E 

R  A 

:      140-  _ 
E-  135-E 

e;  K 

--  13Q-: 

40-- 
35-- 

E-  125-E 

-           j  o  A 

:-«» 

E-  U5-E 

y|  •£ 

E-  uo-E 

----- 

32l 

1-105-1 

1-40 

R 

R 

C. 

+32-  - 
30-- 

-+104    i 

—  loo-E 

-  35 

--30 

25-- 

E—  90~E 
E—  85-E 

20-- 

E-  so-E 

--25 

15-- 

E—  TO  -E 

_    OA 

E  —  65  -E 

E-  eo-E 

--  15 

10-- 
5-- 

E—  55-E 

J  A 

:        50      r 

— 

:_  4Q-E 

--  5 

o-- 

E—  35-E 
E-  30-E 

--  0 

-5-- 

E—  25-  E 

E-.20-E 

-—  5 

E—  15-E 

—  10 

10-- 
15- 

E-  IO-E 

—    4R 

- 

:-    0- 

_ 

904 


HANDBOOK   ON   ENGINEERING. 


3. 


O 
to 

H 

PQ 

a 


•JN3JL 


905 


HANDBOOK    ON    ENGINEERING. 

TABLE  NO.  14. 

Weight  of  Rivets   and  Round  Headed  Bolts  Without 

Per  100. 

LENGTH  FROM  UNDER   HEAD.     ONE  CUBIC  FOOT  WEIGHING  480  LBS^ 


LENGTH 
INCHES. 

3/8" 
DIAM. 

y2" 

DIAM. 

%" 

DIAM. 

w 

DIAM. 

%" 
DIAM. 

1" 

DIAM. 

I'/s" 

DIAM. 

1U" 

DIAM. 

U4 

5.4 

12.6 

21.5 

28.7 

43.1 

65.3 

91.5 

123. 

1% 

6.2 

13.9 

23.7 

31.8 

47.3 

707 

98.4 

133. 

i% 

6.9 

15.3 

25.8 

34.9 

51.4 

76.2 

105. 

142. 

2 

7.7 

16.6 

27.9 

37.9 

55.6 

81.6 

112. 

150. 

2*4 

8.5 

18.0 

30.0 

41.0 

59.8 

87.1 

119. 

159. 

2Y2 

9.2 

19.4 

32.2 

44.1 

63.0 

92.5 

126. 

167. 

23^ 

10.0 

20.7 

34.3 

47.1 

68.1 

98.0 

133. 

176. 

3 

10.8 

22.1 

36,4 

50.2 

72.3 

103. 

140. 

184. 

3^4 

11.5 

23.5 

38.6 

53.3 

76.5 

109. 

147. 

193. 

3V3 

12.3 

24.8 

40.7 

56.4 

80.7 

114. 

154. 

201. 

3% 

13.1 

26.2 

42.8 

59.4 

84.8 

120. 

161. 

210. 

4 

13.8 

27.5 

45.0 

62.5 

89.0 

125. 

167. 

218, 

4H 

14.6 

28.9 

47.1 

65.6 

93.2 

131. 

174. 

227. 

4V2 

15.4 

30.3 

49.2 

68.6 

97.4 

136. 

181. 

236. 

43/4 

16.2 

31.6 

51.4 

71.7 

102. 

142. 

188. 

244. 

5 

16.9 

33.0 

53.5 

74.8 

106. 

147. 

195. 

253. 

6H 

17.7 

34.4 

55.6 

77.8 

110. 

153. 

202. 

261. 

5V2 

18.4 

35.7 

57.7 

80.9 

114.. 

158.- 

209. 

270. 

534 

19.2 

37.1 

59.9 

84.0 

118. 

163. 

216. 

278. 

6 

20.0 

38.5 

62.0 

87.0 

122. 

16.9. 

223. 

287. 

6V3 

21.5 

41.2 

66.3 

93.2 

131. 

180. 

236. 

304. 

7 

23.0 

43.9 

70.5 

99.3 

139. 

191. 

250. 

321. 

7Va 

24.6 

46.6 

74.8 

106. 

147. 

202. 

264. 

338. 

8 

26.1 

49.4 

79.0 

112. 

156. 

213. 

278. 

355, 

8Va 

27.6 

52.1 

83.3 

118. 

164. 

223. 

292. 

372. 

9 

29.2 

54.8 

87.6 

124. 

173. 

234. 

306. 

389. 

9Va 

30.7 

57.6 

9i.8 

130. 

181. 

245. 

319. 

406; 

10 

32.2 

60.3 

96.1 

136. 

189. 

256. 

333. 

423. 

lOVa 

33.8 

63.0 

101. 

142. 

198. 

267. 

347. 

440. 

11 

35.3 

65.7 

105. 

14S. 

206. 

278. 

361. 

457. 

11  Va 

36.8 

68.5 

109. 

155.* 

214. 

289. 

375. 

474. 

12 

38.4 

71.2 

113. 

161. 

223. 

3QQ. 

388, 

491. 

Heads. 

1,8 

5.7 

10.9 

13.4 

22.2 

38,0 

'57.0 

82;0 

HANDBOOK   ON    ENGINEERING. 

TABLE  NO.  15. 

Weight  and  Strength  of  Iron  Bolts. 


ENDS  ENLARGED  OR  UPSET. 

ENDS  NOT  EN- 
LARGED. 

ENDS  ENLARGED  OR.  UPSET. 

ENDS  NOT  EN- 
LARGED. 

8 

|; 

8 

*g 

fe 

tfx 

O 

*  fc 

By 

*g 

fc  5 

P5    . 

g    . 

fr  « 

oS 

rt 

"g 

El 

B§ 

'Eg 

i.S 

B  H' 

w  K 

ng 

5  g 

62 

gg 

JS_ 

°0 

r 

H 

3  * 

£ 

3  S 
p 

2o 

r 

§a 

i1 

Ine. 

Pounds. 

Tons. 
2340  Ibs. 

Ins. 

Lbs. 

Ins. 

Lbs, 

Tons 
2240  Ibs. 

Ins. 

Lbs. 

V/L 

.0414 

.245 

1% 

8.10 

45.7 

2.14 

12«0 

& 

.093 

.553 

If! 

8.69 

49.0 

2.22 

12.9 

I  6 

.165 

.983 

.35 

.321 

•*•  1  6 

1% 

9.30 

52.5 

2.30 

13.8 

JL 

.258 

1.53 

-43 

.452 

9.93 

56.0 

2.38 

,14.7 

% 

.372 

2.21 

.50 

.654 

216 

10.6 

59.7 

2.45 

f!5.7 

ft 

.506 

3.00 

.58 

.    .897 

oys 

12.0 

63.8 

2.59 

17-5 

V* 

.661 

3,93 

.66 

'  1.14 

2Vi 

13.4 

71.6 

2.73 

19.5 

ft 

.837 

4.97 

.73 

1.41 

2% 

14.9 

79.7 

2.88 

,21.6 

% 

1.03 

6.14 

.80 

1.67 

2Vfc 

16.5 

88.4 

3.02 

'23.9 

li 

1.25 

7.42 

.88 

2.03 

2% 

18.2 

97.4 

3.16 

26.1 

1.49 

8.83 

.96 

2.41 

2% 

20.0 

106.9 

3.30 

28.5 

1* 

1.75 

10.4 

1.04 

2.81 

21.9 

116.8 

3.45 

31.1 

2.03 

12.0 

1.12 

3.26 

3 

23.8 

127.2 

3.60 

[33.9 

M 

2.33 

13.8 

1.20 

3.77 

3V4 

27.9 

141.0 

3.86 

39.1 

i 

2'.65 

15.7 

1.27 

4.27 

32.4 

163.6 

4.12 

44.4 

ift 

2.99 

16,8 

1.35 

4.77 

3% 

37.2 

187.7 

'4.41 

51.0 

1% 

3.35 

18.9 

1.42 

5.28 

4 

42.3 

213.6 

4.70 

57.8 

1ft 

3.73 

21.1 

1.49 

5.81 

4Vi 

47.8 

227.0 

4.98 

65.2 

1% 

4*13 

23.3 

1.55 

6.39 

53.6 

254.5 

5.25 

72.9 

1ft 

4.56 

25.7 

1.64 

7.04 

4«I 

59.7 

283.5 

5.53 

'80.5 

1% 

5.00 

28.2 

1.72 

7,74 

5 

66.1 

314.2 

5.80 

88.1 

1ft 

~5.47 

30.8 

1.80 

8.48 

5^4 

72.9 

324.7 

6.08 

97.0 

5.95 

33,6 

1.87 

9.20 

51/2 

80.0 

356.4 

6.36 

106. 

1ft 

6.46 

36.4 

1.94 

9.88 

534 

87.5 

389.5 

6.63 

116. 

1% 

6.99 

394 

2.00 

10.6    ' 

6 

95.2 

424.1 

6.90 

126. 

JJi 

,7.53 

42.5 

2.07 

11.3 

For  square  Jbarslncrease  the  breaking  strains  Vi  part. 

A  long  upset  rod  is  no'strpngcr  than  one  not  upset,  against  slowly  ap* 
plied  loads  or  strains.'  Therefore  in  such  cases  the  column  of  kireate'st  diam- 
eter in  the  table  should  be  used. 


HANDBOOK    ON    ENGINEERING. 


907 


TABLE  NO.  16. 

Boiling:  Point*  of  Various  Substances. 
At  Atmospheric  Pressure  at  Sea  Level. 


Substance. 

Degrees 
Fahr. 

Substance. 

Degrees 
Fahr. 

Alcohol  

173 

Sulphur  

670 

Ammonia.  ...           

28 

Sulphuric  Acid,  s.  g  1.848 

590 

Benzine 

176 

Sulphuric  Acid,  s.  g.  1  3 

240 

Coal  Tar  

325 

Sulphuric  Ether    .  .         ...     . 

100 

Linseed  Oil 

597 

315 

Mercury      

648 

Water           

212 

Naptha...  

186 

Water,  Sea  

213.2 

Nitric  Acid,  s.  g.  1.42.  .   .  . 

248 

Water,  Saturated  Brine  

226 

Nitric  Acid,  s.  g.  1  5. 

210 

Wood  Spirit 

150 

Petroleum  Rectified 

316 

TABLE 

Melting  Points  of  Metals. 
From  D.  K.  C. 

NO.  17. 

Melting:  Points  of   Various  Solids. 
From  D.  K.  C.  and  H. 

Metal. 

Degrees 
Fahr. 

Substance. 

Degrees 
Fahr. 

Aluminum 

Full  Red 
Heat. 
1150 
507 
1690 
1996 
2156 
2282 
2012 
(    1922 
]     to 
C   2012 
.2912 
617 
—39 
1873 
(   2372 
<     to 
(   2552 
442 
773 

Carbonic  Acid         

-108 
2377 
32 
95 
45 
112 
91 
606 
120 
(     109 
to 
(     120 
239 
92 
14 
142 
154 

Antimony  

Glass  

Bismuth  

Bronze 

Lard 

Copper  

Nitro-Glycerine  

Gold,  Standard. 

Gold,  Pure  

Pitch      

Iron,  Cast,  Gray 

Saltpetre      

Iron,  Cast,  White 

Iron,  Wrought 

Lead 

Mercury  ...           ... 

Tallow       

Silver    .  . 

Steel  

Wax,  Bleached  

Tin  

Zinc 

Melting:  Points  of  Fusible  Plugs. 
From  D.  K.  0. 


Softens  at 

Melts  at 

Softens  at 

Melts  at 

2  Tin,  2  Lead  

365 

372 

2  Tin,  7  Lead  

377J 

S88 

Tin,  6  Lead  

372 

383 

2  Tin,  8  Lead  

3954 

408 

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iJlO  HANDBOOK    ON    ENGINEERING. 

TABLE  NO.  20. 

Capacity  of  Reservoirs  in  Gallons. 

NOTE  — The  columns  headed  Length  and  Width  denote  the  length  and  width 
in  feet;  the  columns  headed  Gallons  denote  the  capacity  In  U.  S.  gallons  for  one 
foot  In  depth. 


Length 
and 
Width 

Gallons. 

Length 
aud 
Width. 

Gallons. 

Length 
and 
Width. 

Gallon*. 

Length 
and 
Width. 

Gallons, 

1x1 
2x  1 

7.481 
14.961 

15  x   7 
16  x  7 

785.455 
837.818 

23x10 
24  x  10 

1720.519 
1795.325 

13x13 
14x13 

1264.208 
1361.454 

3X  1 

22.442 

17  x  7 

890.182 

25x10 

1870.130 

15x13 

1458.701 

2X  2 

29.922 

18  x   7 

942.545 

26x10 

1944.935 

16x13 

1555.948 

3x  2 

44.883 

19  x   7 

994.909 

27x10 

2019.740 

17x13 

1653.195 

4x  2 

59.844 

20x   7 

1047.273 

28x10 

2094.545 

18x13 

1750.442 

6x  2 

74.805 

21  X   7 

1099.636 

29X10 

2169.351 

19x13 

1847.688 

6x  2 

89.766 

8x    8 

478.753 

30X10 

2244.156 

20x13 

1944.935 

8x3 

67.325 

9X   8 

538.597 

11X11 

905.143 

21x13 

2042.182 

4x3 

89.766 

10  x   8 

598.442 

12X11 

987.429 

22x13 

2139.429 

6x  3 

112.208 

11x8 

658.286 

13X.11 

1069.714    . 

23x13 

2236.675 

6x  3 

134.649 

12  x  8 

718.130 

14X11 

1152.000 

24  x  13 

2333.922 

7X  3 

157.091 

13  x   8 

777.974 

15X11 

1234.286 

25  x  13 

2431.169 

8x  3 

179.532 

14  X   8 

837.818 

16X11 

1316.571 

26x13 

2528.416 

9x  3 

201.974 

15  x   8 

897.662 

17X11 

1398.857 

27x13 

2625.662 

4X4 

119.688 

16  x   8 

957.507 

18X11 

1481.143 

28  x  13 

2722.909 

6x  4 

149.610 

17  x   8 

1017.351 

19x11 

1563-429 

29x  13 

2820.156 

6x  4 

179.532 

18  x   8 

1077.195 

20X11 

1645.714 

30  x  13 

2917.403 

7x  4 

209.455 

19  x   8 

1137.039 

21X11 

1728.000 

31  x  13 

3014.649 

8x  4 

239.377 

20x   8 

1196.883 

22x11 

1810.286 

32  x  13 

3111.896 

fix  4 

269.299 

21  x   8 

1256.727 

23x11 

1892.571 

33  x  13 

3309.143 

10  x  4 

299.221 

22x   8 

1316.571 

24x11 

1974.857 

34X  13 

3306.390 

11  X  4 

329.143 

23x   8 

1376.416 

25X11 

2057.  143 

35  x  13 

3403.636 

12  X  4 

359.065 

24X   8 

1436.260 

26x11 

2139.428 

36  x  13 

3500.883 

6x  5 

187.013 

9x   9 

605.922 

27X11 

2221.714 

37x13 

3598:130 

6x  5 

224.416 

10  x   9 

673.247 

28x11 

2304.000 

38x13 

3695.377 

7x  6 

261.818 

11  x   9 

740.571 

29x11 

2386.286 

39x13 

3792.623 

8x  5 

299.221 

12  x  9 

807.896 

30  x  11 

2468.571 

14  x  14 

1466.182 

9x  5 

336.623 

13  x  9 

875.221 

31x11 

2550.857 

15x14 

1570.909 

10  x  6 

374.026 

14"  x  9 

942.545 

32x11 

2633.143 

16x14 

1675.636 

11  x  5 

411.429 

15  x   9 

1009.870 

33  x  11 

2715.429 

17  x  14 

1780.363 

12  x  5 

448.831 

16  x   9 

1077.195 

12x12 

1077.195 

18  it  14 

1885.091 

13  x  6 

486.234 

17  x  9 

1144.519 

13x12 

1166.961 

19x14 

1989.818 

14  X  5 

623.636 

18  x  9 

1211.844 

14  x  12 

1256.727 

20x  14 

2094.545 

15  x  5 

561.039 

19  x   9 

1279.169 

15  x  12 

1346.493 

21  XI4 

2199.263 

ex  6 

269.299 

20x  9 

1346.493 

16x12 

1436.260 

22x14 

2304.000 

7x  6 

314.182 

21  x   9 

1413.818 

17x12 

1526.026 

23  x  14 

2408.727 

8x  6 

359.065 

22x  9 

1481.143 

18x12 

1615.792 

24  x  14 

2513.454 

Ox  6 

403.948 

23x   9 

1548.467 

19x12 

1705.558 

25  x  14 

2018.182 

10  x  6 

448.831 

24  x   9 

1615.792 

20  x  12 

1795.325 

•26  X  14 

2722.909 

U  x  6 

•493.714 

25x   9 

1683.117 

21x12 

1885.091 

27  x  14 

2827.636 

12  x  6 

538.597 

26  x   9 

1750.442 

22  x  12 

1974.857 

28x14 

2932.364 

13  x  6 

583.480 

27x    9 

1817.766 

23x12 

2064.623 

29x14 

3037.091 

14  x  6 

628.364 

10  x  10 

748.052 

24x18 

2154390 

30X14 

3141.818 

15  x  6 

673.247 

11  x  10 

822.857 

25  x  12 

2244.156 

31  X14 

3246.545 

16  x  6 

718.130 

12  x  10 

897.662 

26x12 

2333.922 

32x14 

3.351.273 

17  x  6 

763.013 

13  x  10 

972.467 

27  x  12 

2423.688 

33x14 

3456.000 

18  x  6 

807.896 

14x10 

1047.273 

28  x  12 

2513.455 

34x14 

3560.727 

7x  7 

366.545 

15  x  10 

1122.078 

29  x  13 

2603.221 

35x14 

3665.454 

8x  7 

418.909 

16x10 

1196.883 

30  x  12 

2692.987 

*36  X  14 

3770.182 

9x  7 

471.273 

17  x  10 

1271.688 

31  x  12 

2782.753 

37x14 

3874.U09 

10  x  7 

523.636 

18  x  10 

1346.493 

33s  12 

2872.520 

38.x  14 

3/79.636 

11  x  J 

576.000 

19  x  10 

1421.299 

33  x  13 

2962.386 

,'J9  x  14 

4084.364 

12  x  7 

628.364 

20  x  10 

1496.104 

34  x  12 

3052.052 

40  x  14-x 

4189.091 

13  X  7 

680.727 

21  x  10 

1570.909 

35x12 

3141.818 

41x14 

4393.818 

14X  7 

733.091 

22X10 

1645.714 

36  XW 

3231.585 

42x14 

4398.545 

HANDBOOK    ON   ENGINEERING. 

TABLE  NO.  21. 

Oapaoity  of  Reservoirs  in  Gallons.  —  Continued. 


911 


Length 

Length 

Length 

Length 

and 

Gallons. 

and 

Gallons. 

and 

Gallons 

and 

Gallons. 

Width 

Width. 

Width. 

Width. 

15  x  15 

16  x  15 

1683.117 
1795.326 

28X17 
29X17 

3560.727 

3687.896 

33x80 
34  x20 

4937  143 
5086.753 

52x28 
54  x28 

"ioSi'ese 

11310.545 

17  x  15 

1907.532 

80X17 

3815.065 

35x20 

5236.364 

56  x  28 

11729.454 

18  x  15 

2019.740 

81X17 

3942.234 

36x20 

5385.974 

30  x30 

6733.467 

10  x  15 

2131.948 

82x17 

4069.403 

37  x20 

5535584 

32x30 

7181.299 

20X15 

2244.156 

33X17 

4196.571 

38x20 

5685  195 

34  x30 

7630130 

21  X  15 

2356.364 

34  x  17 

4323.740 

39x20 

5834.805 

36  X30 

8078.961 

82X-15 

2468.571 

18  X  18 

2423.688 

40x20 

5984.416 

38x30 

8527.792 

23X15 

2580.779 

19X18 

2558338 

'23x22 

3620  571 

40x30 

8976.623 

24X15 

2692.987 

20X18 

2692.987 

24x22 

3949  714 

42x30 

9425.454 

25X15 

2805.195 

21X18 

2827.636 

26x22 

4278.857 

44  x30 

9874.286 

26X15 

2917.403 

22X18 

.   2962.286 

28x22 

4608.000 

46X30 

10323.117 

27X15 

8029.610 

23X18 

3096.935 

30x22 

4937  143 

48x30 

10771.948 

28X15 

3141.818 

24X18 

3231.584 

32x22 

5266.286 

50  x30 

11220.770 

29X15 

3254.026 

25X18 

3366.234 

34x22 

5595.429 

52x30 

11669.610 

30X15 

3366.234 

26X18 

3500.883 

36  x22 

5924.571 

54  X30 

12118.442  . 

31  X15 

3478.442 

27X18 

3635.532 

38x22, 

6258.714 

56x30 

125H7.273  « 

32X15 

3590.649 

28X18 

3770.183 

40x22 

6582.857 

58x30 

13016.104 

33  X  15 

3702.857 

29X18 

3904.831 

43x32 

6912.000 

60x30 

13464.  y35    • 

34X15 

3815.065 

30X18 

4039.480 

44x22 

7241.143 

32x32 

7660.052 

35X15 

3927.273 

31X18 

4174.130 

24x24 

4308.779 

34x33 

8138.805 

86X15 

4039.480 

32X.18 

4308.779 

26x24 

4667.844 

36  x  32 

n    8617.558 

37X15 

4151.688 

33X18 

4443.429 

28x24 

5026.909 

38x32 

9098.312. 

88X15 

4263.896 

34X18 

4578.078 

30x34 

5385.974 

40  x  32 

9575.065 

39  X  15 

4376.104 

35X18 

4712.727 

32x24 

5745.039 

42  X  32 

10053.818 

40X15 

4488.312 

36X18 

4847.377 

34x24 

6r04.104 

44  x33 

10532.571 

41X15 

4600.519 

19  x  19 

2700.467 

36x24 

6463.169 

46x32 

11011.325 

43X15 

4718.727 

20  X  19 

2842.597 

38x24 

6822.234 

48  x  32 

11490.078 

43X15 

4824.935 

21  xi9 

2984.727 

40x24 

7181  299 

50x32 

11968.831 

44X15 

4937  143 

22  x  19 

3126.857 

42  x  24 

7540.364 

52x33 

\  2447.  584 

45X15 

5049.351 

.  23  x  |9 

3268.987 

44x34 

7899.429 

54x32 

12926.338 

16x16 

1915.013 

24  X  19 

3411.117 

46x24 

8258.493 

56  x  32 

13405.091 

17X16 

2034.701 

25  x  19 

3553.247 

48  x  24 

8617.558 

58x33 

13883.844 

18X16 

2154.390 

26  X  19 

3695.377 

26^26 

5056.831 

60x32 

143C2.597 

19x16 

2274.078 

27  X  19 

3837.506 

28x26 

5445.818 

62x32 

,14841.351 

20x16 

2393.766 

28  X  19 

3979.636 

30x26 

5834.805 

64x34 

1  15320.  104 

21X16 

2513.454 

29X19 

4121.766 

32x26 

6223.792 

34x34 

8647.480 

22X16 

2633.143 

30X19 

4263.896 

34x36 

6612.779 

36x34 

0156.156 

23X16 

2753.831 

31  X19 

4406.026 

86x26 

7001.766 

38x34 

0664.831 

24X16 

2872.519 

32  x  19 

4548.156 

38x26 

7390.753 

40x34 

10173.506 

25X16 

2992.208 

33X19 

4690.286 

40x26 

7779.740 

4*x34 

10682.182 

26X16 

3111.896 

34X19 

4832.416 

42x26 

8168.727 

44x34 

11190.857 

27  x  16 

3231  584 

35X19 

4974.545 

44  x26 

&557.714 

46x34 

11699.532 

28X16 

3351.273 

36  x  19 

5116.675 

46x26 

8946.701 

4»x34 

12208.308 

29  x  16 

3470.961 

87  x  19 

5258.805 

48x26 

9835.688 

50x34 

12716.883 

80  x  16 

3590649 

38  x  19  - 

5400.935 

50x26 

9724.675 

62x34 

13225.558 

81  X  16 

3710.338 

20x20 

2992.208 

52x26 

10113.662 

54x34 

13734.231  . 

82  x  16 

3830.026 

21  x20 

3141.818 

28x28 

5864.727 

56x34 

14242.900 

17  x  17 

2161.870 

22x20 

3291.429 

30x28 

6283.636 

58x34 

14751.584 

18  x  17 

2289.039 

23x20 

3441.039 

32x28 

6702.545 

60x34 

15260.260 

19  x  17 

2416.208 

24x20 

3590.649 

34x28 

7121.454 

62  x  34 

15768.935 

20  x  17 

2543.377 

25x20 

3740.260 

36x28. 

7540.364 

64x34 

16377.610 

21  X  17 

2670.545 

26x20 

3889.870 

38x28 

7959.273 

66x34  , 

16786.286 

22  x  17 

2797.714 

27  X20 

4039.480 

;40x28 

8378.  182 

68x34 

17394.961 

23  x  17 

2924.883 

28x20 

4189.091  , 

142  x  28 

8797.091 

36x36 

9694,753 

24  x  17 

3052.062 

29.x  20 

4338.701 

f  44  x  28 

9216.000 

38  x  36 

10233.351 

25x  17 

3179.221 

80  x20 

,    4488.312 

46x28 

9634.909 

40x36 

10771.948 

26  x  17 

3306.390 

31  X  20 

4637.922 

48x28 

10053.818 

43x36 

11310.545 

27  x  17 

3433.558 

82x20 

4787.532 

50x38 

10472.727 

44x36 

11849.143 

The  United  States  inspection  laws  allow  20  per  cent  more  pressure  to  b<| 
carried  on  boilers  with  double  -riveted  longitudinal  seams,  than  on  single  rlveteU 
ooilera. 

912 


HANDBOOK   ON   ENGINEERING. 


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HANDBOOK   ON   ENGINEERING. 


913 


TABLE  NO.  23. 

Properties  of  Saturated  Steam. 


Pressure 
per  Square 
Inch. 

Pressure 
Above 
Zero. 

Temperature. 

Latent  Heat. 

Total  Heat 
Above  Lero. 

Weight  of 
One 
CubicFoot 

Inches  of 
Mercury. 

Pounds 
per  Square 
Inch. 

Fahr.  Deg. 

B.  T.  U. 

Fahr.,  B.  T.  U. 

Pounds. 

2.04 

1 

102  00 

1042  96 

1145  05 

0030 

4  07 

2 

126  26 

1026  01 

1152  45 

.0058 

6.11 

3 

141.62 

1015  25 

1157  13 

.0085 

8  14 

4 

153  07 

1007  22 

1160  62 

0112 

10  18 

5 

1K2.23 

1000  72 

1163.44 

0137 

12  22 

6 

170  12 

995.24 

1165  82 

.0163 

14  25 

7 

176.91       . 

990  47 

1167  89 

0189 

16.29 

8 

182.91 

986.24 

1169.72 

0214 

18  32 

9 

188  31 

9*2.43 

1171  37 

.0239 

20  36 

10 

193  24 

978  95 

1172  87 

.0264 

22  39 

11 

197  76 

975  76 

1174  25 

0289 

24  43 

12 

201.96 

972.80 

1175.53 

.0313 

'26  46 

13 

205  88 

970  02 

1176  73 

.0337 

28  51 

14 

209  56 

967.42 

1177  85 

0362 

Gauge  Press. 

14  7 

212  00 

965  7 

1178.10 

.0380 

3 

15 

213.02 

964  97 

1178.91 

.0387 

1  3 

16 

216.29 

962.65 

1179.90 

0413 

2  3 

17 

219  41 

960  45 

1180  85 

.0437 

3  3 

18 

222  37 

958  34 

1181  76 

.0462 

4.3 

19 

225.20 

956  34 

1182.61 

.0487 

6.3 

20 

227.91 

954.41 

1183  45 

.0511 

6.3 

21 

230  51 

952  57 

1184.24 

.0536 

7  3 

22 

233.01 

950  79 

1185.00 

.0561 

83 

2.5 

235.43 

949  07 

118>.74 

.0585 

93 

24 

237.75 

947  42 

1186  45 

.0610 

10.3 

25 

240.00 

945  82 

1167.13 

.0634 

11  3 

26 

242.17 

944.27 

1187  80 

.0658 

12  3 

27 

244  28 

942  77 

1188  44 

0683 

is.  a 

28 

246  32 

941  32 

1189.06 

0707 

14  3 

29 

248.31 

939  90 

1189  67 

0731 

15.3 

30 

250  24 

938  92 

1190  26 

.0755 

16  3 

31 

252  12 

937  18 

1190  83 

.0779 

17  3 

32 

253.95 

935  88 

1191  39 

0803 

18.8 

38 

255.73 

934.60 

1191  93 

0827 

19  3 

34 

257  47 

933  36 

1192  46 

.0851 

20.3 

35 

259.17 

932  15 

1192  98 

.0875 

21  3 

36 

260.83 

930  96 

1193  49 

.0899 

22.3 

87 

262  . 

929  80 

1193.98 

.092- 

23  3 

38 

264  04 

928.67 

1194  47 

.0946 

24  3 

89 

265  59 

927.56 

1194.94 

0970 

25  3 

40 

267.12 

926.47 

1195.41 

.0994 

26  1 

41 

268.61 

925.40 

1195  86 

.1017 

27  3 

42 

270.07 

924  35 

1196  31 

.1041 

58 


914 


HANDBOOK    ON    ENGINEERING. 


TABLE  NO.  24. 

Properties  of  Saturated  Steam— Continued. 


Gauge 
Pressure. 

Pressure 
Above 
Zero. 

Temperature. 

Latent  Heat. 

Total  Heat. 
Above  Zero. 

Weight  ot 
one 
Cubic  Foot 

Pounds 

Pounds 

per  Square 

per  Square 

Fahr.  Deg. 

B.  T.  U. 

Fahr.,B.T.U. 

Pounds. 

Inch. 

Inch. 

28.3 

43 

271  50 

923.33 

1196.74 

.1064 

29  8 

44 

272  91 

922.32 

1197.17 

.1088 

30.3 

45 

274.29 

921  33 

1197.WO 

.1111 

31  8 

46 

275  65 

920.36 

1198  01 

.1184 

32.3 

47 

276  98 

919.40 

1198.42 

.1158 

38  3 

48 

278  29 

918  46 

1198  82 

.1181 

34.3 

49 

279  58 

917.54 

1199.21 

.1^04 

35.  8 

60 

280.85 

916.63 

1199.60 

.1227 

36.3 

61 

282.09 

915.73 

1199  98 

.1251 

37.8 

62 

283  32 

914.85 

1200.35 

.  1274 

38  3 

53 

284.53 

913  98 

1200  72 

.  1297 

39  3 

54 

285.72 

913.13 

1201.08 

.1320 

40.3 

65 

236.89 

912  29 

1201  44 

.1343 

41.3 

56 

2S8.05 

911  46 

1201.79 

1366 

42.3 

57 

289  11 

910.64 

1202.14 

1388 

43  8 

68 

290  31 

909.83 

1202.48 

.1411 

44.3 

69 

291  42 

909.03 

1202.82 

1434 

45.3 

60 

292  52 

908.24 

1203  15 

.1457 

46.3 

61 

293  59 

907  47 

1203  48 

.1479 

47.3 

62 

294.66 

906.70 

1203.81 

.1502 

48.8 

63 

295.71 

90.3.94 

1204.13 

.1524 

49  8 

64 

296.75 

905.20 

1204.44 

.1347 

60.3 

65 

297.77 

904  46 

1-204.76 

.1569 

61  3 

66 

298.78 

903.73 

1205.07 

.1592 

62  8 

67 

299.78 

903.01 

12U5  37 

.1614 

53  3 

68 

800  77 

902.29 

1205  67 

.1637 

54.3 

69 

301.75 

901.59 

1205.97 

.1659 

55.3 

70 

802.71 

900.89 

1206.26 

.1681 

66.3 

71 

303.67 

900  21 

1206  56 

.1708 

67.3 

78 

304  61 

899.52 

1200  84 

.1725 

68.8 

73 

805  55 

898  85 

1207.13 

.1748 

59.8 

74 

306.47 

898  18 

1207  41 

.1770 

60.8 

75 

307  88 

897  52 

1207  69 

1792 

61  8 

76 

308.29 

896.87 

1207.96 

1814 

62.3 

77 

309.18 

896  23 

1208.24 

.1836 

68.8 

78 

310.^6 

895  69 

1208  51 

.1857 

64.8 

79 

310.  i,4 

894.95 

1208  77 

.1879 

65  3 

80 

314.81 

894  33 

1209  04 

.1901 

66  3 

81 

312.67 

893  70 

1209  30 

.1923 

67-8 

82 

313  52 

893  09 

1209  56 

.1945 

68  3 

83 

314.36 

892  48 

1209  82 

.1967 

69.3 

84 

315.19 

891  88 

1210.07 

.1988 

70  3 

85 

316  02 

891  28 

1210.32 

.2010 

71.8 

86 

316.83 

890  .  69 

1210.57 

.2082 

72.8 

87 

317.65 

890.10 

1210  82 

.2053 

HANDBOOK    ON    ENGINEERING. 


915 


TABLE  NO.  25. 

Properties  of  Saturated  Steam  —  Continued. 


Gauge 
Pressure. 

Pressure 
Above 
Zero. 

Temperature 

Latent  Heat. 

Total  Heat. 
Above  Zero. 

Weight  of 
One 
CubicFoot. 

Pounds 

Pounds 

per  Square 

per  Square 

Fahr.  Deg. 

B.  T.  U. 

Fahr.,B.T.U. 

Pounds. 

Inch. 

Inch. 

73.8 

88 

318  45 

889.52 

1211.06 

.2075 

74  8 

89 

319.24 

888.94 

1211.81 

.2097 

75  3 

90 

320.03 

888.37 

1211.55 

.2118 

76.3 

91 

820.82 

837  80 

1211.79 

.2130 

77.3 

92 

321  59 

887.24 

1212  02 

.2160 

78.3 

93 

322  36 

886  68 

1212.26 

.2182 

79.8 

94 

323  12 

886.13 

1212.49 

.2204 

80  3 

95 

323  88 

885.58 

1212.73      . 

.2224 

81.3 

96 

824  63 

885.04 

1212.95 

.2245 

82.3 

97 

325.37 

884.50 

1213.18 

2266 

88  3 

98 

326  11 

883  97 

1213.40 

.2288 

84.3 

99 

326.84 

883  44 

1213  62 

.2309 

85.8 

100 

327  57 

882.91 

1213.84 

.2330 

86.3 

101 

328  29 

882  39 

1214.06 

.2301 

87  3 

102 

329  00 

881  87 

1214.28 

2371 

88.3 

103 

829  71 

881-35 

1214.50 

.2392 

89.8 

104 

330.41 

880  84 

1214.71 

.2418 

90  3 

105 

331.11 

880.34 

1214.92 

.2434 

91.3 

106 

381.80 

879.84 

1215.14 

.2454 

92.8 

107 

332  49 

879  34 

1215.35 

.2475 

93.3 

108 

333  17 

878  84 

1215.56 

.2496 

94.3 

109 

333.86 

878  35 

1215.76 

.2616 

95.8 

110 

834.52 

877  86 

1215  97 

.2537 

96.3 

111 

335  19 

877  37 

1216.17 

.2558 

97  .3 

112 

335  85 

876.89 

1216.37 

.2578 

98  3 

113 

336.51 

876  41 

1216.57 

.2599 

99.3 

114 

337  16 

875  94 

1216.77 

.2619 

100  3 

115 

337.81 

875.47 

1216  97 

.2640 

101.3 

116 

838  45 

875  40 

1217.17 

.2661 

102  3 

117 

339.10 

874.53 

1217.36 

.2681 

103  3 

118 

339  73 

874.07 

1217  66 

.2702 

104  3 

119 

340  36 

873  61 

1217  75 

2722 

105  8 

120 

340.99 

873  15 

1217  94 

.2742 

106  H 

121 

311  61 

872  70 

1218.13 

.2762 

107  3 

122 

342.23 

872  25 

1218.32 

.2782 

108.8 

123 

342  85 

871  80 

1218.51 

.2802 

109  3 

124 

343  46 

871  35 

1218.69 

.2822 

110  3 

125 

344  07 

870  91 

1218.88 

.2842 

111.3 

126 

344  67 

870  47 

121906 

.2862 

112  8 

127 

845  27 

870  03 

1219.27 

.2882 

113.3 

128 

345  87 

869.59 

.       121943 

.2902 

114.3 

129 

346.45 

869  16 

1219.61 

2922 

115.3 

130 

347.05 

868.73 

1219  79 

.3942 

116  8 

131 

347.64 

868.30 

1219.97 

2961 

916 


HANDBOOK    ON    ENGINEERING. 


TABLE  NO.  26. 

Properties  of  Saturated  Steam  — Continued. 


Gauge 
Pressure. 

Pressure 
Above 
Zero. 

Temperature. 

Latent  Heat. 

Total  Heat. 
Above  Zero. 

Weight  of 
One 
CublcFoot. 

Pounds 

Pounds 

per  Square 

per  Square 

Fahr.  Deg. 

B.  T.  U. 

Fahr.,  B.  T.  U 

Pounds. 

Inch. 

Inch. 

117.3 

13-2 

348  22 

867.88 

1220  15 

.2981 

118  3 

133 

348.80 

867  46 

1^0  32 

.3001 

119.3 

134 

349.38 

867.03 

It'iU  50 

.3020 

120  3 

135 

349.95 

866  62 

U<0  67 

.  3u»() 

121  3 

136 

350.52 

866  20 

12-/0  85 

.3u60 

122.3 

137 

351.08 

866  79 

1221  02 

3u79 

123  3 

138 

351.75 

865.38 

1-^1  19 

3u99 

124.3 

139 

352  21 

864  97 

12.51  36 

.31i8 

125.3  " 

ito 

352.76 

864  56 

1221  53 

.3138 

126.3 

141 

363.31 

864.16 

1221  70 

.3158 

127  3 

142 

358.86 

863.76 

12-21  87 

.3178 

128.3 

143 

354.41 

863.36 

1222  03 

.3199 

129.3 

144 

354.96 

86-2.96 

1222.20 

3219 

130  3 

145 

355  50 

862  56 

1222  36 

.3*39 

131.3 

146 

356  03 

862  17 

1222.53 

.3209 

132.3 

147 

,85657 

861.78 

1*2-2  69 

.3'/79 

133.3 

148 

357.10 

861  39 

1222.85 

3299 

134  3 

149 

357  63 

861  00 

1223  01 

.3319 

135.3 

150 

358  16 

860.62 

1223.18 

.3340 

136  3 

151 

358  68 

860  23 

1223  33 

.3358 

137  3 

152 

359  20 

859.85 

1223  49 

.3376 

138  3 

153 

359  72 

859  47 

1223  65 

3394 

139.3 

154 

360.28 

859  10 

12-23  81 

.3412 

140.8 

155 

360.74 

858.72 

1223.97 

.3430 

141.3 

156 

361.26 

858  35 

1224.12 

.3448 

142.3 

157 

361.76 

857  98 

1224  28 

.3466 

143  3 

158 

362.27 

857.61 

1224.43 

.3484 

144  3 

159 

362.77 

857  24 

1224  58 

.3502 

145.3 

160 

363.27 

856.87 

1224.74 

.3520 

146.3 

161 

363  77 

856  50 

1224  89 

.3539 

147.3 

162 

364.27 

856.14 

1225.04 

.3558 

148.3 

163 

364  76 

855.78 

1225.19 

.3577 

149.  3 

164 

365  25 

855  42 

1225  34 

3596 

150.3 

165 

365.74 

855  06 

1225.49 

.3614 

151.3 

166 

366  23 

854  70 

12-25  64 

.3633 

153.3 

167 

366.71 

854  35 

1225.78 

3652 

153  3 

168 

367.19 

853  99 

1225.93 

.3671  • 

154.3 

169 

367  68 

853.64 

1226  08 

.8690 

155.3 

170 

368.15 

853.29 

1226.22 

.3709 

156.3 

171 

368.63 

852  94 

1226.37 

.3727 

157.3 

172' 

369.10 

852  59 

1226.51 

.3745 

158.3 

173      • 

369.57 

852.25 

1226  66 

3763 

159.3 

174 

870.04 

851.90 

1226  80 

3781 

160.3 

175 

370  51 

851.56 

1226.94 

.3791) 

161  3 

176 

370.97 

851  22 

1227.08 

.3817 

HANDBOOK   ON    ENGINEERING. 


917 


TABLE  NO.  27. 

Properties  of  Saturated  Steam  —  Continued. 


Gauge 
Pressure. 

Pressure 
Above 
Zero. 

Temperature. 

Latent  Heat. 

Total  Heat. 
Above  Zero. 

Weight  of 
One 
Cubic  Foot. 

Pounds 

Pounds 

per  Square 
Inch. 

per  Square 
Inch. 

Fahr.  Dcg 

B.  T.  U. 

Fabr.,  B.  T.  U. 

Pounds. 

162  3 

177 

371.44 

850.88 

1227  32 

.3835 

163  3 

178 

371  bO 

850  54 

1227-37 

.3853 

164.3 

179 

372  36 

850  20 

12-27.61 

.3871 

165.3 

180 

372.82 

849  86 

1227  65 

.3889 

166  3 

181 

373  27 

849  53 

1227  78 

.3907 

167.3 

182 

373  73 

849  20 

1227  92 

.3925 

168.3 

183 

374  18 

848  86 

1228.06 

.3944 

169  3 

184 

374  63 

848  53 

1228  20 

3962 

170.3 

185 

375  08 

848  20 

1228.33 

.3980 

171  3 

186 

375.52 

847.88 

1228.47 

.3999 

172  3 

187 

375  97 

847,55 

1228  61 

.4017 

173  3 

188 

376  .4-1 

847  22 

1228  74 

.4035 

174.3 

189 

376.85 

846  90 

1228  87 

.4063 

175.3 

190 

377  29 

846  58 

1229.01 

.4072 

176.3 

191 

377.72 

846.23 

1229.14 

.4089 

177  3 

192 

378  16 

845.91 

1229.27 

.4107 

178.3 

193 

378  59 

845  62 

1229.41 

.4125 

179  3 

194 

379  02 

845  30 

1229.54 

.4143 

180.3 

195 

379  45 

844.99 

1229.67 

.4160 

181.3 

196 

379  97 

844  68 

1229.80 

.4178 

182  3 

197 

380.30 

844  36 

1229.93 

.4196 

183.3 

198 

380  72 

84*  05 

1230.06 

.4214 

184.3 

199 

381.15 

843  74 

1230  19 

.4231 

185  3 

200 

381.57 

843  43 

1230.31 

.4249 

186.3 

201 

381  99 

84?  12 

1230  44 

.4266 

187.3 

202 

382.41 

84°  81 

1230  67 

.4283 

188  3 

203 

382  82 

8*?  50 

1230.70 

.4300 

189  3 

204 

383  24 

8'?  20 

1230  82 

.4318 

190  3 

205 

383.65 

841  89 

1230  95 

.4335 

191.3 

206 

384.06 

8*1  59 

1231  07 

.4352 

192  3 

207 

384.47 

8'  1.29 

1231.20 

.4369 

193  3 

208 

384.88 

840.99 

1231  32 

.4386 

194  3 

209 

385.28 

8^0.69 

1231  45 

.4403 

195.3 

210 

385  67 

840.39 

1231  57 

.4421 

918 


HANDBOOK  ON  ENGINEERING. 


TABLE  NO.  28. 


SWEDES  IRON  TRANSMIS- 

CRUCIBLE   CAST    STEEL 

SION   OR   HAULAGE 

TRANSMISSION    OR 

ROPES. 

HAULAGE  ROPES. 

7  Wires  ta  the  Strand.      Hemp 

7  Wires  to  the  Strand.      Hemp 

Centre. 

Centre. 

d 

d® 

bflOQ 

.«, 

d 

bo     OD 

•  . 

^ 

Diameter  in 
Inches. 

i  Price  per  Foot  1 
t  Cents. 

Breaking  Strai 
in  Tons  of  2.0C 
Pounds. 

Proper  Workln 
Load  in  Ton 
of  2,000  Lbs. 

ised  for  Derricki 
Ferries,  Trang 

Average  Weigh 
per  Foot. 

Minimum  Size 
of  Drums  or 
Sheaves  in  Ft 

Diameter  in 
Inches. 

Price  per  Foot 
in  Cents. 

Breaking  Strai 
in  Tons  of 
2,000  Pounds. 

Proper  Workm 
Load  in  Tons 
of  2,000  Pound 

sed  for  Derrick* 
jrries,  Transmie 

Average  Weigh 
per  Foot. 

Minimum  Size 
of  Drums  or 
Sheaves  in  Ft. 

9-32 
5-16 

3| 

1.4 
17 

i 

aS 

"5  "So 

a,  be  .; 

.15 

li 

J* 

9-32 
5-16 

4^ 

2| 

3 

I 

s£ 

.15 

3 

!7-16 

4| 

6i 

2  4 
3  3 

i 

£*~y  o 

§«* 

.22 
.30 

2 

2| 

7!6 

if 

5 

63 

1 

figs 

.22 
.30 

P 

9-16 
| 

8 
10 

4  2 
5.3 
6.6 

1 

m 

SSI 

.39 
.50 
.64 

| 

9-16 

| 

1\ 

9 
11 

83 

io| 

13 

2 

|2| 

.39 
.50 
.64 

1 

Tl-16 

12 

7.9 

i 

«*gpL, 

.75 

4 

11-16 

13i 

16 

3 

SJi  ij 

.75 

6* 

If 

14 

23 
29 
86 

9.3 
12. 
16. 
20. 
24. 

!   2-5 

;  1-5 

4-5 

CD   08«_, 

Hj 

.89 
1.20 
1.58 
2  00 
2.45 

1 

it 

16 
22 

28 
36 
43 

19 
24 
32 
40 

48 

? 

10 

e  Ropes 
s,  Steam 
L  of  Powe 

.89 
1.20 
1.58 
2.00 
2  45 

1 

]• 

43 

29. 

5  4-5 

J5s 

3  00 

8 

if 

51 

58 

12 

y>  rtQ 

3.00 

JIT 

H    • 

51 

34. 

7 

H 

8  55 

84 

if 

60 

68 

14 

go-s 

3  55 

13 

• 

HANDBOOK   ON   ENGINEERING. 


919 


TABLE  NO.  29. 


CRUCIBLE  CAST   STEEL 

SWEDES   IRON   PLIABLE 

PL       LE  HOISTING 

HOISTING  ROPES. 

ROPES. 

19  Wires  to  the  Strand.      Hemp 

ires  to  the  Strand.      Hemp 

Centre. 

Centre. 

a 

|| 

§1 

beg 

44 

bo 

,j 

a 

a 

*1 

bo 

O    QQ 

1 

«H 

I 

I 

fa 

£c* 
»* 

o  o1 

§•     ^ 

N  «* 

«25 

.9 

I 

L| 

03  O1 

EH  . 

l|* 

Ij 

(4 

)  0) 

if 

i1"1 

\  Price  per 
|  Cents. 

Breaking 
in  Tons  < 
Pounds. 

III 

ll? 

o  o 

g£ 

Minimum 
of  Drumi 
Sheaves 

Diameter 
Inches. 

Price  per 
Cents. 

Breaking 
in  Tons  < 

2,000  Pou 

Diam.  of 
Rope  of 
Strength 

cL^cT 

£3* 

|| 

Minimum 
Drums  o 

Sheaves 

>16 

9 

3 

? 

i! 

;i 

.  .10 
.15 
.22 

u 

5-16 
i 

P 

11.20 
1.70 
2.50 

9-16 

1 

.10 
15 
.22 

1 

-16 

10 

7 

li 

1  2-5 

.30 

2* 

7-16 

7* 

3.40 

1 

K 

.30 

•i 

t 

11 

9 

it 

1  4-5 

.39 

8 

4.40 

1$ 

1 

.39 

ii 

-16 

12 

11 

i  9-16 

2  1-5 

.50 

2§ 

9-16 

10 

5.60 

1  5-16 

1  1-10 

.50 

2 

14 

14 

1| 

24-5 

.64 

34 

12 

6  80 

1* 

If 

.64 

24 

18 

20 

21 

4 

.89 

4 

s 

16 

9.70 

if 

4 

.89 

3 

23 

26 

2| 

5  1-5 

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HANDBOOK    ON   ENGINEERING. 


TABLE  NO.  30. 


19  Wires  to  the  Strand.      Hemp 
Centre. 

WIRE  ROPE  FOR  INCLINED 
PLANES. 

For  the  benefit  of  those  desiring  to 
use     wire    rope     on     slopes,    inclined 
Planes,  etc  ,  a  table  by  which  the  strain 
produced   by  any  load  may  be  readily 
ascertained. 
This  table  gives  only  the  strain  pro- 
duced on  a  rope  by  a  load  of  one  ton  of 
two  thousand  pounds,  an  allowance  for 
rolling  friction  being   made.    An  addi- 
tional allowance  for  the  weight  of  the 
rope  will  have  to  be  made. 
Example:  For   an    inclination  of    100 
feet    in  100   feet,   corresponding   to  an 
angle  of  45°,  a  load  of  2,000  pounds  will 
produce  a  strain  on  the  rope   of   1,419 
pounds,  and  for  a  load  of  9,000  pounds 
the     strain      on     the     rope    will      be 

Inches. 

Price  per  Foot, 
in  Cents. 

Breaking  Strain 
in  Tons  of 
2,000  Pounds. 

Proper  Working 
Load  in  Tons 
of  2,000  Lbs. 

Average  Weight 
per  Foot. 

Minimum  Size 
of  Drums  or 
Sheaves  in  Ft. 

r-16 
i-,6 

k 

14 
15 
17 
19 
22 
28 
35 
45 
54 
65 
80 
95 
112 
136 
160 
220 

8 
10 
13 
15 

20 
30 
40 
50 
63 
76 
95 
115 
130 
160 
220 
235 

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13 
16 
19 
22 
25 
33 
40 

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.39 
.50 
.64 
.89 
1.20 
1.58 
2  00 
2  45 
3.00 
3.55 
4.15 
5.25 
6  30 
8.00 

2 

2* 

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5 
6 
7 

8 
9 
10 
11 
12 
13 
14 
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31"1 

5 
10 
1ft 

20 
25 
30 
35 
40 
45 
50 
65 
60 
65 
70 
75 
80 
85 
90 

11  1-5 
144 

19  1-5 
21  5-6 
24i 

28  5-6 
31 
33  1-12 
35 
37 
38f 
40i 
42 

112 
211 
308 
404 
497 
586 
673 
754 
832 
905 
975 
1,040 
1,100 
1,156 
1,210 
1,260 
1,304 
1,347 

95 
100 
105 
110 
115 
120 
125 
130 
135 
140 
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160 
165 
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1,487 
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1,570 
1,592 
1,614 
1,633 
1,653 
1,671 
1,689 
1,703 
1,717 
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6 
7 
8 
9 
10 
11 
12 

A  factor  of  safety  of  five  to  seven 
times  should  be  taken;  that  is,  the 
working  load  on  the  rope  should  only 
be  one-fifth  to  one-  seventh  of  its  break- 
ing strength.  As  a  rule,  ropes  for 
shafts  should  have  a  factor  of  safety  of 
five,  and  on  inclined  planes,  where  the 
wear  is  much  greater,  the  factor  of 
safety  should  be  seven. 


HANDBOOK    ON    ENGINEERING. 


921 


TABLE  NO.  81. 

Table  of  Transmission  of  Power  by  Wire  Ropes. 

This  table  is  based  upon  scientific  calculations,  careful  observations  and  expert* 
ence,  and  can  be  relied  upon  when  the  distance  exceeds  100  feet.  We  also  find  by 
experience  that  it  is  best  to  run  the  wire  rope  transmission  at  the  medium  number 
of  revolutions  indicated  in  the  table,  as  it  makes  the  best  and  smoothest  running 
transmission.  If  more  power  is  needed  than  is  indicated  at  80  to  100  revolutions, 
choose  a  larger  diameter  of  sheave. 


Diameter  of 
Sheave  in  ft. 

I 

Number  of 
Revolutions. 

Diameter  of 
Rope. 

Horse-Power. 

Diameter  of 
Sheave  in  Ft. 

Number  of 
Revolutions. 

^ 

Horse-  Power. 

3 

80 

i 

8 

.  7 

140 

9-16 

35 

3 

100 

3| 

8 

80 

i 

26 

3 

120 

I 

4 

8 

100 

32 

3 
4 

140 

80 

I 

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8 
8 

120 
140 

39 
45 

4 

100 

i 

5 

9 

80 

. 

47 

48 

4 

120 

1 

6 

9 

100 

9-16| 

58 

'   60 

4 

140 

1 

7 

9 

120 

9  16§ 

69 
73 

5 

80 

7-16 

9 

9 

140 

9  16$ 

82 
84 

5 

100 

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10 

80 

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64 
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5 

120 

7-16 

13 

10 

100 

f  11-16 

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80 
85 

5 

140 

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10 

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102 

6 

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12 

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9-16 

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100 

9-16 

25 

14 

80 

Hi 

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176 

7 

1-20 

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14 

100 

1  1* 

185 

922 


HANDBOOK    ON    ENGINEERING. 


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HANDBOOK   ON   ENGINEERING. 


923 


TABLE  NO.  33. 

Percentage   of   Power  Gained   by  Adding   a  Condenser,  the  Speed 
and  Point  of  Cut-Off  Remaining  the  Same.* 

VACUUM  •==  24.5   INCHES. 


Per  Cent 

Per  Cent 

Per  Cent 

Per  Cent 

M.  K.  P. 

of  Power 

M.  B.  P. 

of  Power 

M.  E.  P. 

of  Power 

M.  E.  P. 

of  Power 

Gained. 

Gained. 

Gained. 

Gained. 

5 

250 

17 

70.5 

38 

31,6 

62 

19.8 

6 

200 

18 

66.6 

40 

30 

64 

18.7 

7 

171.4 

19 

63.1 

42 

28.5 

66 

18.1 

8 

150 

20 

60 

44 

27.2 

68 

17.6 

9 

133.3 

22 

54.5 

46 

26.08 

70 

17.1 

10 

120 

24 

50 

48 

25 

72 

16.6 

11 

109 

26 

46.1 

50 

24 

74 

16.  S 

12 

100 

28 

44.3 

52 

23.07 

76 

15.7 

13 

92.3 

30 

40 

54 

22.2 

78 

15.9 

14 

85.7 

32 

37.5 

56 

21.4 

80 

15 

15 

80 

34 

35.2 

58 

20.6 

82 

14.63 

16 

76 

36 

33.3 

60 

20 

85 

14.12 

Calculated  gain  due  to  vacuum,  friction  not  considered. 


TABLE  NO.  34. 

glies  of   Cylinders   Usually  Furnished  for  Compound  Pumps,  and 
Corresponding  Ratios  of  Expansion. 


Diameter 
High  Pressure 
Cylinder. 

Diameter 
Low  Pressure 
Cylinder. 

Ratio 
of 
Expansion. 

6 

10 

2.78 

7 

12 

2.94 

8 

12 

2.25 

9 

14 

2.42 

10 

16 

2.56 

12 

18 

2.25 

14 

20 

2.04 

16 

24 

2.25 

18 

30 

2.77 

924 


HANDBOOK    ON    ENGINEERING. 


TABLE  NO.  35. 

Indicated  Horse-power  for  One  Pound  of  Mean  Pressure. 


Diameter  of 
Cylinder  in 
Inches. 

SPEED  ov  PISTON  IN  FEET  PER  MINUTE. 

240 

300 

350 

400 

450 

500 

550 

600 

6 

0-205 

0-256 

0-299 

0-342 

0-385 

0-428 

0-471 

0-513 

;y 

0-279 

0-348 

0-408 

0-466 

0-524 

0-583 

0641 

0-699 

8 

0-365 

0-456 

0-532 

0-608 

0-685 

0-761 

0-837 

0-912 

9 

0-462 

0-577 

0-674 

0-770 

0866 

0-963 

1154 

10 

0-571 

0-714 

0-833 

0-952 

1-071 

1-190 

1  \  A)§ 

1-428 

11 

0-691 

0-864 

1*008 

1-153 

1-296 

1-44 

1-584 

1-728 

12 

0-820 

1-025 

1-195 

1-366 

1-540 

1-708 

1-880 

2-050 

13 

0-964 

1-206 

1-407 

1-608 

1-809 

2-01 

1-211 

2-412 

14 

1-119 

1-398 

1-631 

1-864 

2-097 

2-331 

2-564 

2-797 

15 

1-285 

1-606 

1-873 

2131 

2-409 

2-677 

2-945 

3-212 

16 

1-461 

1-827 

2-131 

2-436 

2-741 

3-045 

3-349 

3-654 

17 

1-643 

2-054 

2*396 

2-739 

3-081 

3-424 

3-V66 

4-108 

18 

1-849 

2-312 

2-697 

3-083 

3-468 

3-854 

4-239 

4-624 

19 

2-061 

2-577 

3-006 

3-436 

3-865 

4-297 

4-724 

5-154 

20- 

2-292 

2-855 

3-331 

3-807 

4-285 

4-759 

5-234 

5-731 

^21 

2-518 

3148 

3-672 

4-197 

4-722 

5-247 

5-771 

6-296 

22 

2-764 

3-455 

4-031 

4-607 

5-183 

5-759 

6-334 

6-911 

25 

3-021 

3-776 

4-405 

5-035 

5-664 

6-294 

6-923 

24 

3-289 

4-111 

4-797 

5-482 

6167 

6-^3 

7-538 

8*223 

25 

3-569 

4-461 

5-105 

5-948 

6-692 

7-436 

8173 

8-923 

26 

3-861 

4-826 

5-630 

6-435 

7-239 

8-044 

8-848 

9-652 

27 

4-159 

5-199 

6-066 

6-932 

7-799 

8-666 

9-532 

10-399 

28     , 

4-477 

5-596 

6-529 

7'462 

8-395 

9-328 

10261 

11-193 

29 

4-805 

6-006 

7-007 

8-008 

9-009* 

10-01 

11-011 

12-012 

30 

5-141 

6-426 

7-497 

8-568 

9-639 

10-71 

11-781 

12-852 

31 

5-486 

6-865 

8-001 

9-144 

10-237 

11-43 

12-573 

13-716 

32 

5-846 

7-308 

8-526. 

9-744 

10-962 

12-18 

13--398 

14616 

33 

6-216 

7-770 

9-065 

10-360 

11-655 

12-959 

14.-245 

15-54 

34 

6-59 

8-238 

9-611 

10-984 

12-357 

13-73 

15103 

16;476 

35 

6-993 

8-742 

10-199 

11-656 

13-113 

14-57 

16-027 

17-434 

36 

"7-401 

9-252 

10-734 

12-336 

13-878 

15-42 

16-962. 

18-50} 

37 

7-819 

9-774 

11-403 

13-032 

14-861 

16-29 

17-519 

19-543 

33 

8-246 

1(7-508 

12-026 

13-744 

15-462 

17'18 

18-898 

20-61.6 

39 

8-618 

10-86 

12-67 

14-48 

16-29 

18-1 

19-91 

21-61   . 

40 

9-139 

11-424 

13-323 

15-232. 

17-136 

19-04 

20-94.4 

22-843 

41 

9-604 

12-006 

14-007 

16-008 

18-009 

20-00 

22-011 

24-012 

42 

10-065 

12-594 

14-693 

16-792 

18-901 

20-99 

23-089 

25-188 

43 

10-56 

13-20 

15  :4 

17-6 

19-8 

22-00 

242 

26-4 

44 

11-046 

13-818 

16-121 

18-424 

20-727 

23-03 

25-333 

27-636 

45 

11-563 

14-454 

16-863 

19-272 

21-681 

24-09 

26S399 

28-908 

46 

12-086 

15128 

17«626 

20-144 

22-662 

25-18 

27-698 

30<216 

47 

12-614 

15-768 

18-396 

21024 

23-652 

26-28 

28-908 

31-536 

48 

12-816 

16-446 

19-187 

21-928 

24-669 

27-41 

30-151 

32-152 

49 

12-933 

17-142 

19-999 

22-856 

25-713 

28-57 

33-427 

34-2B4 

60 

14-28 

17-85 

20-825 

23-8 

26-775 

29-75 

32-725 

35'7 

NOTE.  —  Mean  effective  pressure  =^Mean  prewure  minus  the  back  preasur* 


HANDBOOK    ON    ENGINEERING. 


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HANDBOOK   ON    ENGINEERING. 


TABLE  NO.  40. 
ROCK  DRILLS. 

Factor  lor  Deter  mi  nine:  Free  Air  Per  Minute  Required  for  Rock  BYills 
at   30,  7O,  80,  00,  1OO   Pounds   Pressure,   and   Altitudes   frditu  Sea 


Level  to  10,000  Feet  Above. 

i 

FACTOR  OF  MULTIPLICATION. 

ALTITUDE  IN 

ATMOSPHERIC 

PRESSURE  AT  DRILL 

FEET  ABoVB 

PRESSURE   LBS. 

SEA  LEVEL. 

FEU  SQlt.  IN 

60  Ibs. 

70  Ibs. 

80  Ibs. 

90  Ibs. 

100  Ibs. 

0 

14.7 

.00 

.133 

2P. 

.40 

.535 

600 

14.46 

.015 

.15 

.28 

.4-25 

.663 

1,000 

14.12 

.03  „ 

.17 

31 

43 

59 

1,500 

13  92 

048 

19 

.33 

,48 

62 

2,000 

13.61 

06 

.21 

.35 

.50 

.645 

3,000 

13.10 

10 

.25 

.40 

.55 

70 

4,000 

12.61 

131 

.287 

.443 

60 

755 

5,000 

12  15 

17 

33 

4J6 

:652 

81 

6,000 

11  75 

.20 

37 

.537 

.705 

1.87 

7,000 

11  27 

.24 

42 

69 

.76 

1.935. 

8,000 

10  85 

.282 

1.4H6 

.<45 

.825 

2.00 

9,010 

10  45 

1  32 

1  51 

1  70 

1.90 

2  07 

10,000 

10.10 

1  365 

1  56 

1.755 

1.963 

2.143 

. 

TABLE  NO.  47. 

Oubic  Feet  of  Air  Per  Minute  Required  to  Operate  a  Small  Number  of 
Rand  Drills  of  Various  Sizes  at  60  Pounds  Air  Pressure  at  Sea 
Level. 


No.  OK  NAME. 

KID. 

No.  1 

Xo  2 

No.  3 

No.  3$ 

No.  4 

No.  6. 

No.  7 

DIam  of  Cylinder 
in  Inches. 

JJin. 

2iin 

2|ln. 

3J  in. 

3J  In. 

3|  In. 

4*ln. 

5  In. 

Number  of  Drills. 

1 

35 

53 

64 

95 

103 

112 

132 

164 

2 

61 

93 

112 

166 

180 

196 

231 

.270 

3 

88 

133 

160 

238 

258 

280 

330 

385 

Otf   ENGINEERING.  93S 

TABLE  47. 

TABLE  OF  THE  ARRAS  OF  CIRCULAR  SKGMKNTS  FOR  DIAMETKR  =  1. 


Height 

Area. 

Height. 

Area   1 

Height  | 

Area. 

Height 

Area 

.001 

000  042 

.064 

.021  168 

1-27 

.Oo7  991 

.190 

103  900 

.002 

.000  119 

oes 

021  660 

128 

058  658 

.191 

.104  6f>- 

.003 

.000  219 

.066 

022  155 

129 

.059  328 

.192 

105  472' 

.004 

.000  337 

.067 

.022  653 

.130 

.059  999 

.193 

.10»;  261 

.005 

.000  471 

.068 

.023  155 

.131 

.OhO  673 

.194 

.107  OM 

.006 

.000  619 

.069 

.023  660 

132 

.061  349 

.195 

.107  843 

.007 

.000  779 

.070 

.024  168 

.133 

06-2  027 

.196 

.108  636 

.008 

.000  952 

.071 

.024  680 

134 

0«2'  707 

.197 

.109  4X1 

.009 

.001  136 

.072 

025  1% 

.135 

063  389 

.198 

110  227 

.010 

.001  329 

.073 

.023  714 

.136 

064  074 

.199 

.111  025 

.011 

.001  533 

.074 

.026  236 

.137 

.064  761 

.200 

111  824 

.012 

.001  746 

.075 

.026  761 

138 

.065  449 

.201 

.112  625 

.013 

.001  969 

076 

.027  290 

.139 

066  140 

.202 

.113  427 

.014 

.002  199 

077 

.027  821 

.140 

.066  833 

.203 

.114  231 

.016 

.002  438 

.078 

.028  35H 

.141 

.«67  528 

.204 

.115  036 

.016 

.002  685 

.079 

.028  894 

.142 

.068  225 

.205 

.115  842 

.017 

.002  940 

.080 

.029  436 

.143 

068  924 

.206 

.116  651 

.018 

.003  202 

.081 

.029  979 

.144 

.069  626 

.207 

.117  460 

.019 

.003  472 

.082 

.030  526 

.145 

.070  329 

.208 

.118  271 

.020 

OOS  749 

.083 

.031  077 

.146 

.071  034 

.209 

.119  084 

.021 

.004  032 

.084 

.031  630 

.147 

.071  741 

.210 

.119  898 

.022 

.004  322 

.086 

.032  186 

.148 

.072  460 

.211 

.120  713 

.023 

.004  619 

.086 

.032  746 

.149 

.073  162 

212 

.121  530 

.024 

.004  922 

.087 

,033  308 

.150 

.073  875 

.213 

.122  348 

.0-25 

.005  231 

.088 

.033  «73 

.151 

.074  590 

.214 

.123  167 

.026 

.005  546 

.089 

.034  441 

.152 

.075  307 

.215 

.123  988 

.027 

.005  «67 

.090 

.035  012 

.153 

.076  026 

.216 

.124  811 

.028 

.006  194 

.091 

.035  586 

.154 

.076  747 

.217 

.125  634 

.029 

.006  527 

.092 

.036  162 

,.155 

.077  470 

.218 

1-26  459 

.030 

008  866 

.093 

.036  742 

.156 

.078  194 

.219 

.127  286 

.031 

.007  209 

.094 

.037  324 

.167 

.078  921 

.220 

.128  114 

.032 

007  559 

.09-> 

.037  909 

Jf»8 

.079  650 

.221 

.128  943 

.033 

.007  913 

.096 

.038  497 

.159 

.080  380 

.222 

.129  773 

.034 

.008  27.i 

.097 

.039  087 

.160 

.081  112 

.223 

.130  605 

.035 

.008  638 

.098 

.039  681 

.161 

.081  847 

.224 

.131  438 

.036 

.009  008 

.099 

.040  277 

.162 

.082  582 

!225 

.132  273 

.037 

.009  383 

.100 

040  875 

.163 

.083  320 

.226 

.133  10(1 

.038 

009  764 

.101 

.041  477 

164 

.084  060 

.227 

.133  946 

.039 

.010  148 

.102 

.042  081 

,165 

.084  801 

228 

.134  784 

.040 

.010  538 

.103 

.042  687 

?166 

.085  545 

.229 

.135  624 

.041 

.010  932 

.104 

.043  296 

167 

.086  290 

.230 

.136  465 

.042 

.011  331 

.105 

.043  908 

168 

.087  037 

.231 

.137  »07 

.043 

.011  734 

.106 

.044  523 

.169 

.087  785 

.232 

.138  151 

.044 

.012  142 

.107 

.045  140 

.170 

.088  53IJ 

.233 

.138  996 

.045 

012  555 

.108 

.045  759 

.171 

.089  -288 

.234 

.139  842 

.046 

.012  971 

.109 

.046  381 

.172 

.090  042 

.235 

.140  689 

.047 

.013  393 

.110 

.047  006 

.173 

.090  797 

.236 

.141  -538 

.048 

.013  818 

.111 

.047  633 

.174 

.091  555 

.237 

.142  388 

.049 

.014  248 

.112 

.048  262 

.175 

.092  314 

.238 

.143  239 

.050 

.014  681 

.113 

.048  894 

176 

.093  074 

.239 

.144  o'.U 

.051 

.015  119 

.114 

.049  529 

.177 

.093  837 

.240 

144  945 

.052 

.015  561 

.115 

.050  165 

.178 

.094  601 

.241 

.145  800 

.053 

.016  008 

.116 

.050  805 

.179 

.095  367 

..242 

.146  656 

.054 

.016  458 

.117 

.051  446 

180 

.096  135 

.243 

.147  513 

.055 

.016  912 

.118 

.052  090 

.181 

096  904  ' 

.244 

.148  371 

.056 

.017  369 

.119 

.062  737 

.182 

097  675 

.245 

.149  231 

.057 

.017  831 

.120 

.053  385 

.183 

.098  447 

.246 

.150  091 

.058 

.018  297 

.121 

.054  037  i 

.184 

.099  221 

.247 

.150  95  3 

.059 

.018  766 

.122 

.054  690 

.1S5 

.099  997 

.248 

.151  816 

.060 

.019  239 

.123 

.055  346 

.186 

100  774 

.249 

.152  681 

.061 

.019  716 

.124 

.056  004 

.187 

.101  553 

.250 

.153  546 

.062 

.020  197 

.125 

056  664 

.188 

.102  334 



,063 

.020  6S1 

.126 

.057  327 

.189 

.103  116 

936  SAKdBddS   Off  ENGINEERING. 

TABLE  47.  -  COM  tinned. 

TABLE   OF   THE   AREAS   OF   CIRCULAR  SEGMENTS   FOft  DtAMKffe  ft  S=  I. 


Height 

Area 

Height 

Area. 

[Height 

Area. 

Height 

Area. 

.251 

.154  413 

.314 

.'.Ill  083 

.377 

.270  951 

.440 

.332  S4* 

.262 

.165  281 

.315 

.212  Oil 

.378 

.271  921 

.441 

*333  836 

.953 

.156  149 

.316 

.212  941 

.  .379 

.272  891 

.442 

.334  829 

.254 

.167  019 

.317 

.213  871 

.380 

.273  861 

.443 

.335  823 

.266 

.W7  €91 

.318 

.214  802 

.381 

.274  832 

.444 

.336  816 

.266 

.158  763 

.319 

.215  734 

.382 

.275  804 

.445 

.337  810 

.267 

.159  636 

.320 

.2  IK  666 

.383 

.276  776 

.446 

.338  809 

.2*8 

.160  511 

.321 

.217  600 

.384 

.277  748 

.447 

.339  799 

.269 

.161  386 

.322 

.218  534 

.385 

.278  721 

.448 

.340  793 

.260 

.162  263 

.323 

.219  469 

.386 

.279  695 

.449 

.341  788 

.261 

.163  141 

.324 

.220  404 

.3S7 

.280  669 

.450 

.342  783 

//2 

.164  020 

.325 

.221  341 

.388 

.281  643 

.451 

.343  778 

.263 

.164  900 

.326 

.222  278 

.389 

,282  618 

.452 

.344  773 

,264 

.165  781 

.327 

.223  216 

,390 

.283  593 

.453 

.345  768 

.265 

.166  663 

.328 

.224  154 

'  .391 

284  569 

.454 

.346  764 

,.266 

.167  546 

.329 

.225  094 

.392 

.285  545 

.455 

.347  760 

.267 

.168  431 

.330 

.226  034 

.893 

.286  521 

.456 

.348  756 

.268 

.169  316 

,3ol 

.226  974 

.394 

.'267  499 

.457 

.349.  752 

.269 

.170  22 

.332 

.227  916 

.395 

.288  476 

.458 

.360  749 

,270 

.171  OHO 

.333 

223  858 

.396 

.289  454 

.459 

.351  745 

271 

.171  978 

.334 

.229  801 

.397 

.290  43-2 

.460 

.352  74» 

.272 

.172  868 

.335 

.230  745 

.398 

.291  411 

.461 

.353  739 

.278 

.1?3  758 

.336 

.231  689 

.399 

292  390 

.462 

.354  736 

,274 

.174  650 

.337 

.232  634 

.400 

.293  370 

.463 

.355  733 

,275 

.175  542 

.338 

.2*3  580* 

.401 

.294  350 

.464 

.356  730 

.276 

.176  436 

.339 

.234  526 

.402 

.295  350 

.465 

.357  7-28 

;277 

.177  330 

.340 

.235  473 

.403 

.296  311 

.466 

.358  725 

.278 

.178  226 

.341 

.236  421 

.404 

.297  292 

.467 

.3.9  723 

.279 

.179  122 

.342 

.237  369 

.405 

.298  274 

.468 

.360  721 

,280 

.180  020 

.343 

.238  319 

.406 

.299  256 

.469 

.361  719 

.281 

.180  918 

.344 

.239  268 

.407 

.300  238 

.470 

.362  717 

,282 

.181  818 

.345 

.240  219 

.408 

.301  221 

.471 

.363  715 

.'/83 

.182  718 

.346 

.241  170 

.409 

.302  204 

.472 

.364  714 

.284 

.183  619 

.347 

.242  122 

.410 

.303  187 

.473 

.365  712 

w285 

.184  622 

.348 

.243  074 

.411 

.304  171 

.474 

.366  711 

*286 

.1*5  426 

.349 

.244  027 

.412 

.306  156 

.475 

.367  710 

,287 

.186  329 

'.650 

.244  980 

.413 

.3<>6  140 

.476 

.368  708 

.288 

.187  235 

.351 

.245  935 

.414 

.307  125 

.477 

.369  707 

*289 

.188  141 

'.352 

.246  890 

.416 

.308  110 

.478 

.370  7ufi 

'.290 

.189  048 

;353 

.247  845 

.416 

.309  096 

.479 

.871  705 

.291 

.189  956 

.354 

.248  801 

.417 

.310  082 

.480 

.372  704 

.292 

.190  865 

.355 

.249  758 

.418 

.311  068 

.481 

.373  704 

>293 

.191  774 

.356 

.250  715 

.419 

.312  065 

.482 

.374  703 

/.294 

.192  685 

.357 

.251  673 

.420 

.313  042 

.483 

.376  7o2 

',295 

.193  597 

.368 

.252  632 

.421 

.314  029 

.484 

.376  702 

»296 

.194  509 

.359 

.253  691 

.422 

.316  017 

.485 

.377  701 

,297 

.195  423 

.360 

.254  551 

.423 

.316  OG5 

.486 

.378  701 

:298 

.196  337 

.361 

.256  511 

.424 

.316  993 

.487 

.379  701 

,299 

.197.  252 

.362 

.256  472 

.425 

.317  981 

.488 

.380  700 

.300 

.198  168 

.363 

.257  433 

.426 

.318  970 

.489 

.381  700 

301 

.199  085 

.364 

.258  395 

.427 

.319  959 

.490 

.382  700 

..302 

.200  003 

.365 

.259  358 

.428 

.320  949 

.491 

.383  700 

^303 

.200  922 

.366 

.260  321 

.429 

.321  938 

.492 

.384  699 

.304 

.201  841 

.367 

.261  285 

.430 

.322  928 

.493 

.385  699 

,305 

.202  762 

.368 

.262  249 

.431 

.323  919 

.494 

.386  699 

.,306 

.203  683 

.3«9 

.263  214 

.432 

.324  909 

.495 

.387  699 

.307 

.204  605 

.370 

.264  179 

.433 

.325  900 

.496 

.388  6<)9 

.308 

.206  528 

.371 

.265  145 

.434 

.326  891 

.497 

.3S9  6«.«9 

.309 

.206  452 

.372 

.266  111 

.435 

.327  883 

.498 

.390  699 

.810 

.207  376 

.373 

.267  078 

.436 

.328  874 

.499 

.391  tt'.'9 

.an 

.208  302 

.374 

.268  046 

.437 

.329  866 

.600 

.392  699 

,312 

.209  228 

.375 

.269  014 

.438 

.330  868 

.313 

.210  155 

..376  1 

.269  982 

.439 

.331  851 



HANDBOOK   ON   ENGINEERING. 


937 


HARTFORD  SPECIFICATIONS; 

The  following  are  the  specffications,  for  steel  plate,  of  the  Hartford  Steam 
Boiler  Inspection  and  Insurance  Co. 

OPEN   HEARTH   FIRE  BOX  STEEL 

To  have  a  tensile  strength  of.  not  less  than  55,000  lbs.,nor  more  than  62,000 
IDS.  per  square  inch  of  section,  with  not  less  than  56% of  ductility  as  indicated 
by  contraction  of  area  at  point  of  fracture  under  test  and  by  an  elongation 
of  25£  in  a  length  of  8  inches. 

HE  ADS- To  be  made  of  best  Open  Hearth  Flange  Steel,  60,000  T.  S.  All 
plates,  both  of  shell  and  heads,  must  be  plainly  stamped  with  name  of 
maker,  brand  and  tensile  strength;  brands  so  located  that  they  may  be  seen 
on  each  plate  after  bolter  is  finished.  Each  shell  plate  must  bear  a  coupon 
which  shall  be  sheared  off,  finished  up  and  tested  by  the  maker  of  ihe 
boiler,  at  his  own  expense.  Each  coupon  must  fill  the  above  requirements 
as  to  strength  and  ductility,  and  must  also  stand  bending  down  double 
when  cold,  when  red  hot  and  after  being  heated  red  hot  and  quenched  in 
cold  water,  without  SILTS  of  fracture.  All  plates  failing  to  pass  these  tests 
will  be  rejected.  All  tests  and  inspections  of  material  shall  be  made  at  the 
place  of  manufacture  prior,  to  shipment. 

TABLE  No.  48. 

Showing  details  of  rivet  laps  for  different  thicknesses  of  boiler  plate  as  ad- 
vocated by  the  Hartford  Steam  Boiler  Inspection  and  Insurance  Co.  for 

DOUBLE   RIVETED    BUTT   JOINTS. 


2*4X4* 


ofi 

if 


4V»  in 


il" 


9     in 


1014  •' 
11J4  " 


H  in 

ft:: 


ir 


ill- 


IK  in2K  In 
.  -    - 


2H' 
2M 

2^ 


TABLE  No.  48.— Continued. 
TRIPLE  RIVETED  BUTT  JOINTS. 


Thicknes 
Plate. 


iame 
Riv 


Pitch  of  Riv 
in  inches. 


Width  o 
Outside  B 
Strap. 


idth  of 
ide  Bu 
Strap. 


Thickne 
Coveri 
Stra 


sg. 

Ill 
& 


n 

si 
53 

s~ 


J°s 
^3s 

O  S3  «>* 

C3*3  * 

®O  <»CC 

&D       >• 

|w 


i 


y 


3|x6| 
3ix7 


11§  in 


ij 


p 

2il 


23 


11  in 


87.5^ 

86% 

88% 

88% 

87.59J 

87.6^ 


86.6% 


For  detailed  drawings  of  above  laps,  tee  pages  946  to  951  inclusive. 


938 


HANDBOOK   ON   ENGINEERING. 


STAYING  BOILER  HEADS. 

In  the  return  tubular  boiler  the  tubes  occupy  a  considerable 
portion  of  the  boiler  head,  usually  amounting  to  about  two-thirds 
of  the  entire  area  of  the  head,  as  shown  by  Figure  403.  There 


•V* 


o 


_  J 


ooooo 
ooooo 
ooooo 
ooooo 
oooo 
o 


ooooo 
ooooo 
ooooo 
ooooo 
oooo 
o 


Fig.  403. 

Showing  No.  of  stays  in  a  well  proportioned  boiler  of  60  in.  in  diameter 

is  very  little  surface,  comparatively  speaking,  between  the  tubes 
for  pressure  to  act  upon,  and  as  the  tubes  serve  as  stays  to  a  con- 


HANDBOOK    ON    ENGINEERING.  939 

siderable  extent,  it  is,  therefore  unnecessary  to  introduce  stays 
between  them.  The  remaining  flat  surface  above  and  below  the 
tubes  is  exposed  to  full  boiler  pressure,  and  would  tend  to  bulge 
outward,  and  thus  loosen  the  tube  ends  if  not  properly  secured 
in  position.  The  upper  part  of  the  head  can  be  held  in  position 
by  means  of  rods  connected  to  both  heads,  or  by  means  of  stays 
connected  to  the  head  and  boiler  shell.  When  the  area  above 
the  tubes  is  secured  by  means  of  rods  connected  to  both  heads, 
the  rods  are  called  direct,  or  through  stays,  and  when  the 
rods  run  from  the  head  to  the  shell,  they  are  called  diagonal 
stays. 

There  is  no  necessity  for  using  direct  or  head-to-head  stays  in 
the  return  tubular  boiler,  because  the  shell  possesses  a  surplus  of 
strength  in  the  direction  of  its  length,  which  is  sufficient  to  resist 
all  the  pressure  that  can  be  brought  to  bear  on  the  area  of  the 
head  above  and  below  the  tubes.  The  ability  of  the  shell  to  aid 
in  strengthening  the  head  can  be  made  use  of  by  putting  in  the 
proper  number  of  diagonal  stays.  The  advantages  offered  by 
the  latter  style  of  stay  are  that  the  stays  occupy  comparatively 
little  space  in  the  steam  room  of  the  boiler,  thus  permitting  the 
interior,  both  above  and  below  the  tubes,  to  be  thoroughly  in- 
spected and  cleaned,  and  the  stays  being  shorter,  the  effects  of 
expansion  are  less  noticeable  upon  the  boiler  heads,  and  the  ten- 
dency of  the  sta}Ts  to  work  loose  is  correspondingly  reduced. 

When  calculating  the  number  of  stays  required  in  a  boiler 
head,  it  is  not  necessary  to  include  the  entire  area  above  the 
tubes,  because  it  has  been  found  by  experiment  that  the  flange 
of  the  head  imparts  sufficient  strength  to  a  distance  of  3  inches 
from  the  flange,  and  that  the  tubes  tend  to  stay  the  head  to  a 
distance  of  2  inches  above  the  tops  of  the  upper  row  of  tubes. 
It  will  be  seen,  therefore,  that  the  actual  area  to  be  stayed  ex- 
tends to  within  3  inches  of  the  shell,  and  to  within  2  inches  of 
the  top  of  the  tube.  The  area  to  be  stayed  is  contained  within 


940 


HANDBOOK    ON    ENGINEERING. 


the  dotted  lines  shown  in  Fig.  404,  and  is  in  the  form  of  a  seg- 
ment of  a  circle. 

In  order  to  find  the  total  pressure  or  stress  on  this  area  it  is 
first  necessery  to  find  the  area  of  the  segment  formed  by  the 
dotted  lines.  It  will  be  seen  that  the  top  of  this  segment  is  an 


i 


oooo 


Fig.  404. 

Showing  the  area  to  be  stayed. 

arc  of  a  circle  which  is  smaller  than  the  boiler  head.  If  we  take 
off  3  inches  from  the  diameter  of  the  head  at  both  top  and  bot- 
tom it  will  give  the  diameter  of  the  circle  of  which  the  segment  is 


HANDBOOK    ON    ENGINEERING.  941 

a  part,  and  the  diameter  will  be  found  to  be  6  inches  less  than 
the  diameter  of  the  boiler  head.  The  distance,  H,  Fig.  404,  is 
called  the  height  of  the  segment.  The  area  of  the  segment 
multiplied  by  the  steam  pressure  gives  the  total  stress  to  be  re- 
sisted by  the  stays,  and  the  total  stress  divided  by  the  stress 
which  one  stay  will  hold  gives  the  number  of  stays  required  .• 

To  illustrate  the  method  of  finding  the  number  of  stays  re- 
quired, suppose  the  stays  in  a  60-inch  and  a  72-inch  boiler  head 
are  to  be  determined.  In  a  well  proportioned  boiler  head  th<* 
distance  from  the  bottom  of  the  shell  to  the  top  of  the  upper  row 
of  tubes  is  about  60  per  cent  of  the  diameter  of  the  head,  and 
60  per  cent  of  60  inches  is  36  inches,  which  is  the  distance,  A, 
Fig.  404.  The  distaace  from  the  top  of  the  tubes  to  the  top  of 
the  boiler  head  is  60  —  36  =  24  inches.  According  to  the  rule 
previously  given  we  must  subtract  the  width  of  the  space,  D, 
which  is  three  inches,  and  also  the  width  of  the  space,  E,  which  is  2 
inches  thus  making  the  height  of  the  segment  equal  to  24 — (3+2) 
=  19  inches,  which  is  the  height,  H,  Fig.  404.  Divide  the 
height,  H,  by  the  diameter,  d,  of  the  circle  of  which  the  segment 
is  a  part.  In  the  table  of  areas  of  segments  of  circles  on 
page  935,  find  the  quotient  in  the  column  headed,  Height, 
and  multiply  the  corresponding  decimal  in  the  column  headed 
area,  by  the  square  of  the  diameter  of  the  circle  of  which 
the  segment  is  a  part ;  the  product  will  be  the  area  of  the 
segment  included  within  the  dotted  lines.  Thus,  the  diam- 
eter of  the  circle  of  which  the  segment  is  a  part  is  60  —  6 
=  54  inches,  and  19  -f-  54  =  .351.  In  the  column  headed 
Height,  we  find  .351  and  opposite  we  find  the  decimal  .2459 
which,  when  multiplied  by  the  square  of  the  diameter  of  the 
circle,  gives  .2459  X  (54  X  54)  =  717  square  inches,  the  area 
of  the  segment.  If  the  boiler  pressure  is  to  be  100  pounds 
on  each  square  inch  the  total  pressure  will  be  717  X  100  = 
71,700  pounds,  which  is  the  stress  to  be  borne  by  all  the  stays. 
When  stays  are  not  subjected  to  the  action  of  water  they  may  be 


942 


HANDBOOK    ON    ENGINEERING. 


allowed  a  stress  of  7,500  pounds  per  square  inch  of  section,  but 
when  subjected  to  the  action  of  the  water  in  the  boiler  the  stress 
should  not  exceed  6,000  pounds. 

Now  stays  in  horizontal  tubular  boilers  are  generally  made  of  1 
inch  round  bars  and  as  a  bar  of  this  size  has  an  area  of  .7854  of 
a  square  inch  each  bar  or  stay  will  stand  a  stress  of  7,500  X 
.7854  =  5890  pounds,  and  the  number  of  stays  required  is 
71,700  ~  5890  =33  12  stays,  as  shown  in  Fig.  403. 

J  K 


Gr 


\i 


Fig.  405. 

Method  of  connecting  a  diagonal  stay. 

The  stress  on  diagonal  stays  is  a  little  greater  than  on  direct 
stays  running  from  head  to  head,  so  that  the  area  of  the  12  stays 
must  be  increased  in  proportion  to  the  increased  stress.  The 
minimum  length  of  stay  allowable  is  3J  feet,  and  the  stress 
on  the  diagonal  stay  is  as  much  greater  than  the  stress  on  the 
direct  stay  as  the  length  of  the  stay  FG,  Fig.  405,  is  greater 
than  the  distance  JK.  Suppose  the  distance,  JK,  is  45  inches, 
and  the  length  of  the  stay,  FG,  48  inches,  then  the  stress  on  the 
diagonal  stay  is  48  -=-  45  =  lTJo-  times  the  stress  on  the  direct 
stay  and  consequently  the  area  of  the  stay  must  be  1T^  times  the 
area  calculated  or  .7854  X  ITTFTF  =  -^  °*  a  S(luare  inch,  which 
corresponds  to  a  diameter  of  l^  inches.  Thus  the  60-inch  boiler 
requires  12  stays  each  1T^  inches  in  diameter,  as  shown  in  Fig.  403. 


HANDBOOK   ON   ENGINEERING.  943 

The  number  of  stays  required  in  the  72-inch  boiler  is  found  in 
the  same  manner.  Thus,  the  diameter  of  the  circle  of  which  the 
segment  to  be  braced  is  a  part,  is  72  —  6  =  66  inches.  The  dis- 
tance from  the  bottom  of  the  shell  to  the  top  of  the  tubes  is  60 
per  cent  of  72  inches,  or  43  inches,  and  the  distance  from  the  top 
of  the  tubes  to  the  top  of  the  shell  is  72  —43—29  inches.  From 
this  is  to  be  subtracted  3  inches  measured  from  the  shell,  and  2 
inches  measured  from  the  tubes,  making  5  inches  in  all,  thus  leav- 
ing 29  —  5  —  24  inches,  which  is  the  height,  H,  of  the  segment 
represented  by  the  dotted  lines.  Dividing  the  height  of  the  seg- 
ment by  the  diameter  of  the  circle  of  which  the  segment  is  a  part,  we 
have  24-r-66=.363.  In  the  table  of  areas  of  segments  of  circles 
find  .363  in  the  column  headed,  Height,  and  opposite  we  find  the 
decimal  .2574,  which,  when  multiplied  by  the  square  of  the 
diameter  of  the  circle  of  which  the  segment  is  a  part,  gives 
.2574  X  (  66  X  66  )  =  1121  square  inches  area  of  segment. 
Assume  the  pressure  to  be  110  pounds  per  square  inch.  The 
total  stress  to  be  borne  by  all  the  stays  is  1121  X  HO  =  123,310 
pounds.  If  the  stays  are  to  be  of  1  inch  rods,  which  is  the 
smallest  size  used  for  boilers  above  44  inches  in  diameter,  the 
area  of  each  rod  or  stay  will  be  .7854  of  a  square  inch,  and  it 
will  be  capable  of  resisting  a  stress  of  7,500  X  .7854  =  5890 
pounds. 

The  number  of  1  inch  stays  required,  therefore,  is  123,310  -5- 
5890=21  stays. 

Now,  if  the  distance,  J  K,  Fig.  405,  in  this  case  is  48  inches, 
and  the  length  of  the  stay  52  inches,  the  stress  on  the  diagonal 
stay  will  be  52  ~-  48  =  1T§ ^  times  what  it  would  be  on  a  direct 
stay,  and  consequently  the  area  of  the  stay  must  be  lyf^  times 
greater,  or  .7854  X  1.08  =  .85  square  inch,  which  corresponds 
to  a  diameter  of  l^  inches,  therefore  the  72-inch  boiler  will 
require  2 1  stays  1-^  inches  in  diameter. 

It  sometimes  happens  that  the  maximum  pressure   employed 


944 


HANDBOOK   ON   ENGINEERING. 


when  calculating  stays  call  for  a  certain  number  which  it  is  found 
difficult  to  properly  distribute  over  the  boiler  head.  In  this  case 
the  number  of  stays  must  be  changed,  but  the  combined  area  of 
the  stays  must  necessarily  remain  the  same.  To  illustrate,  sup- 


oooooo 
ocoooo 
oooooo 
oooooo 
oooooo 
ooooo 

00 


oooooo 
oooooo 
oooooo 
oooooo 
oooooo 
ooooo 
oo 


Fig*  406. 

No.  of  stays  in  a  well  proportioned  boiler  of  72  in.  in  diameter. 

pose  21  stays  could  not  be  distributed  to  advantage  on  the 
72-inch  head,  and  it  is  desired  to  use,  say,  18  stays.  Now,  the 
21  stays  have  a  combined  area  of  .85  X  21  =  17J  square  inches, 
and  this  area  divided  among  18  stays  would  give  each  an  area  of 


HANDBOOK    ON    ENGINEERING.  945 

17|  -f-  18  =  1  square  inch,  which  corresponds  to  a  diameter  of 
1|  inches,  therefore  the  72-inch  boiler  will  require  18  stays  1£ 
inches  in  diameter. 

The  same  method  is  used  when  finding  the  number  and  size  of 
the  stays  below  the  tubes.  It  is  seldom  practicable,  with  the 
usual  arrangement  of  tubes  and  man -hole,  to  use  more  than  two 
stays  below  the  tubes  so  that  the  area  is  made  sufficient  to  enable 
two  stays  to  carry  the  stress. 

When  finding  the  size  and  number  of  screw  stays  or  stay 
bolts,  such  are  used  in  the  water-legs  of  locomotive  boilers  and 
in  the  headers  of  water  tube  boilers  where  the  bolts  are  subjected 
to  the  action  of  the  water,  the  maximum  stress  allowable  per 
square  inch  of  net  section,  which  is  the  area  of  the  bolt  measured 
at  the  bottom  of  the  threads,  is  6,000  pounds.  For  instance, 
what  is  the  diameter,  number  and  stress  on  the  stay  bolts  required 
in  the  water-leg  of  a  locomotive  boiler,  the  flat  surface  measuring 
40  X  54  inches,  and  the  maximum  pressure  125  pounds?  The 
total  area  is  found  to  be  40  X  54  =  2,160  square  inches,  and  the 
total  pressure  to  be  resisted  by  the  stay  bolts  is  2,160  X  125  = 
270,000  pounds,  For  pressures  exceeding  100  pounds  per 
square  inch,  the  pitch  of  staybolts  in  stationary  boilers  should 
not  exceed  4J  inches.  .  The  area  supported  by  each  bolt  is 
4J  X  4J  =  18  square  inches  and  the  stress  on  each  bolt  is 
18  X  125  =  2,250  pounds.  The  total  stress  is  270, 000  pounds, 
consequently  270,000  divided  by  2,250  will  give  the  number  of 
bolts  which  is  270,000  -~  2,250  =  120.  The  stress  allowed  per 
square  inch  of  net  sectional  area  is  6,000  pounds,  and  as  each 
bolt  must  sustain  a  stress  of  2,250  pounds  the  net  area  of  each 
bolt  is  2,250  -f-  6,000  =  .375  or  f  of  a  square  inch  measured  at 
the  bottom  of  the  threads,  which  corresponds  to  a  bolt  f  inch  in 
diameter  measured  to  outside  of  threads.  This  surface,  there- 
fore, requires  120  staybolts  -if  inch  in  diameter,  spaced  4J  inches 
between  centers  for  a  working  pressure  of  125  pounds. 


946 


HANDBOOK    ON    ENGINEERING. 


DOUBLE   RIVETED   LAP  AND   GIRTH   JOINT'S 

Longitudinally  Riveted.) 

This  construction  is  based  on  a  tensile  strength  of  60,000  Ibs.  for  plata 
.and  a  shearing  strength  of  38,000  Ibs.  for  rivets. 


LAP  JOINT. 


GIRTH  JOINT. 


-23- 


•  plates,  double  riveted;  holes,  %•;  rivets,  J|".    (Efficiency , 


LAP  JOINT. 


GIRTH  JOINT. 


plates,  double  riveted;  holes.  U','  rivets,  fc%    (Efficiency, 
59 


HANDBOOK    ON    ENGINEERING. 


947 


Double  Riveted  Lap  and  Girth  Joints. 

LAP  JOIKT.  GIRTH  JOIHT. 

-34* 


•  plate*,  doable  riveted ;  holes, }}•  i  rivets,  £ -.    (Efficiency .  TO*.  ) 


GIKTH  JOINT. 


•ai- 


'  plates,  double  riveted;  hole*  I';  rlrets,  H*-   (Efficiency,  TOjt) 


OIBTB  JOINT. 


(I*  plat**  double  rtreted)  hol««,  1  A' »  rtvet*  1 '     (Efficiency, 


948 


HANDBOOK 


Triple  fciveted  Lap  and  Girth  Joints. 

(Longitudinally  Riveted  ) 
This  construction  is  based  on  a  tensile  strength  of  60.000  Ibs,  for  plate 


ittfra  shearing  strength  of  88,000  Ibs.  for  rivets. 


IiAP  JOINT.. 


GIRTH  JOINT. 


'  plates,  triple  riveted)  holes,  }j-i  rivets,  %•.    (Efficiency.  77i.) 


LAP  JOINT. 

k — 3k*  — 


GIRTH  JOINT. 


CM 

i*o 


b*  plmtes.  triple  riveted;  holes,  %  *  $  rivets.  14-.   (Efficiency,  76*.) 


HANDBOOK    ON    ENGINEERING. 

rtAP~  JOINT.  GIRTH  JOIKT. 

K 3*'- 


'  plates,  triple  riveted ;  holes,  {|* ;  rivets  2£ '.    (Efficiency,  755?.) 


LAP  JOIKT. 


GIRTH  JOINT. 


1» 

«SJ 

f 


'  plates,  triple  riveted;  boles,  18';  rivets,  %•»    (Efficiency .75*.) 


GIRTH  JOINT. 


I — a*:- 


plates,  triple  riveted ;  holes,  I  • ;  rivets,  if 


949 


950 


HANDBOOK    ON    ENGINEERING, 


Triple  Riveted  Butt  Joints. 


nt  for  &•  plates;  holes,  &';  rivets,  ||».    (Efficiency,  88*.) 

i 


^ 


0 


•^> 


f^ 


ffl 


feutt  joint  for  %•  plates;  holes,  y ;  rivets,  &'.    (Efficiency. 


Butt  joint  f  or  /e •  plates;  holes,  53 ;  •  rlvete,  %'.    (Efficiency,  86*.) 


HANDBOOK   ON    ENGINEERING. 
TRIPLE  RIVETER  BUTT  JOINTS-CContinued.) 


ck. 


Butt  joint  for  Vs"  plates;  holes,  1";  rivets,  Jg'    (Efficiency,  86.65?.) 


i 


Butt  joint  for  ft*  plates;  holes,  1^' ;  rivets,  1%    (Efficiency,  66£) 


Butt  Joint  tor-K*  nl»tew   t»J««.  I.A'  ri»et»  f.  (Efficiency.  8C*.} 


951 


952 


HANDBOOK   ON   ENGINEERING. 


£S8SSgS5&S8gS885Sgi&58Sgg55o 

Thickness  of  material 
required. 

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Diameter  of  flues. 

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HANDBOOK    ON    ENGINEERING. 


953 


Greatest  length  of  sections  allowable,  30  inches. 

J2 
3 

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954  HANDBOOK    ON    ENGINEERING. 


CHAPTER    XXXI. 
HYDRAULIC  ELEVATORS. 

The  purpose  of  these  pages  is  to  furnish  such  instruction  and 
information  as  will  be  of  use  to  engineers  in  the  care  of  elevator 
machinery.  To  accomplish  this  end,  cuts  and  sectional  views 
of  cylinders  and  valves  of  the  different  types  of  elevator  ma- 
chinery made  by  the  different  elevator  companies,  are  herein  pro- 
duced, so  as  to  make  the  different  elevators  plain  to  the  engineer. 
It  must  be  borne  in  mind  that  the  one  point  of  paramount  im- 
portance for  the  successful  operation  of  an  elevator  is  proper 
care  and  management ;  a  lack  of  thorough  knowledge  of  the  ma- 
chine and  lack  of  attention  in  this  respect  shortens  the  life  of  the 
machine  and  often  makes  extensive  repairs  necessary. 

Hydraulic  elevators  are  designated  as  horizontal  or  vertical 
according  to  the  position  in  which  the  lifting  cylinder  is  placed. 
Horizontal  machines  are  generally  placed  in  buildings  where 
there  is  ample  floor  space,  while  vertical  elevators  are  used  in 
buildings  standing  on  small  lots.  Vertical  elevators  are  made  so 
as  to  lift  the  elevator  by  means  of  ropes,  and  are  geared  up  so 
that  the  travel  of  the  piston  is  considerably  less  than  that  of  the 
car,  and  they  are  also  made  so  that  the  piston,  or  plunger,  pushes 
directly  against  the  bottom  of  the  car  and  lifts  it  to  the  top  of 
the  building.  This  type  of  elevator,  which  is  now  being  intro- 
dued  on  an  extensive  scale,  is  known  as  the  direct  plunger,  or 
simply  plunger  elevator. 

Horizontal  hydraulic  elevators  are  designated  as  pushing  or 
pulling  machines  according  to  the  way  in  which  the  power  is  ap- 
plied. In  pulling  machines,  the  water  under  pressure  is  admit- 


HANDBOOK    ON   ENGINEERING. 


955 


ted  between  the  piston  and  the   front   end   of  the   cylinder,  and 
the  piston  rods  pull   a  set  of  movable  sheaves   toward  the   cylin- 


'/*    / 


/ 


Fig.  407.    Horizontal  Hydraulic  Elevator.    Pushing  Type. 


956  HANDBOOK    ON    ENGINEERING. 

der,  aud  thus  lift  the  car.  In  pushing  machines  the  water  is 
admitted  to  the  back  end  of  the  cylinder  and  the  piston  rod  pushes 
the  movable  sheaves  away  from  the  cylinder  to  lift  the  elevator 
car. 

The  general  arrangement  of  a  horizontal  hydraulic  elevator  of 
the  pushing  type  is  shown  in  Fig.  407.  This  is  an  Otis  machine. 
The  lifting  cylinder  is  at  A,  B  being  the  piston  rod,  C  the  set  of 
movable  sheaves  and  D  a  set  of  stationary  sheaves.  The  lifting 
ropes  pass  around  these  two  sets  of  sheaves  several  times,  block 
and  tackle  fashion,  and  then  run  up  and  over  an  overhead  sheave 
E  and  down  to  the  top  of  the  elevator  car.  Another  set  of  ropes 
run  up  over  the  sheave  F  and  down  to  a  counterbalance  weight  G. 
The  number  of  times  that  the  lifting  ropes  wind  around  the 
sheaves  determines  the  gear  of  the  machine.  The  gear  is  always 
the  ratio  between  the  distance  traveled  by  the  car  and  the  stroke 
of  the  piston.  If  the  car  runs  ten  times  the  stroke  of  the  piston, 
the  gear  is  ten  to  one,  and  so  on  for  any  other  ratio.  Horizontal 
machines  are  geared  from  six  up  to  14  to  one,  the  average  being 
about  10  and  12. 

The  valve  for  operating  the  elevator  is  at  jET,  and  is  of  the  same 
design  as  that  used  by  the  same  makers  for  their  vertical  ma. 
chines  and  is  explained  in  connection  with  the  latter  machines. 
Another  valve  is  located  at  /  and  its  office  is  to  stop  the  elevator 
automatically  at  the  top  and  bottom  landings,  if  the  operator  fails 
to  move  the  operating  lever.  This  valve  is  actuated  by  the  chain 
J  which  is  moved  by  an  arm  K  attached  to  the  movable  sheave 
frame.  This  arm  strikes  stop  balls  that  are  secured  to  J  at  the 
proper  points  to  cause  the  car  to  stop  even  with  the  top  and  bot- 
tom landings  of  the  building. 

This  illustration  shows  an  actuating  lever  L  in  the  car,  which 
acts  through  a  system  of  rope  connections  to  move  the  valve  H. 
This  arrangement  is  used  for  high  speed  passenger  elevators,  but 


HANDBOOK    ON   ENGINEERING. 


957 


slow  speed  freight  machines  are  generally  arranged  so  that  a 
hand  rope  passes  through  the  car  and  the  valve  is  moved  by 
pulling  on  this  rope.  The  rope  connections  between  the  lever  L 


Fig.  408.    Horizontal  Hydraulic  Elevator  Machine. 

and  the  valve  are  generally  arranged  on  one  of  two  different  sys- 
tems, which  are  designated  as  the  running  rope  and  the  standing 
rope.  In  the  former  the  ends  of  the  ropes  are  fastened  to  the 
ends  of  a  cross-lever  located  on  the  back  end  of  the  shaft  that 
carries  L  and  therefore  run  when  the  car  runs.  In  the  standing 
rope  system  the  ends  of  the  ropes  are  secured  to  the  top  and  the 
bottom  of  the  elevator  well  and  therefore  stand  still  when  the  car 
runs.  In  Fig.  407  it  will  be  seen  that  there  are  small  sheaves  n', 
ft,  at  top  and  bottom  of  the  elevator  well,  the  latter  being  mounted 
on  the  side  of  a  larger  sheave  over  which  runs  a  rope  0.  This 
rope  passes  around  a  sheave  P  located  on  the  valve  casing,  and 
by  its  rotation  the  valve  is  actuated  in  a  manner  fully  explained 
in  connection  with  vertical  elevators.  The  lever  L  is  connected 
with  the  sheaves  ri ',  ?i,  by  the  ropes  m,  and  by  rocking  i,  to 
one  side  or  the  other,  these  ropes  are  drawn  up  on  one  side  and 
let  out  on  the  other  so  as  to  cause  one  of  the  n  sheaves  to  rise 
and  the  other  to  fall  and  thus  to  rotate  the  large  sheave,  am} 
through  rope  0  the  valve  sheave  P. 


958 


HANDBOOK    ON   ENGINEERING. 


HANBBOOK   ON   ENGINEERING.  959 

Another  design  of  pushing  machine  is  shown  in  perspective  in 
Fig.  408.  This  is  a  Crane  machine,  and  canbe  more  fully  under- 
stood from  Figs.  409-410  the  first  being  a  side  elevation  and  the 
second  a  plan.  Fig.  409  also  serves  to  make  clearer  the  operation 
of  the  running  rope  connection  between  the  car  lever  and  the 
valve.  When  the  operating  valve  is  moved  by  means  of  a  car 
lever,  it  cannot  be  moved  directly,  because  the  lever  swings 
through  a  small  distance  only  and  on  that  account  the  force  re- 
quired to  move  it  would  be  more  than  the  operator  could  exert 
for  any  considerable  length  of  time.  When  the  valve  is  operated 
by  a  hand  rope  passing  through  the  car,  a  small  force  is  required 
to  pull  the  rope  because  it  is  pulled  through  several  feet,  which  is 
four  or  five  times  the  distance  through  which  the  lever  is  moved. 
To  make  the  lever  move  freely  a  small  valve  is  provided,  called  a 
pilot  valve,  and  this  is  what  is  moved  by  the  car  lever.  The  pi- 
lot valve  permits  water  to  flow  in  or  out  of  the  main  valve  in  such 
a  way  as  to  move  it  in  the  desired  direction.  In  Fig.  409  the  pilot 
valve  is  at  M,  and  the  main  valve  is  inside  of  the  chamber  L  L. 
The  automatic  stop  valve  is  within  K,  and  is  actuated  through 
rod  J  by  means  of  the  two  arm  lever  H  G  and  the  frame  F.  This 
frame  has  attached  to  it  a  rod  upon  which  are  fastened  stops  G 
D  and  these  are  struck  by  an  arm  E  projecting  from  the  movable 
sheave  frame,  see  Fig.  410.  In  this  way  valve  Kis  moved  auto- 
matically at  the  top  and  bottom  landings  to  stop  the  elevator. 

The  operation  of  the  main  and  pilot  valves  can  be  understood 
from  Fig.  411  which  is  a  vertical  sectional  view.  The  shaft  8  is 
rotated  by  the  carlever  as  shown  in  Fig.  409.  If  the  movement  is 
such  as  to  swing  A  to  the  left,  the  pilot  valve  at  M  will  be  moved 
in  the  same  direction  and  water  will  pass  from  space  B  at  the 
large  end  of  the  main  valve  to  the  discharge  pipe  C.  This  will 
force  the  valve  to  the  left  and  thus  connect  the  supply  pipe  E 
with  the  cylinder  inlet  D  through  the  movement  to  the  left  of  pis- 
ton Go  The  water  passing  into  the  cylinder  will  force  the  piston 


960 


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m 


be 


HANDBOOK    ON   ENGINEERING. 


961 


out  and  thus  lift  the  elevator.  It  will  be  seen  that  as  soon  as  the 
main  valve  moves  to  the  left,  it  carries  lever  /  with  it,  and  as  this 
ever  swings  around  J  the  pilot  valve  is  moved  back  to  the  stop 
position.  It  can  also  be  seen  that  the  further  the  pilot  valve  is 
moved  by  the  swing  of  A,  the  further  the  main  valve  must  move 
to  swing  I  far  enough  to  return  the  pilot  to  the  stop  position ; 
that  is,  the  further  the  arm  is  moved,  the  wider  the  main  valve  is 
opened.  Thus  the  extent  to  which  the  main  valve  is  opened  is 
dependent  upon  the  angle  through  which  A  swings,  and  this 
angle  is  dependent  on  the  angle  through  which  the  car  lever  L  is 


M 


Fig.  411.    Take  of  Fig.  408  Machine. 

moved ;  hence,  the  operator  has  as  perfect  control  of  the  move- 
ment of  the  main  valve  as  if  he  moved  it  by  pulling  directly  upon 
a  hand  rope. 

Fig*  4f  2  is  a  photographic  view  of  the  Morse  &  Williams  hori- 
zontal pushing  machine.  This  is  what  is  called  a  double  decked 
machine  and  is  a  construction  commonly  resorted  to  when  floor 
space  is  limited.  Each  machine  operates  a  different  elevator. 
The  valve  of  this  machine  is  arranged  to  be  operated  by  a  hand 
rope,  the  latter  being  passed  around  the  large  sheave  wheel  A. 
On  the  shaft  of  this  wheel  is  mounted  a  small  pinion  that  meshes 
into  a  rack  attached  to  the  end  of  the  valve  stem.  This  construc- 
tion will  be  seen  illustrated  fully  and  explained  in  connection  with 


HANDBOOK    ON    ENGINEERING. 


HANDBOOK   ON   ENGINEERING.  963 

the  vertical  elevator  machines.  The  automatic  stop  valve  is  op* 
erated  by  means  of  the  rope  seen  at  the  side  of  the  machine  that 
passes  around  sheaves  J3,  (7,  the  latter  acting  to  close  the  valve. 

HORIZONTAL    HYDRAULIC   ELEVATORS,  PULLING  TYPE. 

In  Fig.  413  is  shown  a  horizontal  machine  of  the  pulling  type. 
This  is  the  design  made  by  the  Whittier  Elevator  Company.  The 
stationary  set  of  sheaves  is  located  at  the  front,  and  the  travel- 
ling sheaves  are  between  it  and  the  end  of  the  cylinder.  The  op- 
erating valve  is  on  top  of  the  cylinder  at  the  front  end,  the  pilot 
valve  being  on  top  of  the  main  valve.  The  automatic  stop  valve 
is  just  below  the  main  valve  and  is  operated  by  means  of  a  rope 
passing  over  sheaves  and  provided  with  stop  balls,  all  of  which  is 
clearly  shown.  The  arrangement  of  the  valve  and  pilot  valve  can 
be  understood  from  Figs.  414-415,  the  first  being  a  plan  and  the 
second  a  vertical  section.  The  pilot  valve  is  moved  by  lever  E 
which  is  connected  with  the  actuating  ropes  A  A  that  run  to  the 
car  lever.  The  lever  E  is  pivoted  at  F  so  that  when  it  swings  in 
either  direction  it  moves  the  pilot  valve  through  rod  C.  The  oper- 
ation of  this  valve  and  pilot  valve  is  the  same  as  that  of  Fig,  411 
that  is,  the  movement  of  the  pilot  valve  to  either  side  of  the  cen- 
tral position  acts  to  connect  the  end  Koi  the  main  valve  cylinder, 
either  with  the  pressure  pipe  P  or  the  exhaust  It,  thus  moving 
the  main  valve  in  one  direction  or  the  other.  If  .ZT  is  connected 
with  the  pressure  pipe,  the  valve  is  moved  to  the  left  and  the 
cylinder  is  connected  with  the  discharge  pipe  and  the  elevator 
runs  down.  The  movement  of  the  pilot  valve  in  the  opposite  di- 
rection will  connect  K  with  the  discharge  and  then  the  main  valve 
will  move  to  the  right  and  the  cylinder  will  be  connected  with  the 
pressure  pipe  and  the  elevater  will  go  up.  In  either  case,  the 
pilot  valve  is  first  moved  in  the  same  direction  in  which  the  main 
valve  is  moved  immediately  after,  and  the  movement  of  the  main 


964 


HANDBOOK   ON    ENGINEERING. 


HANDBOOK    ON    ENGINEERING. 


965 


valve  acts    to  return  the  pilot  to  the  stop  position  through  the 
lever  D  and  rod  C. 

The  automatic  stop  valve  is  shown  in  Figs.  416-417,  the  two 
drawings  being  taken  at  right  angles  to  each  other.  This  valve 
consists  of  two  parts,  the  valve  proper  B  and  a  cylindrical  car- 
rier A.  The  weight  shown  in  Fig.  413  acts  to  swing  A  with  B  into 
the  position  shown  in  Fig.  417,  and  the  automatic  stops  act  to 
swing  these  parts  so  as  to  cover  either  one  of  the  ports  (7,  D.  If 
the  car  is  going  up  the  automatic  stop  rotates  A  in  a  clockwise 
direction  so  as  to  cover  port  C,  and  if  coming  down  the  rotation 


Fig.  414.    Valve  of  Whittle  r  Machine.    Top  View. 

s  opposite,  so  that  A  is  moved  over  D.  The  valve  B  is  held 
against  A  by  the  tension  of  a  spring,  and  also  by  the  water  pres- 
sure, when  the  elevator  is  being  stopped  ;  but  when  it  is  started 
again,  by  reversing  the  position  of  the  main  valve,  the  pressure 
acts  to  lift  B  from  its  seat  against  A  and  permit  water  to  leak 
through  slowly  and  thus  allow  the  car  to  start  up  gradually.  As 
soon  as  the  car  begins  to  move,  the  stop  ball  is  drawn  out  of  the 
way  and  the  weight  acting  on  A  draws  it  into  the  position  of  Fig. 
417  so  as  to  open  the  valve  wide  and  permit  the  car  to  attain  full 
speed. 


966 


HANDBOOK    ON    ENGINEERING. 


VERTICAL  HYDRAULIC  ELEVATORS. 

The  construction  of  a  vertical  elevator  machine,  Otis  type,  can 
be  understood  from  Fig.  418  which  is  a  vertical  elevation  of  the 
lifting  cylinder  and  operating  valve  in  section.  At  A  the  valve 
is  in  the  position  it  takes  when  the  elevator  is  at  rest.  At  B  the 
position  of  the  valve  is  that  corresponding  to  the  up  motion  of 
the  car,  while  at  G  the  position  of  the  valve  for  the  down  motion 
is  showno  The  pipe  seen  at  the  side  of  the  cylinder  is  called  a 
circulating  pipe,  and  its  office  is  to  permit  the  water  in  the  upper 
end  of  the  cylinder  to  pass  to  the  lower  end,  or  circulate,  while 
the  elevator  is  running  down.  As  can  be  clearly  seen  the  easiest 


Fig.  415.    Talve  of  Whittier  Machine.    Side  Elevation. 

way  in  which  to  make  a  vertical  cylinder  elevator  would  be  to 
have  the  lower  end  permanently  open,  and  to  let  water  into  the 
upper  end  to  force  the  piston  down  and  the  elevator  car  up,  and 
to  let  this  water  out  of  the  cylinder  to  permit  the  piston  to  run  up 
and  the  car  to  run  down.  A  little  reflection,  however,  will  show 
that  with  this  arrangement,  simple  as  it  is,  the  force  acting  to 
force  the  piston  down  when  the  latter  is  at  the  top  of  the  cylinder 
would  be  the  pressure  of  the  water  only,  while  when  the  piston  is 
At  the  bottom  of  the  cylinder  the  force  would  be  the  pressure  plus 


HANDBOOK    ON    ENGINEERING. 


967 


the  weight  of  water  above  the  cylinder.  Now  if  the  cylinder  is, 
say,  thirty  feet  long  this  water  would  increase  the  pressure  near- 
ly 14  pounds,  hence,  when  the  car  is  at  the  top  of  the  well  there 
would  be  a  greater  force  than  when  at  the  bottom,  and  the  load 
in  all  probability  would  be  less.  If  the  circulating  pipe  is  used, 
the  force  acting  on  the  piston  is  the  same  at  every  point  in  the 
stroke,  because  the  water  under  the  piston  is  drawn  up  by  the 
vacuum  that  tends  to  form  ;  therefore,  the  force  of  the  vacuum  act- 
ing  to  draw  down  the  piston  is  just  as  great  as  the  force  due  to 
the  weight  of  the  water  pressing  on  top  of  the  piston,  and  as  one 


Fig.  416.  Fig.  417. 

Automatic  Stop  Valve  for  Whittier  Machine. 

increases  as  fast  as  the  other  decreases,  the  two  balance  each 
other  at  all  times  and  the  force  acting  on  the  piston  remains  un- 
changed. 

The  valve  shown  in  Fig.  417  is  of  the  kind  used  with  a  hand 
rope  passing  through  the  car  to  operate  it.  The  hand  rope  is 
wound  around  the  sheave  13,  and  when  it  is  pulled  it  turns  the 
sheave,  the  direction  of  rotation  of  the  latter  depending  on  the  di- 
rection in  which  the  rope  is  moved.  The  connection  of  the  rope 
with  the  hand  sheave  is  made  such  that  if  the  car  is  going  up  the 
rope  must  be  pulled  up  to  stop,  and  if  coming  down  the  rope 


968 


HANDBOOK    ON     ENGINEERING. 


SECTION  OF  ELEVATOR    CYLINDER 
VALVE  SHOWING  WORK  ING 'PARTS] 

c 


Fig.  418.    Otis  Vertical  Elevator.   . 


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969 


must  be  pulled  down  to  stop.  The  rotation  of  the  sheave  turns 
the  pinion,  seen  in  Fig.  418,  and  thus  through  the  rack  on  the 
valve  stem  the  valve  is  shifted. 


r 


Fig.  419.    Otis  Vertical  Elevator  System. 

With  the  valve  in  the  position  A  of  Fig.  418  the  piston  cannot 
move  because  the  water  below  it  cannot  escape.  If  the  valve  is 
raised  to  the  position  of  JB,  the  water  under  the  piston  can  escape 


970 


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to  the  discharge  tank,  and  then  the  piston  can  move  down,  that 
is,  if  it  is  in  any  position  above  the  lowest.  If  the  valve  is 
lowered  to  the  position  C  then  the  water  in  the  upper  end  of  the 
cylinder  can  pass  through  the  valve  chamber  to  the  lower  end, 
and  the  pressure  being  equalized,  the  piston  will  move  upward, 
Fig.  419  is  an  illustration  that  serves  to  show  how  a  complete 


Fig.  420.    Otis  Valye. 

vertical  elevator  system  is  arranged,  although  in  practice  few 
installations  are  arranged  in  this  way  ;  generally  the  distance  be- 
tween the  tanks,  and  between  these  and  the  pump  and  elevator 
cylinder,  is  greater  than  here  shown.  In  this  illustration,  the 
pressure  tank  is  shown  directly  above  the  discharge  tank,  and 
the  steam  pump  that  supplies  the  water  is  located  at  the  side  of 


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the  discharge  tank.  The  pump  draws  the  water  from  the  dis- 
charge tank  and  delivers  it  into  the  pressure  tank.  The  elevator 
cylinder  draws  its  supply  from  the  pressure  tank  and  discharges 
it  into  the  lower  tank. 

VALVE  CONSTRUCTION. 

The  construction  of  the  valve  in  Fig.  418  can  be  understood 
more  fully  from  Fig.  42 00  It  will  be  seen  that  the  valve  pistons 
are  provided  with  cup  packings,  the  cup  in  E  being  set  so  as  to 
hold  pressure  acting  from  below,  and  F  having  packings  to  hold 
pressure  from  above.  The  valve  casing  opposite  F  has  a  brass 
lining  which  is  perforated  with  numerous  holes  about  one-quarter 
of  an  inch  diameter.  This  construction  is  used  in  all  hydraulic 
elevator  valves,  with  the  exception  of  very  small  pilot  valves 
which  are  in  some  cases  made  solid  and  ground  to  a  perfect  fit. 
This  is  done  so  as  to  reduce  the  friction  and  make  them  move 
more  freely.  The  perforated  brass  lining  for  the  valve  chamber 
is  used  so  as  to  prevent  the  cup  packing  from  dropping  into  the 
port  holes  as  it  passes  them.  The  main  pistons  of  hydraulic 
lifting  cylinders  are  made  so  as  to  be  packed  with  leather  cups, 
also  with  hemp  packing,  and  in  some  cases  have  a  combination  of 
cup  and  hemp  packing  ;  but  the  latter  alone  is  as  good  as  any- 
thing, provided  it  is  not  pressed  up  too  tight  by  the  follower. 
Cases  have  been  known  where  the  cylinder  has  been  burst  by 
having  the  packing  pressed  up  too  tight. 

The  vertical  elevator  shown  in  Fig.  418  is  provided  with  a  valve 
that  is  actuated  by  the  direct  pull  of  a  hand  rope.  This  con- 
struction which  was  used  exclusively  in  former  days,  is  now  em- 
ployed only  for  freight  elevators,  or  passenger  machines  that  run 
at  a  low  speed.  For  first  class  service,  such  as  the  elevators  of 
modern  office  buildings,  a  pilot  valve  is  provided  so  that  the  op- 
erator may  be  able  to  control  the  movement  of  the  car  with  cer- 


972 


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Fig.  421.    Otis  Tertical  Elevator  with  Pilot;  VaJv«  r«nt™i_ 


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973 


tainty  even  at  the  highest  speed.  An  Otis  vertical  elevator  for 
first  class  service,  provided  with  a  pilot  valve  is  shown  in  Fig.  421 
This  machine  is  geared  four  to  one.  The  main  valve  is  similar  to 


Fig.  422.    Otis  Vertical  Elevator,  showing  method  of  operating 
Pilot  Valre. 

that  of  Fig.  418,  the  only  difference  being  that  it  has  added  to  its 
upper  end  a  larger  piston,  the  office  of  which  is  to  move  the  valve. 
In  the  simple  arrangement  of  Fig.  418  the  car  is  stopped  automat- 


974 


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ically  at  the  top  and  bottom  landings  by  simply  placing  stop  balls 
on  the  hand  rope  is  such  position  that  they  will  be  struck  by  the 
car  at  the  proper  time.  This  construction  cannot  be  used  with 
the  pilot  valve  system  because  the  operating  ropes  are  held  by  the 
lever  in  the  car,  and  are  not  free  to  move.  Owing  to  this  fact,  a 
separate  automatic  stop  valve  is  added  and  is  connected  between 
the  main  valve  and  the  cylinder,  as  clearly  shown  in  Fig.  421. 


Fig.  423.    Otis  Vertical  Elevator.    Main  Valve  Used  with 
Pilot  Valve  Control. 

This  stop  valve  is  operated  by  means  of  a  cable  that  passes 
around  a  sheave  on  the  valve  spindle,  and  another  sheave  near 
the  top  of  the  building.  On  this  cable  there  are  stop  balls  and 
these  are  struck  by  an  arm  projecting  from  the  traveling  sheave 
frame,  the  action  being  the  same  as  in  the  horizontal  machines. 
The  way  in  which  the  valve  is  actuated  by  the  movement  of  the 
oar  lever  is  clearly  shown  in  Fig.  421,  but  the  operation  of  the 


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975 


valves  can  be  made  clearer  by  the  aid  of  Fig.  422.  When  through 
the  movement  of  the  car  lever  L,  the  sheaves  P  and  P*  are  ro- 
tated, the  pilot  valve  at  h  is  either  raised  or  depressed.  If  it  is 
depressed,  the  pressure  pipe  is  connected  with  the  space  T  above 
the  large  valve  piston,  through  the  pipes  g  and/.  The  pressure 
in  T  forces  the  valve  down  so  that  the  water  in  the  upper  end  of 


Fig.  424.    Details  of  Otis  Pilot  Valve. 

the  lifting  cylinder  can  circulate  through  pipe  G  to  the  lower  end 
of  the  cylinder  and  permit  the  piston  to  go  up  and  the  car  to  de- 
scend. If  the  pilot  valve  is  raised,  the  space  T  is  connected  with 
the  discharge  through  pipe/ and/  and  the  water  escapes,  and  as 
the  pressure  above  the  large  valve  piston  is  removed,  the  valve 
rises  and  thus  the  lower  end  of  the  cylinder  is  connected  with  the 


97()  HANDBOOK    ON   ENGINEERING. 

discharge,  and  the  water  runs  out,  while  the  pressure  water 
passes  through  port  Vio  the  circulating  pipe  G  and  thus  to  the 
upper  end  of  the  cylinder. 

The  construction  of  the  main  valve  can  be  clearly  understood 
from  the  drawing  Fig.  423  which  is  a  vertical  section.  As  will  be 
seen  the  only  difference  between  it  and  the  valve  Fig.  420  is  that 
it  is  provided  with  the  additional  motor  piston  G  which  is  in  the 
position  occupied  by  the  rack  and  pinion  in  the  latter  drawing, 
The  pilot  valve  can  be  understood  from  Fig.  424  in  which  the  pipe 
outlets  are  marked  to  correspond  with  Fig.  422. 

Additional  light  can  be  thrown  upon  the  operation  of  the  pilot 
and  main  valves  by  the  aid  of  Fig.  425  which  is  a  vertical  eleva- 
tion of  the  valve  gear  the  same  as  that  shown  in  Fig.  422,  but  on 
a  larger  scale,  and  divested  of  the  complication  due  to  the  pipe 
connections.  The  sheave  31  is  rotated  by  the  movement  of  the 
car  lever,  and  the  crank  upon  shaft  32  moves  the  lever  17  through 
the  connecting  rod  18.  As  the  pilot  valve  moves  easier  than  the 
main  valve,  this  movement  of  17  shifts  the  pilot  valve,  through 
rod  19.  If  the  pilot  valve  is  depressed,  pressure  water  entering 
through  ports  24  passes  out  through  ports  26  and  enters  the  space 
at  top  of  main  valve  chamber,  above  motor  piston  8.  The  pres- 
sure forces  the  main  valve  down  and  the  upper  end  11  of  valve  13 
uncovers  the  ports  at  12  so  that  the  water  in  the  upper  end  of  the 
cylinder  can  pass  through  the  valve  to  the  lower  end  and  the  pis- 
ton can  go  up,  and  the  car  come  down.  If  the  pilot  valve  is 
raised,  ports  26  are  connected  with  the  lower  end  of  pilot  valve 
chamber,  and  the  water  above  piston  8  can  escape,  so  that  the 
main  valve  may  move  up  and  connect  ports  12  with  the  discharge 
pipe.  It  will  be  noticed  that  for  either  movement  of  the  pilot 
valve,  the  following  movement  of  the  main  valve  acts  through 
lever  17  to  return  the  pilot  to  the  stop  position,  and  the  further 
the  latter  is  moved  by  the  rotation  of  31,  the  further  the  main 
valve  will  have  to  travel  to  return  the  pilot  to  the  stop  position ; 


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977 


Fig,  425.     Otis  Differential 
and  Pilot  Valve* 


978 


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thus  the  extent  to  which  the  main  valve  is  moved  is  in  direct  pro 
portion  to  the  extent  to  which  31  is  rotated,  and  this  is  in  pro 
portion  to  the  extent  to  which  the  car  lever  is  moved. 


Fig.  426.    Otis  Main  Valve  with  Magnetically  Operated  Pilot  Yalre. 

Sometimes  hydraulic  elevators  are  installed  in   private   houses, 
or  are  used  to  operate  dumb  waiters,  and  in  either  case  an  opera= 


HANDBOOK    ON    ENGINEERING. 


979 


tor  to  run  the  car  is  not  required.  As  a  rule  elevators  of  this 
kind  are  operated  by  electric  machines,  but  when  hydraulic  ma- 
chines are  so  used,  they  are  arranged  in  the  same  way,  that  is, 
so  that  they  may  be  operated  by  means  of  push  buttons  at  the 
several  floors  and  in  the  car.  To  make  the  hydraulic  valve  gear 
so  as  to  be  electrically  operated,  all  that  is  necessary  is  to  pro- 
vide magnets  that  will  move  lever  17  in  the  same  way  as  it  is 
moved  by  the  rotation  of  sheave  31.  A  valve  gear  provided  with 


SUPPLY 


Fig.  427.     Pipe  Connections  for  Fig.  426. 

such  magnets  is  shown  in  Fig.  426,  in  which  M  M'  are  electro- 
magnets, and  A  A'  iron  armatures  attached  to  the  lever  B.  If 
current  is  turned  onto  the  magnet  M ,  armature  A  is  drawn  down 
and  through  rod  0  lever  D  is  pushed  up  carrying  the  pilot  valve 
with  it.  If  current  is  turned  onto  magnet  JfcP,  armature  A'  is 
drawn  down  and  then  G  pulls  D  down  and  with  it  the  pilot  valve. 
The  action  of  the  main  and  pilot  valves  is  the  same  as  in  Fig.  425, 


980 


HANDBOOK    ON    ENGINEERING. 


The  pilot  valve  for  this  magnet  control  is  made  so  as  to  fit  tight 
by  grinding,  so  as  to  get  rid  of  the  friction  of  the  cup  packings. 
The  way  in  which  the  pilot  valve  is  connected  with  the  main 
valve  chamber,  and  the  supply  and  discharge  pipes  is  shown  in 
Fig.  427.  Two  strainers  are  placed  in  the  supply  connection,  so 
that  by  means  of  the  three-way  cocks  shown  either  one  may  be 


Fig.  428.    Photographic  Yiew  of  Fig.  427. 

disconnected  whenever  it   is  desired  to  clean   it.     Fig.  428  is  a 
photographic  view  of  this  type  of  magnetic  valve  gear. 

With  this  arrangement  of  magnets,  the  current  for  operating 
them  is  drawn  from  an  incandescent  lighting  circuit.  It  is 
necessary  sometimes,  however,  to  arrange  the  apparatus  so  that 
it  may  be  operated  by  current  obtained  from  primary  batteries, 


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981 


a  lighting  circuit  not  being  available.  As  the  current  from 
primary  batteries  is  weak,  and  expensive,  it  becomes  necessary  to 
modify  the  magnetic  devices  so  that  they  may  be  actuated  with 


Fig.  429.    Otis  Main  Valve  with  Magnet  Control  Adapted  to  Operate 
with  Battery  Current. 

smaller   currents.     This   is   accomplished   by    the   arrangement 
shown  in  Fig.  429.  In  this  construction,  the  magnets  M  M'  move 


982 


HANDBOOK    ON   ENGINEERING. 


a  pilot  valve  B  that  is  much  smaller  than  that  used  in  Fig.  426, 
and  works  correspondingly  easier.  This  secondary  pilot  controls 
the  flow  of  water  into  a  motor  cylinder  7),  and  the  piston  in  this 


3  WAY 


&URPLV  PIPE 


Fig.  480.    Pipe  Connections  for  Fig.  429. 

cylinder  acting  through  rod  E  moves  the  lever  P  in  the  same  way 
as  it  is  moved  by  the  magnets  in  Fig.  426.  As  valve  B  is  much 
smaller  than  the  main  pilot  valve  R  the  power  required  to  move 


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983 


it  is  much  less  than  that  required  for  the  construction  of  Fig.  426. 
From  Fig.  430,  which  shows  the  pipe  connections  of  this  double 
pilot  valve  construction,  the  operation  of  the  valves  can  be  more 
fully  understood.  The  actual  appearance  of  the  valve  gear  is 
shown  in  the  photographic  view  Fig.  431. 

A  complete  diagram  of  a  hydraulic  elevator  arranged  for  push 


Fig.  431.    Photographic  Yiew  of  Fig.  430. 

button  operation  is  shown  in  Fig.  432.  At  C  is  located  a  de- 
vice calld  a  floor  controller,  and  its  office  is  to  change  the 
circuit  connections  so  that  by  pressing  the  same  button  at  any 
floor,  the  car  may  be  caused  to  run  up,  if  it  is  below  that 
floor,  or  to  run  down  if  it  is  above  the  floor.  A  photo- 
graphic view  of  the  floor  controller  is  shown  in  Fig.  433. 


984 


HANDBOOK    ON    ENGINEERING. 


J. 


Fig.  432.    Otis  Private  House  Elevator,    Push  Button  Control. 


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985 


This  floor  controller  is  driven  by  chain  E  which  is  moved 
by  the  arm  F,  of  the  traveling  sheave.  The  chain  rotates 
a  shaft  that  carries  a  worm  that  meshed  into  gear  D  and 
thus  rotates  C.  The  controller  C  has  mounted  on  its  surface 
two  metallic  strips  that  are  connected  with  the  opposite  sides 
of  the  circuit.  Contact  brushes  rest  on  these  strips,  there  being 
one  for  each  floor.  The  contact  strips  are  set  spirally  on  the 
face  of  the  drum  of  0,  and  the  drum  travels  on  a  thread  that  is 
the  same  pitch  as  this  spiral  so  that  the  brushes  may  always  rest 
on  the  strips.  When  the  elevator  car  is  below  a  given  floor,  the 


Fig.  483.    Floor  Controller  for  Otis  Fash  Button  System.   Fig.  433a. 

brush  corresponding  to  that  floor  rests  on  one  of  the  metallic 
strips  forming  the  spiral,  but  when  the  car  is  above  this  floor  the 
brush  rests  upon  the  other  strip.  In  this  way  the  circuit  con- 
nections are  changed,  so  that  if  the  car  is  above  the  floor,  press- 
ing the  button  causes  the  car  to  run  down,  and  if  it  is  below  the 
floor,  pressing  the  same  button  causes  it  to  run  up.  The  way  in 
which  all  this  is  accomplished  is  made  clear  by  the  wiring  dia- 
gram, Fig.  434. 

Two  operating  batteries  are  shown,  and  either  one  can  be  used 


986  HANDBOOK    ON    ENGINEERING. 

by  turning  the  switch  in  the  proper  direction.  If  the  switch  is 
turned  to  close  the  circuit  the  current  will  flow  into  the  +  wire  all 
the  way  to  the  car  and  back  to  wire  A,  and  through  coils  a  b  to  c 
and  to  wire  B  which  connects  with  all  the  floor  and  car  push  but- 
tons. The  coils  a  b  and  contacts  c  represent  a  magnetic  switch 
with  the  two  coils  wound  in  opposition  to  each  other,  so  that  if 
current  passes  through  both,  contacts  c  remain  closed.  If  any 
one  of  the  push  buttons  is  depressed  the  current  will  pass  through 
it  to  the  corresponding  wire  of  the  set  1,  2,  3,  etc.,  and  through 
the  corresponding  coil  11,  22,  33,  etc.,  to  a  corresponding  floor 
controller  brush,  and  then  through  wire  n  and  the  upper  magnets 
back;to  the  battery.  The  coils  11,  22,  33,  etc.,  represent  mag- 
netic switches  that  close  the  contacts  seen  to  the  right  of  them 
when  a  current  passes.  As  soon  as  the  contacts  are  closed,  cur- 
rent flows  through  wire  m  from  the  junction  of  coils  a  b  and  then 
the  coil  b  being  cut  out,  the  circuit  with  B  is  broken  at  c,  so  that 
after  this  instant,  no  one  can  interfere  with  the  movement  of  the 
car  by  pressing  another  button  because  there  is  no  current  in  B. 
Thus  it  will  be  seen  that  as  soon  as  the  car  is  started  from  any 
floor,  or  from  the  car  itself,  all  the  push  buttons  are  cut  out  until 
the  trip  is  completed.  The  circles  seen  in  the  upper  part  of  the  + 
wire  represent  door  switches  at  the  landings,  that  are  open  when 
the  door  is  opened,  so  that  unless  the  landing  door  is  closed  the 
car  cannot  move.  As  soon  as  the  car  begins  to  move,  the  floor 
controller  begins  to  rotate,  and  when  the  car  reaches  the  floor 
corresponding  to  the  button  pushed,  the  controller  brush  through 
which  the  current  is  passing  passes  onto  the  break  between  the 
segments  n'  and  p'  and  the  circuit  through  the  magnets  is  broken 
and  the  ear  stops.  If  the  controller  brush  connected  with  the 
wire  through  which  the  current  comes  is  resting  onp',  insteadof  n' 
the  current  will  flow  through  the  lower  valve  magnets,  and  the  di 
rection  of  the  car  will  be  reversed.  In  Fig.  434  the  floor  control- 
ler is  shown  with  the  segments  eovering  less  than  half  a  circle,  so 


HANDBOOK    ON    ENGINEERING. 


987 


as  to  simplify  the  diagram,  but  in  the  actual  controller  they  are 
arranged  in  a  spiral  line  as  shown  in  Fig.  433,  so  as  to  give  more 
space  between  the  brushes. 


Fig.  434.    Wiring  Diagram  for  Otis  Push  Button  System. 
DOUBLE  POWER  HYDRAULIC  ELEVATORS. 

Hydraulic  elevators  of  the  types  so  far  explained  have  one  de- 
fect, and  that  is  that  it  requires  just  as   much  power  to  run  the 

14 


988  HANDBOOK    ON    ENGINEERING. 

car  up  empty  as  if  fully  loaded.  This  is  so  from  the  fact  that  in 
either  case  a  cylinder  full  of  water  must  be  used.  To  obviate 
this  loss  of  power,  the  Otis  Company  make  what  is  called  the 
double  power  system.  The  difference  between  this  and  the  ma- 
chines so  far  described  is  that  water  at  two  different  pressures  is 
used,  the  low  pressure  being  about  half  as  much  as  the  high  ;  gen- 
erally the  low  pressure  is  100  and  the  high  180  to  200  pounds. 
The  valves  are  so  arranged  that  for  small  loads  only  low  pressure 
water  is  used  the  high  pressure  being  reserved  for  heavy  loads. 

The  valves  of  the  double  pressure  system  are  shown  in  Fig.  435, 
and  as  will  be  seen  are  substantially  the  same  as  those  already 
shown,  the  actual  difference  being  that  the  piston  F  is  added  so 
as  to  control  the  flow  of  high  pressure  water.  The  pilot  valve  is 
made  so  that  its  first  movement  causes  motor  piston  E  to 
move  far  enough  to  let  on  the  low  pressure  water  only.  If  this 
is  not  sufficient  to  move  the  car,  the  operator  moves  the  lever 
further,  and  then  the  pilot  valve  moves  far  enough  to  lift  valve  F 
above  the  lower  edge  of  port  i  so  that  high  pressure  water  may 
flow  into  the  cylinder.  In  practice  it  is  found  that  there  is  an  in- 
jector effect  produced  which  draws  low  pressure  water  in  together 
with  the  high  pressure,  so  that  if  the  load  in  the  car  is  more  than 
the  low  pressure  can  lift,  but  less  than  the  maximum  capacity  of 
the  high  pressure,  then  water  is  drawn  from  both  sources,  and 
the  amount  drawn  from  each  one  is  nearly  in  proportion  to  the 
load. 

HIGH  PRESSURE   HYDRAULIC  ELEVATORS. 

As  low  pressure  elevators  take  up  a  considerable  room,  on  ac- 
count of  the  large  size  of  the  lifting  cylinders,  the  connecting 
pipes  and  the  tanks,  high  pressure  machines  are  frequently  in- 
stalled in  large  office  buildings,  specially  if  these  occupy  small 
floor  space.  High  pressure  machines  are  made  horizontal  as 
well  as  vertical,  but  more  are  made  of  the  latter  type.  A  high 


HANDBOOK   ON   ENGINEERING. 


989 


Fi?.  435.    Otis  Double  Pressure  Eleyator, 


990  HANDBOOK    ON   ENGINEERING. 


HANDBOOK    ON   ENGINEERING. 


991 


S3 

•c 

I 


$ 


992  HANDBOOK    ON    ENGINEERING. 


as  the  pilot  valve  is  operated  with  low  pressure  water.  The  con- 
struction of  the  valves  is  shown  in  Fig.  438,  in  which  the  pilot  is 
on  the  left,  and  is  moved  by  the  connecting  rod  E,  which  in 
turn  is  moved  by  L  through  rod  D.  The  motor  cylinder  is  in 
the  center,  and  the  main  valve  on  the  right.  The  pilot  valve  con- 
trols the  flow  of  water  into  the  motor  cylinder,  and  when  the 
piston  Amoves,  the  piston  rod  Cr,  through  the  connecting  arms 
J  and  P,  moves  the  main  valve ;  and  also  through  lever  JT,  which 
swings  around  the  upper  end  of  D,  moves  the  pilot  valve  back  to 
the  stop  position.  The  pilot  valve  is  operated  with  low  pressure 
water  because  it  would  not  be  practical  to  use  high  pressure 
on  account  of  the  smallness  of  the  ports.  In  fact  the  first  ma- 
chines of  this  type  were  made  with  high  pressure  to  operate  the 
pilot  valves,  but  they  gave  a  great  deal  of  trouble  on  account  of 
the  wearing  out  of  the  ports  and  valves.  The  sheave  that  moves 
the  pilot  valve  is  attached  to  the  disc  S,  or  to  the  shaft  on  which 
this  disc  is  mounted. 

In  Fig,  437  the  automatic  stop  valve  is  located  near  the  main 
valve,  at  the  lower  end  of  the  guides  for  the  traveling  sheave,  and 
is  actuated  by  levers  that  extend  in  the  path  of  the  sheave  frame, 
so  as  to  be  struck  by  it  at  the  proper  time.  The  valve  is  also 
placed  just  below  the  lower  end  of  the  lifting  cylinder,  and  is 
actuated  by  a  chain  that  passes  round  a  sheave  mounted  on  its 
spindle  and  runs  by  the  side  of  the  traveling  sheave  frame  to 
the  lower  end  where  it  passes  around  a  carried  sheave.  In  this 
construction  the  chain  has  stop  balls  placed  on  it  at  both  ends, 
and  these  are  struck  by  a  projecting  arm  on  the  sheave  frame  at 
the  proper  time  to  stop  the  car  at  the  upper  and  lower  floors. 
The  valve  used  with  this  arrangement  is  shown  in  Figs.  439-440, 
441  and  442.  The  sprocket  wheel  around  which  the  chain  passes 
is  at  A,  and  when  the  arm  on  the  traveling  sheave  frame  strikes 
one  of  the  stop  balls,  A  is  rotated  and  with  it  the  valve  #,  Fig. 
4:4:2.  The  shaft  of  A  carries  a  pinion  that  meshes  into  a  gear  on 


HANDBOOK    ON    ENGINEERING . 


993 


Fig*  437t    HigU  Pressure  Hydraulic  Elevator  System  witli  Inverted 

Plunger, 


994  HANDBOOK    ON    ENGINEERING. 

the  valve  shaft,  Fig.  440,  so  that  A  turns  through  several  revo- 
lutions to  close  the  valve  G.  The  wheel  C  is  provided  to  return 
the  v-'tlve  to  the  central  position.  A  strap,  to  which  a  weight  is 
attached,  is  secured  to  G  and  passes  between  the  small  wheels 
D  7),  Fig.  440.  The  weight  is  heavy  enough  to  rotate  C. 

The  movement  of  A  is  geared  down  so  as  to  produce  a  slow 
closing  of  the  stop  valve  and  thus  prevent  violent  stopping  of  the 
elevator.  The  valve  G  is  made  so  as  not  to  fit  perfectly,  and  is 
held  against  the  seat  in  stopping  by  the  pressure  of  the  water, 
but  when  the  pilot  valve  is  turned  to  run  the  car  in  the  opposite 
direction,  the  current  of  water  through  G  changes  its  direction 
and  the  valve  is  lifted  from  its  seat  so  that  water  can  leak  through 
fast  enough  to  give  the  car  a  smooth  start.  As  soon  as  the  car 
moves,  the  arm  that  struck  the  stop  balls  moves  out  of  the  way, 
and  then  the  weight  suspended  from  G  rotates  the  latter  and 
returns  the  valve  to  the  central  position. 

Fig.  443  shows  two  views  of  a  valve  not  shown  in  Fig.  437. 
This  valve  is  simply  a  speed  governor.  In  high  office  buildings 
elevators  run  at  very  high  speed,  500  to  600  feet  per  minute,  and 
with  such  velocities  it  is  possible  for  a  car  to  run  away  if  the 
load  is  light  and  the  operator  opens  the  valve  too  wide.  The 
object  of  Fig.  443  is  to  prevent  such  run  aways  by  checking 
the  flow  of  water.  In  the  sectional  view  of  this  valve  it  will  be 
seen  that  the  pipes  are  connected  with  the  outlets  C  and  D. 
Now  the  water  to  pass  from  one  to  the  other  has  to  flow 
through  the  valve  piston  B.  This  piston  has  small  holes  E 
for  the  water  to  flow  through,  and  some  pressure  is  lost  by  the 
passage  of  the  water  through  these  holes,  the  amount  of  pres- 
sure increasing  as  the  velocity  of  the  water  increases.  The 
spring  JTact8  to  hold  piston  B  in  the  central  position,  and  is  ad- 
justed so  as  to  hold  against  the  pressure  developed  by  the  high- 
est velocity  at  which  it  is  desired  that  the  water  should  flow.  If 
+,m's  velocity  is  exceeded,  the  pressure  due  to  the  loss  of  head  in 


HANDBOOK    ON    ENGINEERING. 


995 


Fig.  438.    YalYesUsedinFir.437. 


996 


HANDBOOK    ON    ENGINEERING. 


passing  through  holes  E  will  increase,  and  then  B  will  be  carried 
to  one  side  of  the  center  and  some  of  the  holes  in  sleeve  F  will 
be  covered,  thus  reducing  the  opening  through  which  the  water 
can  pass,  and  thereby  checking  the  speed  of  the  elevator. 

Figs.  444  and  445  are  two  views  of  the  accumulator.  An  ac- 
cumulator is  simply  a  hydraulic  cylinder  standing  upright  and 
provided  with  a  plunger  that  is  loaded  with  iron  weights  until 
the  desired  pressure  of  water  is  obtained.  In  the  illustrations,  K 


Fig.  439.  Fig.  440. 

Automatic  Stop  Valve  Used  in  Fig.  437. 

is  the  cylinder  and  L  the  plunger,  which  is  provided  with  a  cross- 
head  at  the  top,  from  which  depend  rods  M  M  that  hold  the 
weights  A.  These  weights  are  made  with  a  hole  in  the  center 
large  enough  to  clear  the  cylinder,  so  that  when  the  water  is 
all  out,  the  weights  envelop  the  cylinder.  This  construction  is 
used  in  cases  where  it  is  desired  to  economize  head  room ;  in 
other  cases  the  weights  are  set  directly  on  top  of  the  plunger. 
To  prevent  pumping  enough  water  into  the  accumulator  to  force 
the  plunger  out  the  top.  and  also  to  prevent  drawing  out  so 


HANDBOOK    ON    ENGINEERING. 


997 


much  as  to  empty  the  cylinder  and  allow  the  plunger  to  strike  the 
bottom,  automatic  stops  are  provided  to  control  the  pump,  and 
also  the  flow  of  water  from  the  accumulator.  The  rope  to  which 
the  weight  B  is  attached  runs  to  the  valve  of  the  pump,  and 
when  the  accumulator  is  full  this  weight  B  is  lifted  by  shelf  Q 
and  then  the  pump  valve  is  closed.  The  flow  of  water  in  or  out 
of  the  accumulator  is  controlled  by  valve  D.  This  valve  is  moved 
by  an  arm  on  the  weights  A  striking  the  stop  balls  2^  on  the 
chain  E.  When  the  water  is  at  the  low  limit,  the  lower  F  is 
struck  and  this  closes  valve  D  so  that  while  water  can  flow  in 
none  can  pass  out.  If  the  accumulator  is  full,  the  upper  F  is 


Fig.  441.  Fig.  442. 

Automatic  Stop  Valve  Used  in  Fig.  437. 

struck  and  then  D  is  reversed,    so  that  no    more    water    can    be 
pumped  in,  but  water  can  flow  out  freely. 

Valve  D  is  shown  in  Figs.  446  and  447.  In  the  first  drawing, 
the  arrows  A  indicate  the  course  of  the  water  flowing  into  the  ac- 
cumulator, and  the  outgoing  path  is  indicated  by  the  dotted  ar- 
rows. The  check  valve  in  the  outlet  passage  E  opens  upward, 
and  check  valve  in  the  inlet  passage  F  opens  downward.  If 
valve  D  is  in  the  central  position,  water  can  pass  through  it  in 
either  direction,  but  if  rotated  in  one  direction  it  will  stop  the  flow 
through  E  and  if  rotated  in  the  opposite  direction  it  will  stop  the 
flow  through  F.  The  passages  E  and  F  surround  valve  D,  as 


998 


HANDBOOK    ON    ENGINEERING. 


seen  in  Fig.  447  but  the  ports  in  the  valve  D  as  well  as  the  valve 
chamber,  are  so  shaped  that  E  &ndF  can  be  connected  separately 
with  B  but  not  directly  with  each  other. 


Fig.  443.    Speed  Controller  Used  in  Fig.  437. 

PLUNGER  ELEVATORS. 

In  plunger   elevators,  the  lifting  cylinder   is  placed   in  a  hole 
bored  down  in  the  ground  directly  under  the  centre  of  the  car. 


HANDBOOK    ON    ENGINEERING 


999 


The  plunger  pushes  the  car  to  the  top  of  the  building;  therefore, 
the  plunger  and  cylinder  both  have  to  be  made  a  few  feet  longer 
than  the  height  to  which  the  elevator  is  raised.  The  cylinder  is 


Fig.  444.  Fiff.  445. 

Accumulator  Used  in  Fig.  437. 


made  of  steel  pipe,  as  many  lengths  as  may  be  necessary  bei&g 
joined  together  by  means  of  sleeve  couplings.  The  ends  of  the 
pipe  sections  are  turned  square  with  the  axis  of  the  pipe,  and  the 


1000 


HANDBOOK    ON    ENGINEERING. 


threads  are  cut  true  so  that  when  the  several  lengths  are  joined 
they  may  form  a  straight  cylinder.  The  plunger  is  also  made  of 
lengths  of  steel  pipe  which  are  joined  by  internal  sleeves.  These 
sleeves  are  made  extra  long  so  as  to  give  the  plunger  just  as 
much  strength  at  the  joints  as  at  other  points.  The  pipes  form- 
ing the  plunger  are  turned  true  and  made  smooth  so  as  to 'slide 
through  the  stuffing  box  with  as  little  friction  as  possible,  and 
also  so  as  to  make  a  tight  joint  at  the  box.  The  top  of  the  cyl- 
inder consists  of  a  casting  provided  with  an  outlet  for  the  water 


Fig.  446. 


Fig.  447. 


Valve  for  Accumulator,  Figs.  444  &  445. 

pipe  to  attach  to, and  a  stuffing  box  at  the  top ;  the  latter  is  in 
some  cases  made  separate  and  bolted  to  the  main  casting. 

The  plunger  is  made  from  six  to  seven  inches  in  diameter,  and 
the  cylinder  is  about  two  inches  larger,  so  that  only  the  top  cast-" 
ing  has  to  be  finished  to  fit  the  plunger.  The  lower  end  of  the 
plunger  is  finished  off  with  a  casting,  The  hole  in  the  ground  is 
made  about  13  inches  in  diameter,  and  when  the  cylinder  is  in 
place,  the  space  between  it  and  the  sides  of  the  hole  is  filled  with 
sand. 


HANDBOOK   ON   ENGINEERING.  1001 

Plunger  elevators  have  been  made  for  years  for  short  runs,  but 
it  is  only  within  the  past  few  years  that  they  have  been  installed 
for  high  buildings  and  for  all  classes  of  service.  While  there  are 
probably  many  concerns  that  make  plunger  machines  for  side- 
walk elevators,  and  other  low  runs,  there  are  only  two  companies 
that  make  them  for  high  speed  passenger  service  in  high  office 
buildings.  These  concerns  are,  The  Plunger  Elevator  Company 
and  The  Standard  Plunger  Elevator  Company,  both  of  which 
have  their  works  in  Worcester,  Mass. 

The  general  arrangement  of  the  elevator  made  by  the  Standard 
Company  is  shown  in  the  half  tone  Fig.  448,  and  the  elevator  of 
the  Plunger  Company  is  shown  in  half  tone  Fig.  449.  From  both 
these  illustrations  it  will  be  seen  that  ropes  pass  from  the  top  of 
the  car  over  an  overhead  sheave  and  down  to  a  counterbalance 
weight.  If  the  building  is  high,  say  from  150  to  300  feet,  the 
plunger  will  weigh  so  much  that  a  part  of  it  will  have  to  be 
counterbalanced,  so  that  the  counterbalance  weight  will  be 
heavier  than  the  car  proper,  and  will  actually  lift  the  upper  end 
of  the  plunger.  Owing  to  this  fact,  the  plunger  has  to  be  firmly 
secured  to  the  bottom  of  the  car  so  that  there  may  be  no  dan- 
ger of  its  pulling  away. 

The  fact  that  the  counterbalance  weight  is  heavier  than  the 
car  serves  to  increase  the  stiffness  of  the  plunger  for  the  reason 
that  the  upper  end  is  subject  to  a  tension,  instead  of  compression, 
and  the  tendency  to  buckle  is  confined  to  the  lower  end.  On  this 
account  the  plungers  do  not  buckle  even  when  200  to  300  feet 
long,  notwithstanding  that  the  diameter  is  between  six  and  seven 
inches.  Sometimes  when  making  a  quick  stop  coming  down 
the  plunger  may  spring  slightly,  but  it  at  once  returns  to  the 
straight  position. 

In  the  Standard  Elevator  Fig.  448  the  main  valve  is  at  A,  the 
pilot  valve  being  at  the  extreme  right  side  end,  and  is  moved  by 
the  car  lever  through  the  rope  connection  as  clearly  shown.  The 


1002 


HANDBOOK    ON    ENGINEERING* 


I 


HANDBOOK    ON    ENGINEERING.  1003 

automatic  stop  valves  to  stop  the  car  at  the  top  and  bottom  land- 
ings are  located  below  the  main  valve  at  B,  the  lower  limit  valve 
being  at  L  and  the  top  valve  at  Lf.  These  limit  valves  are  act- 
uated by  the  ropes  E  and  F.  The  first  being  attached  to  the 
bottom  of  the  car  on  the  left  side.  This  rope  runs  over  a  small 
sheave  and  down  and  around  the  sheave  on  the  end  of  the  lever 
L,  thence  to  the  top  of  the  elevator  well,  over  a  sheave  and  down 
to  the  top  of  the  car  where  it  is  fastened  on  the  right  side.  The 
other  rope  starts  from  the  left  side  of  the  top  of  the  car,  and  run- 
ning over  a  sheave  at  the  top  of  the  well  runs  down  and  around 
the  sheave  on  the  end  of  L'9  and  thence  up  to  the  bottom  of  the 
car  on  the  right  side.  Each  one  of  these  ropes  is  given  a  sharp 
bend  when  the  elevator  reaches  its  end  of  the  well,  and  in  that 
way  the  lever  of  the  corresponding  limit  valve  is  raised,  and  the 
valve  is  closed  so  as  to  stop  the  car.  The  water  from  the  pressure 
tank  enters  through  pipe  S  to  the  main  valve  chamber,  and 
passing  down  through  the  limit  valve  chamber  reaches  the  cylin- 
der. In  escaping  from  the  cylinder  the  water  passes  through  the 
limit  valve  to  the  main  valve  and  thence  to  the  discharge  pipe  D. 
The  operation  of  the  valves  will  be  explained  further  on. 

In  Fig.  449  the  limit  valves  are  actuated  in  substantially  the 
same  manner  as  in  Fig.  448,  but  the  ropes  are  stationary,  their 
upper  ends  being  fastened  to  the  framing  at  the  top  of  the  eleva- 
tor well  and  the  lower  ends  to  the  valve  levers.  In  this  elevator, 
the  main  valve  is  connected  between  the  cylinder  and  the  limit 
valves,  which  is  just  the  opposite  of  the  arrangement  in  Fig.  448. 

The  details  of  construction  of  the  cylinder  and  plunger  of  the 
Standard  machine  are  shown  in  the  line  drawings,  Figs.  450  and 
451,  the  first  being  a  vertical  elevation  in  section,  and  the 
other  an  outside  view  taken  at  right  angles  to  Fig.  450.  In  the 
last  named  drawing,  the  long  sleeve  couplings  inside  of  the 
plunger  can  be  clearly  seen,  also  the  construction  of  the  top 

36 


1004 


HANDBOOK    ON    ENGINEERING. 


Fig.  449.    Is  Plunger  Elevator  of  the  Plnnerer  Elevator  C&. 


HANDBOOK    ON    ENGINEERING.  1005 

cylinder  casting,  with  the  water  pipe  opening  A.  Within  the 
plunger  there  is  a  strong  steel  cable  B  that  is  secured  to  the  floor 
framing  of  the  car,  and  runs  down  to  the  bottom  of  the  plunger 
where  it  is  firmly  secured.  This  is  an  extra  safeguard  to  hold 
the  plunger  if  from  any  cause  it  should  break  away  from  the  un- 
derside of  the  car  floor.  The  bottom  of  the  plunger  terminates 
in  a  brass  casting  (7,  which  is  made  of  brass  so  that  that  portion 
of  it  that  does  not  pass  through  the  stuffing  box  when  the  car 
reaches  the  top  floor,  may  not  become  rough  by  rusting.  This 
casting  carries  at  its  lower  end  three  copper  wire  brushes  d  which 
serve  to  prevent  the  lower  end  of  the  plunger  from  hitting  the 
sides  of  the  cylinder,  and  also  will  permit  water  to  run  out  of 
the  top  of  the  cylinder  if  for  any  reason  the  car  should  run  above 
the  top  limit.  This  is  a  safety  arrangement  provided  so  that  the 
car  cannot  run  into  the  overhead  beams. 

The  valves  of  the  Standard  Plunger  Elevator  are  shown  in  Fig. 
452.  The  supply  pipe  is  at  £,  and  the  discharge  pipe  at  E. 
When  the  car  runs  up  the  main  valve  is  moved  to  the  right  carry- 
ing E  fast  enough  to  permit  water  from  S  to  pass  S' '.  W7hen  run- 
ning up,  valve  Fisto  the  left  of  the  position  shown,  so  that  from 
S'  the  water  can  pass  to  D  and  to  the  cylinder.  In  coming 
down,  the  main  valve  is  moved  to  the  left  far  enough  for  T  to 
connect  E  with  E'  and  then  the  water  in  the  cylinder  can  pass 
out  through  D  to  E'  and  through  the  main  valve  chamber  to  E. 

The  pilot  valve  is  located  at  the  right  of  the  main  valve,  JV 
being  its  stem.  The  lever  K  is  moved  by  the  car  lever  through 
the  running  rope  gear  as  shown  in  Fig.  448.  If  K  is  raised,  the 
rod  L  lifts  the  shaft  that  carries  pinion  P,  and  thus  the  pilot 
valve  is  raised,  so  that  the  water  from  the  supply  pipe  /Scan  pass 
through  A  to  the  pilot  valve  chamber  and  come  out  through 
pipe  C  to  pipe  P  and  thence  to  space  M  back  of  the  motor  piston 
Q  of  the  main  valve.  This  water  will  move  the  main  valve  to 
the  right  and  cause  the  elevator  to  ascend.  At  the  same  time 


1006 


HANDBOOK    ON    ENGINEERING. 


DETAILS  OF  PLUNGER  ELEVATOR  PARTS  AND  CONNECTION 

Fig.  450.  For  Standard  Plunger  Elerator.  Fig.  45 


HANDBOOK   ON   ENGINEERING. 


1007 


the  movement  of  rack  U  will  rotate  pinion  P  and  cause  it  to  run 
down  on  the  thread  in  L  and  thus  lower  the  pilot  valve  to  the 
central  position.  In  going  down  the  lever  K  is  depressed  and 
the  movement  of  the  pilot  valve  is  in  the  opposite  direction  so 
that  pipe  P  is  connected  through  the  lower  end  of  the  pilot  valve 
chamber  with  the  pipe  leading  to  the  discharge,  and  in  this  way 
end  Q  of  motor  cylinder  is  emptied  and  the  main  valve  moves  to 
the  left.  From  the  foregoing  it  will  be  seen  that  the  action  of 


Fig.  452.    Pilot  Controlling  Valve  for  Standard  Plunger  Elevator 
and  Automatic  Stopping  Yalve  for  End  of  Bun. 

the  pilot  and  main  valves  in  this  construction  is  substantially  the 
same  as  in  other  types  of  elevators,  in  fact  all  hydraulic  elevator 
pilot  valve  gears  act  upon  the  same  principle,  and  only  differ  in 
construction.  The  action  of  the  limit  valve  is  not  clearly  seen 
from  Fig.  452,  because  in  this  drawing  the  end  levers  are  in  an  in- 
rerted  position,  this  being  done  so  as  to  contract-the  drawing  by 
shortening  the  connections  S'  E'.  If  it  is  kept  in  mind  that  the 
end  levers  are  reversed,  as  shown  in  Fig.  448,  then  it  can  be  seen 


1008  HANDBOOK   ON   ENG1NUE1UNG. 

that  when  W  is  raised,  Yis  closed,  and  that  the  same  is  true  of 
Z  and  F.  The  valves  G  G  at  the  inner  ends  of  ]Tand  Z  are  for 
the  purpose  of  stopping  the  ports  from  S'  and  E'  if  the  ropes  that 
operate  the  limit  valves  should  break  or  run  off  the  sheaves.  It 
will  be  noticed  that  at  the  lower  end  of  the  shaft  of  pinion  P 
there  are  two  spiral  cams,  and  a  stationary  cam  is  located  be- 
tween them.  These  cams  are  for  the  purpose  of  preventing  a 
too  sudden  stop  of  the  car,  by  an  instantaneous  closing  of  the 
main  valve.  If  the  main  valve  is  closed  instantly,  when  the  car 
is  running  up,  the  headway  will  keep  the  car  moving  up  some 
distance  and  as  water  cannot  flow  into  the  cylinder,  the  plunger 
will  leave  the  top  of  the  water.  The  headway  of  the  car  will 
then  soon  stop  and  its  weight  will  bring  it  back  and  cause  the 
plunger  to  strike  the  top  of  the  water  in  the  cylinder,  and  pro- 
duce an  uncomfortable  jolt.  If  the  sudden  stop  is  effected  when 
the  car  is  going  down  the  plunger  will  buckle  to  some  extent  to 
relieve  the  jar.  The  cams  below  P  prevent  these  sudden  stops 
because  L  cannot  move  P  vertically  any  faster  than  the  cams 
turn  around  so  that  even  if  K  is  moved '  to  the  stop  position  in- 
stantly, the  pilot  valve  will  not  move  any  faster  than  is  per- 
missible. 

The  main  and  pilot  valves  of  the  Elevator  made  by  the  Plunger 
Co.,  Fig.  449  are  shown  in  Fig.  453.  The  pilot  valve  is  moved  by 
lever  H.  There  are  two  valves  used  to  perform  the  pilot  work, 
L  the  pilot  valve  proper,  and  JT,  which  is  called  a  throttle.  If  H 
is  lifted,  the  lever  I  will  swing  arouud  its  upper  end  and  move  L 
to  the  left.  The  supply  pipe  is  at  E,  and  is  connected  with 
chamber  1  by  port  0,  and  1  is  connected  with  2,  so  that  when  1 
is  moved  to  the  left,  water  can  pass  from  1  to  2  thence  through 
3  to  4  and  through  pilot  valve  to  passage  6  and  to  the  back  end 
of  motor  piston-  cylinder,  and  force  the  main  valve  to  the  right, 
BO  that  water  from  E  may  pass  to  F  and  to  the  lifting  cylinder. 
The  movement  of  the  main  valve  to  the  right  will  cause  K  to 


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1009 


1010  HANDBOOK    ON    ENGINEERING. 

move  to  the  left,  and  L  to  the  right,  thus  bringing  the  pilot  valve 
back  to  the  stop  position,  just  as  in  all  other  pilot  valve  arrange- 
ments. The  movement  of  K  to  the  left  closes  the  opening  be- 
tween d  and  /  at  e  so  that  the  only  way  for  water  to  pass  from 
one  space  to  the  other  is  through  the  opening  opposite  the  end 
of  screw  N.  This  construction  is  for  the  same  purpose  as  the 
cams  on  the  shaft  of  pinion  P  in  Fig,  452,  that  is,  to  prevent  too 
sudden  a  stoppage  of  the  elevator.  The  operation  is  as  follows : 
Suppose  the  operator  moves  the  car  lever  rapidly  to  the  stop  posi- 
tion, then  lever  H  swings  down  rapidly,  and  carries  the  pilot  valve 
with  it,  but  the  water  in  the  back  of  the  motor  cylinder,  to 
reach  the  discharge  pipe  must  follow  the  path  indicated  by  6 
&,  c,  djf,  and  g  to  G.  Now  as  we  have  shown,  the  opening  be- 
tween d  and  /  through  K  has  been  closed ,  so  that  the  water  has 
to  pass  through  the  hole  opposite  screw  N  and  by  properly  ad. 
justing  the  position  of  this  screw  the  passage  can  be  made  as 
small  as  desired,  and  the  time  required  for  the  water  to  pass  can 
be  as  much  as  may  be  necessary  to  prevent  the  main  valve  from 
closing  too  rapidly. 

The  operation  of  this  valve  in  going  down  is  the  reverse  of  that 
above  explained.  On  the  down  trip  the  pilot  valve  water  is  dis- 
charged in  stopping  through  spaces  2,  4,  and  passes  through 
opening  opposite  screw  M ,  and  is  adjusted  by  this  screw. 

The  operation  of  the  limit  valves  in  Fig.  449  can  be  easily  under- 
stood  from  the  line  drawing  Fig.  454.  The  pipes  A  and  B  con- 
necting the  limit  valves  with  the  pilot  valve  chamber  are  for  the 
purpose  of  giving  a  direct  connection  between  the  supply  and 
discharge  and  the  pilot  valve.  The  main  valve  shown  in  Fig. 
454  is  not  a  duplicate  of  that  in  Fig.  453,  the  principal  difference 
between  them,  however,  is  that  in  the  latter  all  the  connections 
are  made  by  passages  cast  in  the  valve  casing,  while  in  the  former 
these  connections  are  made  by  outside  piping. 

Fig*  455  shows  in  outline  a  simplified  form  of  plunger  elevator 


HANDBOOK    ON   ENGINEERING. 


ion 


Fig.  454.    Fine  Illustration  of  the  Plunger  Elevator  Company's 
Elevator  for  Pilot  Valve  Control. 

made  by  the  Plunger  Co,  for  freight  service.     In  this  arrange- 
ment the  valve  is  actuated  by  a  hand  rope,  and,  therefore,  is  of 


]012  HANDBOOK    ON    ENGINEERING. 

simple  construction,  without  a  pilot  valve.  The  limit  valves 
are  also  dispensed  with  as  their  office  is  filled  by  the  stop  balls 
attached  to  the  hand  rope.  The  valve  used  in  Fig.  455  is  shown 
in  Fig.  456  and  is  so  simple  as  to  require  no  explanation.  It 
may  be  well  to  mention,  however,  that  it  shows  the  exhaust  pipe 
connection  on  the  side  of  the  valve  chamber,  instead  of  at  the 
end.  This  construction  is  for  the  purpose  of  effecting  a  more 
perfect  balancing  of  the  end  thrust  by  the  use  of  an  additional 
piston  C.  It  can  be  seen  that  with  the  addition  of  0  it  makes 
little  difference  where  the  discharge  tank  is  placed,  either  above 
or  below  the  valve,  for  if  there  is  any  back  pressure  it  will  act 
equally  upon  B  and  (7,  but  if  C  were  removed  it  would  act  against 
B  only.  When  the  discharge  tank  can  be  placed  on  a  level  with 
the  valve,  nothing  is  gained  by  adding  piston  C. 

HOW  TO  PACK  HYDRAULIC  VERTICAL  CYLINDER 
ELEVATORS. 

Packing  Otis  Vertical  Piston  from  bottom*  —  Remove  the 
top  stop-button  on  hand  rope  and  run  the  car  up  until  the  pis- 
ton strikes  the  bottom  head  in  cylinder.  Secure  the  car  in  this 
position  by  passing  a  strong  rope  under  the  girdle  or  cross- 
head  and  over  the  sheave  timbers.  When  secured,  close  the 
gate  valve  in  the  supply  pipe,  open  the  air  cock  at  the  head  of 
the  cylinder,  and  throw  the  operating  valve  for  the  car  to  go  up. 
Also  open  the  valve  in  the  drain  pipe  from  the  side  of  the  cylin- 
der, and  from  the  lower  head  of  the  cylinder,  thus  allowing  the 
water  to  drain  out  of  the  cylinder.  When  the  cylinder  is  empty, 
throw  the  valve  for  the  car  to  descend  in  order  to  drain  the  wa- 
ter from  the  circulating  pipe.  In  case  of  tank  pressure,  where 
level  of  water  in  lower  tank  is  above  the  bottom  of  the 
cylinder,  the  gate  valve  in  the  discharge  pipe  will  have  to  be 
closed  as  soon  as  the  water  in  the  cylinder  is  on  a  level  with  that 


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1013 


Fig.  155.    Plunger  Elevator  with  Hand  Rope  Control* 


1014 


HANDBOOK    ON    ENGINEERING. 


of  the  tank,  allowing  the  rest  to  pass  through  the  drain  pipe  to 
the  sewer.  When  the  water  is  all  drained  off,  remove  the  lower 
head  of  the  cylinder,  and  the  piston  will  be  accessible.  Remove 
the  bolts  in  the  piston  follower  by  means  of  the  socket  wrench, 
which  is  furnished  for  that  purpose.  Before  removing  the  piston 
head,  mark  its  exact  position,  then  there  will  be  no  difficulty  in 
replacing  it ;  also  be  careful  and  not  let  the  piston  get  turned  in 
the  cylinder,  so  as  to  twist  the  piston  rods.  On  removing  the 
piston  follower,  you  will  find  a  leather  cup  turned  upwards,  with 
coils  of  |-inch  square  duckpacking  on  the  outside.  This  you  will 
remove  and  clean  out  the  dirt ;  also  clean  out  the  holes  in  the 


Fig.  456.     Valve  for  Plunger  Elevator  with  Hand  Rope  Control. 

piston,  through  which  the  water  acts  upon  the  cups.  If  the 
leather  cup  is  in  good  condition,  replace  it,  and  on  the  outside 
place  three  new  coils  of  |-inch  square  duck  packing,  being  careful 
that  they  break  joints  and  also  that  the  thickness  of  the  three  coils 
up  and  down  does  not  fill  the  space  by  J  inch,  as  in  such  case 
the  water  might  swell  the  packing  sufficiently  to  cramp  it  in  this 
space,  thus  destroying  its  power  to  expand.  If  too  tight,  strip 
off  a  few  thicknesses  of  canvas.  Replace  the  piston  follower  and 
cylinder  head,  and  the  cylinder  is  ready  to  refill.  Close  the 
valves  in  the  drain  pipes,  leave  the  air  cock  open  at  the  head  of 
the  cylinder  and  the  operating  valve  in  the  position  to  descend, 
and  open  gate  valve  in  the  discharge.  Slowly  open  the  gate  valve 


HANDBOOK    ON    ENGINEERING.  1015 

in  the  supply  pipe,  allowing  the  cylinder  to  fill  gradually  and  the 
air  to  escape  at  the  head  of  the  cylinder.  When  the  cylinder  is 
I  full  of  water,  leave  the  air  cock  open  and  put  the  operating  valve 
on  the  center.  The  car  can  then  be  untied,  the  stop  button  can 
be  reset,  and  the  elevator  is  ready  to  use.  Make  a  few  trips  be- 
fore closing  the  air  valve. 

Packing  vertical  cylinder  piston  from  top*  —  Run  the  car  to 
the  bottom  and  close  the  gate  valve  in  the  supply  pipe.  Open 
the  air  cock  at  the  head  of  the  cylinder,  and  also  keep  open  the 
valve  in  the  drain  pipe  from  the  side  of  the  cylinder  long  enough 
to  drain  the  water  in  the  cylinder  down  to  the  level  of  the  top 
of  the  piston.  Now  remove  the  top  head  of  the  cylinder,  slipping 
it  and  the  piston  rods  up  out  of  the  way,  and  fasten  there.  If 
the  piston  is  not  near  enough  to  the  top  of  the  cylinder  to  be 
accessible,  attach  a  rope  or  small  tackle  to  the  main  cables 
(not  the  counter-balance  cables)  a  few  feet  above  the  car,  and 
draw  them  down  sufficiently  to  bring  the  piston  within  reach. 
Remove  the  bolts  in  the  piston  follower  by  means  of  the  socket 
wrench  furnished  for  that  purpose.  Mark  the  exact  position 
of  the  piston  follower  before  removing  it,  so  that  there  will  be 
no  difficulty  in  replacing  it.  On  removing  the  piston  follower 
you  will  find  a  leather  cup  turned  upwards,  with  coils  of  |-inch 
square  duck  packing  on  the  outside.  This  you  will  remove  and 
clean  out  the  dirt ;  also  clean  out  the  holes  in  the  piston  through 
which  the  water  acts  upon  the  cup.  If  the  leather  cup  is  in 
good  condition,  replace  it,  and  on  the  outside  place  three  new 
coils  of  |-inch  square  duck  packing,  being  careful  that  they 
break  joints,  and  also  that  the  thickness  of  the  three  coils  up 
and  down  does  not  fill  ths  space  by  £  inch,  as  in  such  case  the 
water  might  swell  the  packing  sufficiently  to  cramp  it  in  this 
space,  thus  destroying  its  power  to  expand.  If  too  tight,  strip 
off  a  few  thicknesses  of  canvas.  Replace  the  piston  follower  and 
let  the  piston  down  to  its  right  position.  Replace  the  cylinder 


1016  HANDBOOK    ON    ENGINEERING. 

head  and  gradually  open  the  gate  valve  in  the  supply  pipe,  first 
being  sure  that  the  operating  valve  is  on  the  down  stroke  or  it  is 
so  the  car  is  coming  down.  As  soon  as  the  air  has  escaped  be- 
fore closing  the  air  cock  to  make  sure  the  air  is  all  out  of  the 
cylinder,  make  a  few  trips,  and  the  elevator  is  ready  to  run. 

Packing  the  vertical  cylinder  valves.  —  To  pack  the  valve, 
run  the  car  to  the  bottom  and  close  the  gate  valve  in  the  supply 
pipe.  Then  throw  the  operating  valve  for  the  car  to  go  up,  open 
the  air  cock  at  the  head  of  the  cylinder  and  the  valve  in  the  drain 
pipe  at  the  bottom,  and  the  water  will  drain  out  of  the  cylinder. 
When  the  cylinder  is  empty,  reverse  the  valve  for  the  car  to  run 
down  so  as  to  let  the  water  out  of  the  circulating  pipe.  In  cases 
of  tank  pressure,  where  the  level  of  the  water  in  the  lower  tank  is 
above  the  bottom  of  the  cylinder,  the  gate  valve  in  the  discharge 
pipe  will  have  to  be  closed  as  soon  as  the  water  in  the  cylinder  is 
on  a  level  with  that  in  the  tank,  allowing  the  rest  to  pass  through 
the  drain  pipe  to  the  sewer.  As  soon  as  the  water  has  all  drained 
off,  take  off  the  valve  cap  and  remove  the  pinion  shaft  and  sheave, 
marking  the  position  of  the  sheave  and  the  relation  which  the 
teeth  on  the  pinion  bear  to  the  teeth  on  the  rack  before  removing. 
You  can  now  take  out  the  valve  plunger  and  put  the  new  cup 
leather  packings  on  in  the  same  position  as  you  find  the  old  ones. 
Replace  all  the  parts  as  first  found.  Before  refilling  the  cylinder, 
close  the  valves  in  the  drain  pipes,  but  leave  the  air  cock  at  the 
head  of  the  cylinder  open  and  be  careful  that  the  operating  valve 
is  in  position  for  the  car  to  go  down.  Gradually  open  the  gate 
valve  in  the  supply  pipe.  When  the  cylinder  has  filled  with  water 
and  the  air  has  escaped,  close  the  air  cock  and  open  the  gate 
valve  in  the  discharge  pipe. 

Packing  piston  rods* — Close  the  gate  valve  in  the  supply 
pipe.  Remove  the  followers  and  glands  to  the  stuffing  boxes 
and  clean  out  the  old  packing.  Repack  with  about  eight  turns  of 


HANDBOOK   ON    ENGINEERING.  1017 

J-inch  flax  packing  to  each  rod,  and  replace  glands  and  followers.. 
Screw  down  the  followers  only  tight  enough  to  prevent  leaking. 

If  traveling  or  auxiliary  sheave  bushing  is  worn  so  that  sheave 
binds,  or  the  bushing  is  nearly  worn  through,  turn  it  half  round, 
and  thus  obtain  a  new  bearing.  If  it  has  been  once  turned  put 
in  a  new  bushing.  See  that  the  piston  rods  draw  alike.  If  they 
do  not,  it  can  be  discerned  by  trying  to  turn  the  rods  with  the 
hand,  or  by  a  groaning  noise  in  the  cylinder.  However,  this 
groaning  may  also  be  caused  by  the  packing  being  worn  out,  in 
which  case  the  car  would  not  stand  stationary.  See  that  all  sup- 
ports remain  secure  and  in  good  condition. 

WATER  FOR  USE  IN  HYDRAULIC  ELEVATORS. 

In  hydraulic  elevator  service  little  heed  is  usually  given  to  the 
quality  of  water,  with  which  the  system  is  operated.  Much  loss 
of  power  by  friction  and  many  dollars  spent  annually  in  repairs 
can  be  avoided  by  a  little  thought  and  action  on  this  subject.  In 
order  to  prove  the  truth  of  this  statement,  one  has  only  to  obtain 
two  samples  of  water,  one  of  soft  water  and  the  other  of  what 
is  commonly  known  as  hard  water.  For  example,  take  rain 
water  as  the  first  sample  and  water  from  the  well  as  the  second. 
Now  rub  your  hands  briskly  together  while  holding  them  im- 
mersed in  one,  and  then  in  the  other  of  these  samples.  You 
will  instantly  realize  that  the  quality  of  water  used  in  elevator 
service  has  much  to  do  with  the  efficiency  of  the  hydraulic  ma- 
chinery. Water  from  the  service  pipes  of  the  oity  water-works 
always  contains  more  or  less  sand  and  other  gritty  substances 
in  suspension,  and  this  grit  acts  much  the  same 'on  the  packing 
and  metal  parts  of  the  apparatus  as  does  a  sand  blast.  Some 
engineers,  having  realized  the  evil  effects  of  water  in  the  state 
that  is  generally  used  have  attempted  to  remedy  the  matter  by 
replacing  the  water  which  is  lost  by  leakage  or  evaporation  by  the 


1018  HANDBOOK    ON    ENGINEERING. 

addition  of  the  water  which  is  discharged  from  the  steam  traps  of 
the  plant;  and  as  this  has  been  distilled,  it  is  almost  chemically 
pure — thus  the  man  who  uses  distilled  water  in  an  elevator  sys- 
tem instead  of  the  water  containing  grit,  is  simply  getting  out  of 
one  difficulty  into  another. 

It  is  a  well-known  fact  in  chemistry  that  pure  water  is  a  solvent 
for  every  known  substance,  and  will  especially  attack  iron  to  a 
large  degree.  Whenever  it  is  practicable,  the  water  for  elevator 
use  should  be  passed  through  a  filter  to  remove  grit  before  being 
allowed  to  pass  into  the  surge  tank.  In  many  cases,  however,  it 
would  be  difficult  for  the  engineer  to  convince  the  owner  of  the 
advisability  of  buying  and  installing  a  filter  for  this  purpose.  A 
simple  and  somewhat  inexpensive  remedy  is  within  reach  of  all  — 
the  plentiful  use  of  soap  will  obviate  many  of  the  evil  effects  of 
hardness  of  the  water,  will  double  the  life  of  the  packing,  will 
reduce  the  loss  by  friction,  and  will,  to  a  large  extent,  prevent 
the  chattering  of  the  pistons,  making  the  elevators  run  much 
smoother.  In  laboratory  practice,  the  degree  of  hardness  or 
softness  of  water  is  determined  by  the  amount  of  pure  soap  that 
is  necessary  to  mix  with  the  water  to  form  a  lather,  or  to  precip- 
itate a  certain  quantity  of  carbonate  of  lime  and  other  substances. 
This  same  action,  on  a  larger  scale,  takes  place  when  soap  is  in- 
troduced into  an  elevator  tank,  and  while  the  oily  portion  of  the 
soap  forms  an  emulsion  with  the  water,  of  great  lubricating 
properties,  the  gritty  matter  is  precipitated  and  can  be  gotten  rid 
of  through  means  of  a  blow-off  in  the  bottom  of  the  tank.  The 
cheapest  and  most  convenient  form  in  which  to  obtain  soap  for 
this  purpose,  is.  the  soap  powder  extensively  manufactured  by 
various  firms  and  which  can  be  purchased  for  about  four  cents 
per  pound.  In  a  plant  of  six  elevators,  with  usually  a  strong 
capacity  of  some  8,000  gallons,  it  is  a  good  practice  to  use  about 
twenty  pounds  of  this  soap  each  week.  The  soap  should  be  at 
first?  dissolved  in  about  ten  times  its  weight  of  boiling  water,  and 


HANDBOOK   ON    ENGINEERING.  1019 

when  cold  it  will  form  a  stiff  soft  soap.  The  practice  of  putting 
in  the  refuse  oil  collected  from  the  drip  pans  is  of  little  value ;  it 
will  not  mix  with  the  water,  but  floats  on  the  surface.  It  rarely 
gets  low  enough  to  enter  the  suction  pipes  of  the  pumps,  and  has 
little  or  no  tendency  to  precipitate  the  solid  matter  that  is  held  in 
suspension  in  the  water. 

If  car  settles,  the  most  probable  cause  is  that  the  valve  or  pis- 
ton needs  repacking.  If  packing  is  all  right,  then  the  air  valve 
in  the  piston  does  not  properly  seat.  If  the  car  springs  up  and 
down  when  stopping,  there  is  air  in  the  cylinder.  When  there  is 
not  much  air,  it  can  often  be  let  out  by  opening  the  air  cock  and 
running  a  few  trips,  but  when  there  is  considerable  air,  run  the 
car  to  near  the  bottom,  placing  a  block  underneath  for  it  to  rest 
upon,  then  place  the  valve  for  the  car  to  descend.  While  in  this 
position,  openthe  air  cock  and  allow  the  air  to  escape.  This  may 
have  to  be  repeated  several  times  before  the  air  is  all  removed. 

Keep  the  cylinder  and  connections  protected  from  frost. 
Where  exposed,  the  easiest  way  to  protect  the  cylinder  is  by  an 
air-tight  box,  open  at  the  bottom,  to  which  point  keep  a  gas  jet 
burning  during  cold  weather.  Where  there  is  steam  in  the  build- 
ing, run  a  coil  near  the  cylinder.  Keep  stop  buttons  on  hand 
cable  properly  adjusted,  so  that  the  car  will  stop  at  a  few  inches 
beyond  either  landing,  before  the  piston  strikes  the  head  of  the 
cylinder.  Regulate  the  speed  desired  for  the  car  by  adjusting 
the  back  stop  buttons,  so  that  the  valve  can  only  be  opened 
either  way  sufficiently  to  give  this  speed.  Occasionally  try  the 
governor  to  see  that  it  works  properly.  Keep  the  machinery 
clean  and  in  good  order. 

ELEVATOR  INCLOSURES  AND  THEIR  CARE. 

Elevator  inclosures,  while  intended  for  protection  to  passen- 
gers, are  often  carelessly  neglected  and  are  often  a  source  of 


1020  HANDBOOK    ON   ENGINEERING. 

danger,  unless  looked  after  and  taken  care  of  in  a  proper  manner. 
It  is  of  the  utmost  importance  that  no  projection  of  any  kind 
shall  extend  into  the  doorways  for  clothing  of  passengers  to 
catch  on,  thus  endangering  their  lives.  The  doors  should  move 
freely  to*  insure  their  action  at  the  touch  of  the  operator.  See 
that  all  bolts  and  screws  are  tight,  and  replace  at  once  all  that 
fall  out,  otherwise,  the  doors  and  panels  may  swing  into  the  path 
of  the  elevator  cage  and  be  torn  off,  and  probably  injure  some 
one,  thus  placing  the  owner  liable  to  damages.  Elevator  doors 
that  are  automatic  in  their  closing  are  the  best,  but  all  operators 
should  be  held  strictly  responsible  for  accidents  occurring  from 
the  carelessness  of  leaving  doors  open.  All  inclosures  should  be 
equipped  with  aprons  above  the  doors  to  the  ceiling  and  as  close 
to  the  cage  as  possible,  to  prevent  passengers  from  falling  out  or 
extending  their  person  through  to  be  caught  by  ceilings  or  beams 
in  the  elevator  shaft.  As  a  rule,  proprietors  of  buildings  take  a 
pride  in  keeping  their  inclosures  and  cars  in  a  neat  condition,  as 
they  are  considered  an  ornament  to  the  building  for  the  purpose 
for  which  they  are  intended,  and  no  expense  is  spared  in  the 
line  of  art ;  so  it  is  recommended  that  they  be  kept  free  from 
dampness.  Dust  with  a  feather  duster  and  use  soft  rags  for 
cleaning.  Never  use  any  gritty  substance,  soaps  or  oils.  II 
they  become  damaged,  have  the  maker  repair  and  relacquer  them. 


HANDBOOK    ON    ENGINEERING. 


1021 


STANDARD  HOISTING  ROPE  WITH  19  WIRES 
TO  THE  STRAND. 

IRON. 


0 

fc 

0) 

I 

Diameter. 

Circumfer- 
ence 
in  inches. 

Weight  per 
foot  in  Ibs. 
of  rope 
with  hemp 
center. 

Breaking 
strain  in 
tons  of 
2000  Ibs. 

f 
Proper 
working 
load  in  tons 
of 
2000  Ibs. 

Circumfer- 
ence of  new 
Manilla 
rope  of 
equal 
strength. 

Minimum 
size  of 
drum  or 
sheave  in 
feet. 

1 

24 

61 

8.00 

74 

15 

14 

13 

2 

2 

6 

6.30 

65 

13 

13 

12 

3 

11 

54 

5.25 

54 

11 

12 

10 

4 

II 

5 

4.10 

44 

9 

11 

84 

5 

14 

41 

3.65 

39 

8 

10 

74 

54 

U 

« 

3.00 

33 

64 

9* 

7 

6 

14 

4 

2.50 

27 

54 

84 

64 

7 

H 

34 

2.00 

20 

4 

74 

6 

8 

i 

3* 

1.58 

16 

3 

64 

5J 

9 

i 

21 

1.20 

11-50 

24 

54 

44 

10 

1 

24 

0.88 

8.64 

U 

41 

4 

104 

i 

2 

0.66 

5.13 

14 

31 

34 

10£ 

ft 

If 

0.44 

4.27 

1 

34 

21 

101 

4 

14 

0-35 

3.48 

4 

3 

24 

lOa 

ft 

U 

0.29 

3.00 

I 

21 

2 

10i 

14 

0.26 

2.50 

4 

24 

14 

1 

Operating  Cable  or  Tiller  Rope,  1  in.  diam.;  |  in.  diam.;  £  in.  diam.; 
|  in.  diam. 

Cables,  and  how  to  care  for  them.  —  Wire  and  hemp  ropes 
of  same  strength  are  equally  pliable.  Experience  has  demonstrated 
that  the  wear  of  wire  cables  increases  with  the  speed.  Hoisting 
ropes  are  manufactured  with  hemp  centers  to  make  them  more 
pliable.  Durability  is  thereby  increased  where  short  bending 
occurs.  All  twisting  and  kinking  of  wire  rope  should  be  avoided. 
Wire  rope  should  be  run  off  by  rolling  a  coil  over  the  ground 
like  a  wheel.  In  no  case  should  galvanized  rope  be  used  for 
hoisting  purposes.  The  coating  of  zinc  wears  off  very  quickly 


1022  HANDBOOK    ON    ENGINEERING. 

and  corrosion  proceeds  with  great  rapidity.  Hoisting  cables 
should  not  be  spliced  under  any  circumstances.  All  fastenings 
at  the  ends  of  rope  should  be  made  very  carefully,  using  only 
the  best  babbitt.  All  clevises  and  clips  should  fit  the  rope 
perfectly.  Metal  fastenings,  where  babbitt  is  used,  should  be 
warmed  before  pouring,  to  prevent  chilling.  Examine  wire  ropes 
frequently  for  broken  wires.  Wire  hoisting  ropes  should  be  con- 
demned when  the  wires  (not  strands)  commence  cracking.  Keep 
the  tension  on  all  cables  alike.  Adjust  with  draw-bars  and  turn- 
buckles  provided. 

Leather  cup  packings  for  valves*  — Leather  for  cups  should 
be  of  the  best  quality,  of  an  even  thickness,  free  from  blemish 
and  treated  with  a  water-proof  dressing.  The  cups  should  be 
of  sufficient  stiffness  to  be  self-sustaining  when  passing  over  per- 
forated valve  lining.  When  ordering  cups,  the  pressure  of  water 
carried  should  be  specified,  aa  the  stiff  cups  intended  for  high- 
pressure  would  not  set  out  against  the  valve  lining  when  low 
pressure  is  used. 

Water*  —  Water  for  use  in  hydraulic  elevators  should  be  per- 
fectly clear  and  free  from  sediment.  A  strainer  should  be  placed 
on  the  supply  pipe  and  water  changed  every  three  months,  and 
the  system  washed  and  flushed. 

Closing  down  elevators*  —  If  an  elevator  is  to  be  shut  down 
for  an  indefinite  period,  run  the  car  to  the  bottom  and  drain  off 
the  water  from  all  parts  of  the  machine ;  otherwise,  a  freeze  is 
likely  to  burst  some  part  of  the  machinery.  If  the  machine  is  of 
the  horizontal  type,  grease  the  cylinder  with  a  heavy  grease ;  if 
vertical,  the  rods  should  be  greased.  Oil  cables  with  raw  linseed 
oil. 


HANDBOOK    ON   ENGINEERING.  1023 


LUBRICATION  FOR  HYDRAULIC  ELEVATORS. 

The  most  effectual  method  of  lubricating  the  internal  parts  of 
hydraulic  elevator  plants  where  pump  and  tanks  are  used,  is  to 
carry  the  exhaust  steam  drips  from  the  foot  of  the  pump  exhaust 
pipe  to  the  discharge  tank,  thus  saving  the  distilled  water  and 
cylinder  oil.  This  system  is  invaluable  when,  water  holding  in 
solution  minerals  is  used,  as  these  minerals  greatly  increase  cor- 
rosion. Horizontal  machines  operated  by  city  pressure  are  best 
lubricated  with  a  heavy  grease  applied  either  mechanically  or  by 
means  of  a  piece  of  waste  on  the  end  of  a  pole.  The  former 
method  serves  as  a  constant  lubricator,  while  in  the  latter  case, 
greasing  is  often  neglected,  and  in  consequence  packing  lasts  but 
a  short  time. 

Lubrication  of  cables*  —  A  good  compound  for  preservation 
and  lubrication  of  cables  is  composed  of  the  following :  Cylinder 
oil,  graphite,  tallow  and  vegetable  tar,  heated  and  thoroughly 
mixed.  Apply  with  a  piece  of  sheepskin  with  wool  inside.  To 
prevent  wire  rope  from  rusting,  apply  raw  linseed  oil. 

Lubrication  of  guides*  —  Steel  guides  should  be  greased  with 
good  cylinder  oil.  Grease  wood  strips  with  No.  3  Albany  grease 
or  lard  oil.  Clean  guides  twice  a  month  to  prevent  gumming. 

Lubrication  of  over  head  sheave  boxes*  —  In  summer  use  a 
heavy  grease.  In  winter  add  cylinder  oil  as  required. 

USEFUL  INFORMATION. 

To  find  leaks  in  elevator  pressure  tanks  in  which  air  is  con- 
fined, paint  round  the  rivet  heads  with  a  solution  of  soap  and  the 
leak  will  be  found  wherever  a  bubble  or  suds  appear.  To  ascer- 
tain the  number  of  gallons  in  cylinders  and  round  tanks,  multi- 
ply the  square  of  diameters  in  inches  by  the  height  in  inches 
and  the  product  by  .0034=gallons.  Weight  of  round  wrought 


1024 


HANDBOOK    ON    ENGINEERING. 


iron  :  Multiply  the  diameter  by  4,  square  the  product  and,  divide 
by  6=the  weight  in  pounds  per  foot.  To  find  the  weight  of  a 
casting  from  the  weight  of  a  pine  pattern,  multiply  one  pound  of 
pattern  by  16.7,  for  cast-iron,  and  by  19  for  brass.  Ordinary 
gray  iron  castings  =  about  4  cubic  inches  to  the  pound. 

"Water* — A  gallon  of  water  (U.  S.  Standard)  contains  231 
cu.  in.  and  weighs  8^  Ibs.  A  cubic  foot  of  water  contains  7£  gal. 
or  1728  cu.  in.  and  weighs  62.425  Ibs.  A  "  Miner's  inch  "  is  a 
measure  for  the  flow  of  water  and  is  the  amount  discharged 
through  an  opening  1  inch  square  in  a  plank  2  in.  in  thickness, 
under  a  head  of  6  in.  to  the  upper  edge  of  the  opening ;  and  this 
is  equal  to  11.625  U.  S.  gal.  per  minute.  The  height  of  a 
column  of  fresh  water,  equal  to  a  pressure  of  1  Ib.  per  sq.  in.,  is 
2.304  feet.  A  column  of  water  1  ft.  high  exerts  a  pressure  of  .433 
Ibs.  per  sq.  in.  The  capacity  of  a  cylinder  in  gallons  is  equal  to 
the  length  in  inches  multiplied  by  the  area  in  inches,  divided  by 
231  (the  cubical  contents  of  one  U.  S.  gal.  in  inches).  The 
velocity  in  feet  per  minute,  necessary  to  discharge  a  given  volume 
of  water  in  a  given  time,  is  found  by  multiplying  the  number  of 
cu.  ft.  of  water  by  144  and  dividing  the  product  by  the  area  of 
the  pipe  in  inches. 

Decimal  Equivalents  of  an  Inch. 


1-16 

1-8 

3-16 

1-4 

5-16 

3-8 

7-16 

1-2 

.0625 

.125 

.1875 

.25 

.3125 

.375 

.4375 

.5 

9-16 

5-8 

11-16 

3-4 

13-16 

7-8 

15-16 

.6625 

.625 

.6875 

.75 

.8125 

.875 

.9375 

HANDBOOK    ON    ENGINEERING.  1025 


ELEVATOR  SAFETIES. 

All  types  of  elevators  in  which  the  car  ia  lifted  by  cables  are 
provided  with  means  for  arresting  the  movement  of  the  car  if  it 
attains  a  dangerously  high  speed  through  the  breaking  of  the 
lifting  ropes  or  the  disarrangement  of  any  part  of  the  hoisting 
apparatus.  The  direct  plunger  elevators  are  not  provided  with 
safety  appliances,  it  being  considered  that  the  plunger  on  which 
the  car  is  lifted  will  prevent  the  latter  from  dropping,  as  it  cannot 
be  crushed  by  the  load,  nor  caused  to  run  down  any  faster  than 
the  water  can  escape  from  the  cylinder. 

In  the  early  days  of  elevators,  when  the  car  speed  was  low,  the 
safety  devices  consisted  of  racks  attached  to  the  faces  of  the 
guides,  and  dogs  carried  by  the  car,  these  dogs  being  held  out  of 
action  so  long  as  the  ropes  did  not  break.  With  the  gradual  in- 
crease in  height  of  buildings,  the  car  speed  was  increased  and 
then  it  was  realized  that  the  rack  and  dog  devices  were  not  adapt- 
ed to  do  the  work,  as  they  would  stop  the  car  so  suddenly  as  to 
give  the  passengers  nearly  as  bad  a  shaking  up  as  they  would  re- 
ceive if  the  car  went  to  the  bottom  of  the  well.  For  the  purpose 
of  producing  a  more  gradual  stoppage  of  the  car,  wedge  safety 
devices  were  introduced.  .  These  safeties  act  by  forcing  a  wedge 
between  the  guides  on  which  the  car  runs  and  strong  iron  jaws 
carried  by  the  car,  and  as  the  wedges  are  tightened  slowly,  the 
car  can  run  some  distance  before  it  is'  stopped,  thus  producing  a 
gradual  stop.  The  jaws  that  hold  the  clamping  wedge  are 
fastened  to  the  ends  of  a  massive  hard  wood  plank,  and  for  this 
reason  the  apparatus  was  called  a  "  Safety  Plank,  "  and  is  known 
by  that  name  at  the  present  time. 

A  wedge  safety  plank,  of  the  type  used  by  the  Otis  elevator  Co. , 
is  shown  in  Figs.  457,  458,  459,  the  last  two  illustrations  only 
show  one  end  of  the  apparatus.  This  device  is  used  in  connec- 


1026 


HANDBOOK    ON    ENGINEERING. 


tion  with  four  lifting  cables  two  of  which  are  secured  to  the  ends 
A  B  of  a  rocker  (7, 'the  other  two  being  similarly  connected  with 


a  rocker   at  the  other  end.     The  rocker   G  has    projections  that 
move  levers  mounted  on  shaft  H,  and  one  of  these  levers,  marked 


HANDBOOK   ON    ENGINEERING.  1027 


5,  when  raised  strikes  wedge  ^and  forces  it  up  between  the  jaw? 
of  the  safety  plank  and  the  guide  M.  The  end  of  b  is  sharp  and 
long  enough  to  reach  the  guide  and  cut  into  it,  thus  helping  to 
force  the  wedge  up  tight  enough  to  hold  the  car.  If  one  of  the 
lifting  cables  attached  to  the  ends  A  B  of  rocker  C  should  break, 
that  end  of  C  will  drop  and  then  shaft  H  will  be  rotated  so  as  to 
swing  b  upward  and  force  the  wedge  JVinto  action.  The  rocker 
C  has  two  projections,  one  on  each  side  of  H  so  that  no  matter 
which  way  C  is  tilted,  b  will  be  moved  upward. 

If  elevators  dropped  only  when  the  ropes  break,  the  safety  as 
explained  would  be  sufficient,  but  as  a  matter  of  fact,  they  can- 
not very  well  drop  in  this  way,  because  all  the  cables  will  not 
break  at  the  same  time.  In,  nearly  every  case,  the  elevator  does 
not  actually  drop,  but  through  some  disarrangement  of  the  ma- 
chinery it  attains  a  dangerously  high  speed,  that  is,  it  runs  away. 
Owing  to  this  fact  it  is  necessary  to  arrange  the  safeties  so  that 
they  will  act  if  the  car  speed  becomes  too  great,  regardless  of 
what  the  cause  may  be.  This  is  accomplished  by  providing  a 
governor,  similar  to  those  used  on  engines,  that  is  driven  by  the 
car,  and  when  the  speed  becomes  too  great  it  throws  the  safety 
into  action.  The  safety  governor  of  the  Otis  Co.,  is  shown  in 
Fig.  460.  It  is  driven  by  a  rope  that  passes  over  sheave  A  and 
runs  down  in  the  elevator  well  to  the  bottom  where  it  passes  under 
another  sheave.  This  rope  is  fastened  to  the  end  ytoi  lever  G, 
Fig.  458,  and  through  lever  Jc  acts  to  rotate  shaft  H.  The  spring 
S  wound  on  H  is  stiff  enough  to.  drive  the  governor  and  prevent 
If  from  turning,  but  if  the  car  speed  becomes  too  great,  the  rod 
D,  Fig.  460,  will  lift  the  crank  jVand  thus  throw  in  a  clamp  that 
will  hold  the  rope  fast.  When  this  occurs,  the  downward  move- 
ment of  the  car  will  cause  lever  G  to  rotate  shaft  H  and  thus  6 
will  force  the  safety  wedge  N  into  position  to  stop  the  car. 

There  are  many  modifications  of  the  wedge  safety,  but  as  they 
do  not  work  with  certainty  on  iron  guides  they  are  now  practical- 


1028 


HANDBOOK    ON    ENGINEERING. 


ly  out  of  date,  as  wooden  guides  are  not  used  except  in  the  few 
cases  where  they  are  permitted  by  the  insurance  regulations,  or 
where  a  cheap  construction  is  desired.  In  large  fireproof  build- 
ings they  are  not  allowed. 


Tig.  460.    Otis  Safety  Governors  Single  Acting. 

A  modification  of  the  wedge  safety  that  was  used  to  some  ex- 
tent a  few  years  ago  is  shown  in  Figs.  461  and  462,  the  first  giving 
the  position  of  the  parts  when  out  of  action,  and  the  second  the 
position  when  in  action.  This  is  known  as  the  roller  safety.  The 


HANDBOOK   ON   ENGINEERING. 


1029 


roller  a,  when  drawn  up  by  the  lifting  rod,  wedges  between  the 
iron  guide  and  the  jaw  of   the  safety   plank   and  then  rolls  up 


until  it  binds  tight  enough  to  stop   the  car.     The  objection  to 
this  device  is  that  it  grips  too  soon,  in  fact  it  is  liable  to  stop 


HANDBOOK  ON  ENGINEERING. 


the;  car  in  two  or  three  inches,  so  that  if  the  speed  is  high,  the 
passengers  will  get  a  serious  shaking  up.  The  lifting  rod  is 
operated  by  a  safety  governor,  the  connections  with  the  latter 
being  indicated  in  Figs.  463  and  464,  the  first  showing  the  actual 


Fig.  403.    Governor  Rope  Connection  for  Roller  Safely. 

connection  with  the  governor  rope,  and  the  second,  the  levers,  in 
the  top  framing  of  the  car,  to  transmit  the  movement  to  the  op- 
posite side  so  that  both  rollers  may  be  thrown  into  action  at  the 


HANDBOOK    ON    ENGINEERING. 


1031 


same  time.  It  will  be  noticed  in  Fig.  464  that  the  lifting  cables 
are  permanently  secured  to  the  car  framing,  and  not  to  any  part 
of  the  safety,  so  that  if  one  or  two  of  them  should  break,  the 
safety  would  not  go  into  action.  This,  however,  does  not  make 
the  device  any  the  less  effective,  because  the  car  could  not  drop 
unless  all  the  ropes  broke  at  the  same  time,  and  if  this  occurred, 


f^ 

1 

V 

n 

r- 

—  r 

-J 

/. 

i 

,'T 

ij,                  p 

•                I 

^^                               ^ 

>%^                                                     222 

k 

a 

j©^D 

e  j^b 

Iff 

^^& 

JA 

^1L 

Fit?.  464.    Lifting  Rope  Connections  for  Roller  Safety.  '* 

the  speed  would  at  once  increase,  and  then  the  safety  governor 
would  come  into  action  and  throw  the  rollers  up,  just  the  same 
as  if  the  speed  had  increased  from  some  other  cause.  This  type 
of  safety  is  not  used  now  because  it  stops  the  car  too  suddenly. 
A  safety  to  be  satisfactory  must  be  so  arranged  that  it  will 
produce  a  gradual  stop,  if  it  comes  into  action,  This  result  is 


1032 


HANDBOOK    ON    ENGINEERING. 


accomplished  in  the  type  of  safety  commonly  known  as  the  brake 
or  clamp  safety.  It  consists  of  strong  brake  shoes  arranged  to 
press  against  the  sides  of  the  guides  on  which  the  car  runs,  with 
a  continuously  increasing  pressure  until  the  breaking  action  be- 
comes sufficient  to  actually  stop  the  car.  It  can  be  easily  seen 


that  with  such  an  arrangement,  the  effect  is  to  first  reduce  the 
car  velocity  and  then  gradually  bring  it  to  an  actual  stop,  the 
time,  or  distance  in  which  the  car  is  stopped  depending  on  the 
rapidity  with  which  the  braking  force  is  increased.  Two  views 
of  the  Otis  clamp  safety  are  given  in  Figs  465  and  466,  the  first 


HANDBOOK    ON    ENGINEERING.  1033 

being  a  side  elevation  in  section,  and  the    second  a  plan.     The 


Fig.  4C7. 
Governor  Rope  Connection  for  Brake  Safety* 

rope  that  winds  around  the  actuating  drum,  Fig.  465,  ia  attached 


1034  HANDBOOK   ON   ENGINEERING. 

to  the  governor  rope,  in  the  way  clearly  shown  in  Fig.  467.  If 
the  car  speed  becomes  too  great,  the  governor  acts,  and  clarnps 
the  rope,  then  the  drum  rope  unwinds,  and  thus  rotates  the 
drum,  and  the  latter  by  turning  the  right  and  left  hand  nuts 
forces  the  screws  out  and  thus  spreads  the  toggle  links  B  B  Fig. 
466,  and  applies  the  brakes  to  the  guide.  It  is  evident  that  the 
further  the  car  runs  after  the  safety  governor  has  gripped  the 
rope,  the  further  the  actuating  drum  will  be  rotated,  and  as  a 
result  the  more  the  safety  brake  jaws  will  be  forced  against  the 
guides.  By  this  arrangement  the  motion  of  the  car  is  gradually 
arrested,  and  the  passengers  are  not  seriously  jolted.  If  the 
load  in  the  car  is  light,  and  the  guides  are  not  properly  lubricated, 
it  is  possible  for  this  device  to  grip  suddenly,  but  it  can  never  act 
as  suddenly  as  the  roller  safety. 

There  are  several  different  designs  of  these  brake  safeties,  but 
they  are  all  substantially  alike.  The  Morse  and  Williams  design 
is  shown  in  Figs.  468  and  469.  As  will  be  seen  the  diff  erencebe- 
tween  this  and  the  Otis  safety  is  principally  in  the  details  of  con- 
struction of  the  clamping  jaws.  In  the  Otis  design  a  lever  C  is 
provided  that  can  be  moved  by  the  operator  in  the  car,  so  as  to 
either  put  on  the  brake,  or  release  it  after  it  has  caught.  In  the 
Morse  and  Williams  design  this  same  result  is  accomplished 
through  the  beveLgears  shown,  in, Fig.  469,  the  end  M  being 
squared  so  as  to  receive  a  wrench. 

Another  type  of  clamp  safety  is  shown  in  Figsl  470-471-472 
This  is  known  ais  the  "  Pratt  safety."  This  device  has  a  strong 
spring  M  in  addition  to  the  parts  used  in  the  two  previously  ex- 
plained designs*  When  the  safety  is  out  of  action,  this  spring  is 
held  compressed  by  a  catch 'JT, '  as  in  Fig.  470.  When  the  device 
goes  into  action,  the  first  rotation  of  the  drum  and  its  shaft  D 
acts  to  move  ,7  to  one  side  and  releasethe  catch  K  thus  permit- 
ting spring  M  to  throw  the  levers  into  the  position  of  Fig.  471 
and  thereby  to  apply  the  brake  shoes  with  all  the  force  due  to 


HANDBOOK    ON    ENGINEERING, 


1035 


the  tension  of  the  spring.  This  force  is  not  enough  to  stop  the 
car  suddenly,  even  if  lightly  loaded,  but  it  will  retard  the  velocity 
decidedly.  The  continued  rotation  of  the  drum  compresses  spring 
M  and  thus  increases  the  pressure  on  the  brake  shoes  until  the 
car  comes  to  rest,  and  the  safety  assumes  the  position  shown  in 
Fig.  472. 


Fig.  468. 


Fig.  469.    Morse  &  Williams  Brake  Safety 


The  clamp  safety  is  the  only  one  suitable  for  electric  eleva- 
tors because  it  can  be  easily  arranged  so  as  to  act  on  the  up 
as  well  as  the  down  trip  of  the  car.  Electric  elevators  are  almost 
always  arranged  so  that  the  counterbalance  weighs  more  than  the 
car.  As  a  rule  the  counterbalance  weighs  as  much  a,s  thie  car 
and  one  half  of  the  maximum  load,  hence,  if  the  car  runs  up  with* 


1036 


HANDBOOK    ON   ENGINEERING. 


a  light  load,  and  it  runs  away  the  counterbalance  will  run  down 
and  send  the  car  up  to  the  top  of  the  building  at  a  high  velocity. 


jp 

Fig.  470.  Fiff.  471.  Ffe.  472. 

Pratt-Brake  Safety. 

If  the  car  has  a  full  load,  then  it  will  weigh  more  than  the  coun- 
terbalance, and  as  a  result  will  run  down  to  the  bottom  of  the 


HANDBOOK   ON   ENGINEERING.  1037 

well  at  a  high  velocity.  On  this  account  a  safety  to  be  of  any 
value  on  an  electric  elevator  must  be  able  to  act  for  either  direc- 
tion of  motion  of  the  car.  By  looking  at  Fig.  467  it  can  be  seen 
that  to  make  the  clamp  safety  act  in  both  directions,  all  that  is 
necessary  is  to  place  another  sheave  directly  under  A  so  as  to 
hold  the  drum  rope  in  position  when  the  governor  rope  pulls 
down  as  well  as  when  it  pulls  up.  This  is  the  way  in  which  the 
safety  is  arranged  when  used  with  electric  elevators.  The  safety 
governor  in  such  cases  is  made  double  acting,  which  is  accom- 
plished by  providing  rope  clamping  devices  on  both  sides  as 
shown  in  Fig.  473,  which  is  the  double  acting  Otis  safety  governor. 
This  governor  will  clamp  the  rope  regardless  of  which  direction 
it  is  running.  The  levers  shown  on  the  clamping  devices  of  the 
governor  are  for  the  purpose  of  releasing  it  after  it  comes  into 
action. 

In  addition  to  the  safeties  explained  in  the  foregoing,  all 
elevators,  hydraulic  and  electric,  are  provided  with  automatic 
stopping  devices  that  will  stop  the  car  automatically  at  the  top 
and  bottom  landings,  providing  they  are  properly  adjusted,  and 
kept  in  running  order,  and  unless  a  car  attains  a  very  high  vel- 
ocity in  running  away,  these  automatic  stops  will  check  its  speed 
at  the  end  of  its  travel.  Experience,  however,  shows  that  these 
stops  are  often  allowed  to  get  out  of  adjustment  so  that  they 
fail  to  act  properly  when  called  upon.  This  is  also  true  of  the 
safeties  herein  explained.  If  you  want  to  avoid  accidents,  make 
sure  that  the  safeties  and  safety  governor,  and  the  automatic 
stops  are  properly  adjusted,  and  in  perfect  working  order. 
Never  use  a  governor  or  automatic  safety  rope  that  looks  at  all 
worn,  for  when  called  into  action  it  may  break,  and  then  an 
accident  will  follow. 

As  can  be  seen,  if  the  governor  rope  is  not  strong,  it  may  snap 
off  when  the  clamp  grips  it,  and  if  this  occurs,  the  safety  will 
not  act.  The  ropes  used  to  operate  the  hydraulic  automatic 


1038 


HANDBOOK    ON    ENGINEERING. 


stops  are  not  so.  likely  to  break  because  they  come  into  action 
very  often,  hence,  they  are  more  likely  to  show  when  they  are 


Fig-.  473. 
Otis  Double  Acting  Safety  Governor. 

worn  out ;  but  the  automatic  stops    should  be  kept   in  perfect 
adjustment  all  the  time. 

As  the  safeties  seldom  come  into  action,  they  are  liable  to  rust 
up  and  stick,  unless  often  examined,  oiled  up  and  well  cleaned,, 


HANDBOOK? 


1039 


PIPES  AOT  ITAffKS. 
CONTENTS^IN  CUBIC  FEET  AND  IN  UVS.  GALLONS, 

(FROM   TRAUTWINE) 

Of  231  cubic  inches  (or  7.4805  gallons  to  a  cnblc  foot);  and  for  one  foot  of  length  off 
the  cylinder.  For  the  contents  for  a  greater  diameter  than  any  in  the  table  lake. 
quantity  opposite  one-half  said  diameter,  and  multiply  it  by  4.  Thus,  the  number 
.oi  cobic  feet  in  one  foot  length  of  a  pipe  80  inches  in  diameter  is  equal  t$ 
18.728X4=34.912  cubic  feet.  So  also  with  gallons  and  areas. 


8*^ 

For  1  foot  in 

For  1  foot  in 

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.--  —    '     - 

4  •  •'••  '  ~   ^ 

'„.„,.,      * 

1040  HANDBOOK    ON    ENGINEERING. 


CHAPTER   XXXII. 
FRICTION  AND  LUBRICATION. 

BY    WILLIAM    M.    DAVIS. 

Friction  has  been  aptly  described  as  the  "  Highway  robber  of 
mechanical  energy,"  levying  tribute  on  all  matter  in  motion,  ex- 
erting a  retarding  influence  and  requiring  power  to  overcome  it. 

When  one  realizes  that  if  it  were  not  for  the  thin  film  or  layer 
of  oil  between  the  surface  of  the  journals  and  their  bearings  and 
the  constant  supply  of  oil  to  maintain  this  film,  the  largest  loco- 
motive could  not  start  a  heavy  train  or  keep  it  in  motion,  or  the 
most  powerful  marine  engine  could  not  drive  the  ship  a  mile 
without  heating  of  the  bearings,  one  readily  understands  that  a 
knowledge  of  lubrication  and  friction  and  of  the  laws  relating  to 
friction  is  a  very  important  part  of  the  training  of  an  engineer. 

LAWS  OF  FRICTION. 

Friction  is  defined  as  the  resistance  caused  by  the  motion  of  a 
body  when  in  contact  ivith  another  body  that  does  not  partake  of  its 
motion. 

There  are  five  commonly  accepted  and  fundamental  laws  re- 
lating to  the  friction  of  plane  surfaces  in  contact. 

First.  —  Friction  will  vary  in  proportion  to  the  pressure  on  the 
surfaces.  That  is,  increasing  the  pressure  increases  the  friction. 

Second.  —  Friction  is  independent  of  the  areas  of  the  contact 
surfaces  when  the  pressure  and  speed  remain  constant.  But 
distributing  the  pressure  or  friction  over  a  larger  area  renders  the 
liability  of  heating  and  abrasion  less  than  if  the  friction  had  been 
concentrated  on  a  smaller  area. 

Third.  —  Friction  increases  with  the  roughness  of  the  surfaces 
and  decreases  *<»  the  surfaces  become  smoother. 

Fourth.  —  Friction  is  greatest  at  the  beginning  of  motion.  In 
the  effort  to  move  a  body  greater  force  is  required  to  overcome 


HANDBOOK    ON    ENGINEERING.  1041 

the  friction  at  the  instant  of  starting  than  after  motion  has  com- 
menced. 

Fifth.  —  Friction  is  greater  between  soft  bodies  than  between 
hard  bodies. 

These  rules  hold  good  within  certain  limits  but  will  fluctuate 
under  varying  conditions  of  load  and  lubricant,  and  condition  and 
composition  of  the  contact  surfaces. 

Friction  is  always  a  resisting  and  a  retarding  force,  tending  to 
bring  everything  in  motion  to  a  state  of  rest,  and  in  doing  so  re- 
sults in  the  conversion  of  energy  into  heat,  it  has  been  calculated 
that  one  horse  power  or  33,000  foot  pounds  exerted  in  over-com- 
ing friction  results  in  the  conversion  of  energy  into  43  British 
Thermal  Units  of  heat. 

In  the  case  of  machinery  in  motion  the  surfaces  moving  in  con- 
tact have  a  tendency  to  adhere  to  each  other ;  the  minute  pro- 
jections which  exist  on  all  surfaces  to  a  greater  or  less  extent 
(depending  upon  the  hardness  and  smoothness  of  the  surfaces) 
have  a  tendency  to  cling  to  each  other  and  in  order  to  operate 
machinery  without  undue  friction  the  surfaces  must  be  kept 
apart,  something  must  be  used  that  will  flow  or  spread  out  over 
the  surfaces  and  cover  up  these  projections  and  prevent  the  sur- 
faces from  coming  in  direct  contact,  for  which  purpose  lubricants 
of  various  grades  are  used. 

USES  OF  FRICTION. 

Yet,  friction  in  mechanics  has  its  uses ;  it  is  the  friction,  or 
adhesion  (as  it  is  sometimes  called)  of  the  driving  wheels  to  the 
rails  that  enables  a  locomotive  to  start  and  keep  in  motion  a 
heavy  train,  it  is  the  friction  of  the  brake  shoes  on  the  wheels  as 
applied  by  the  air  brakes  that  stops  the  train,  it  is  the  friction  of 
the  belt  on  the  pulley  that  enables  power  to  be  transmitted  from 
one  piece  of  mechanism  to  another. 

Friction  as  it  occurs  in  mechanics  is  what  is  known  as  friction 


1042 


HANDBOOK    ON    ENGINEERING. 


of  solids  and  friction  of  fluids  ;  friction  of  solids  may  be  divided 
into  two  classes,  namely:  rolling  friction,  such  as  a  car  wheel 
rolling  on  a  rail  or  balls  in  a  ball  bearing  ;  and  sliding 

friction,  such  as  a  cross-head  on  the  guide  bars. 

CO-EFFICIENT  OF  FRICTION. 

The  relation  that  thepoiver  required  to  move  a  body  bears  to  the 
weight  or  pressure  on  the  body  is  known  as  the  co-efficient  offrictwn, 
or,  to  put  it  in  another  form,  the  co-efficient  of  friction  is  the 
ratio  between  the  resistance  to  motion  and  the  perpendicular 
pressure,  and  is  determined  by  dividing  the  amount  of  the  former 
by  the  latter. 

One  of  the  simplest  methods  of  demon  strati  ng  graphically  the 
simple  laws  of  friction  of  plane  surfaces  and  the  determination  of 
the  co-efficient  of  friction  is  by  drawing  a  block  of  iron  or  other 
metal  across  a  table  or  an  iron  plate  by  means  of  weights  sus- 
pended to  a  cord  which  is  attached  to  the  block  as  shown  in 
Figs.  1  and  2. 


L*"' 


Fig.  1.     Illustrating  Laws  of  Friction. 


It  is  noticed  that  the  block  is  flat  on  one  side,  and  on  the  other 
side  are  four  small  projections  or  legs,  each  one  square  inch  in 
area,  the  size  of  the  block  is  12  inches  long,  8  inches  wide  and  2 
inches  thick,  and  weighs  50  pounds.  If  we  lay  the  block  with 
its  largest  surface  down  it  will  have  a  surface  contact  with  the 


HANDBOOK    ON    ENGINEERING. 


1043 


table  of  96  square  inches  and  placing  weights  on  the  cord  until 
the  block  commences  to  move  we  find  that  it  requires  a  weight  of 
7  pounds  to  pull  it  across  the  table  ;  now  if  the  block  be  turned 
upside  down  so  that  it  rests  on  the  four  legs  it  will  be  found  that 
it  requires  exactly  the  same  amount  of  force  to  move  the  block 
that  it  had  before. 

As  we  have  found  by  experiment  that  to  move  the  weight  of  50 
pounds  required  a  force  or  pull  of  7  pounds,  the  co-efficient  of 
friction  in  this  case  will  be  found  by  dividing  the  pull  by  the 
weight,  7-r-50=  .14,  or,  to  put  it  in  another  form,  it  will  require 
.14  of  a  pound  of  force  to  move  1  pound  of  weight. 


Fig.  2.    Illustrating  Laws  of  Friction. 

The  second  law  states  that  friction  is  independent  of  the  areas 
of  the  surfaces,  it  has  been  found  by  experiment  that  it  required 
a  pull  of  7  pounds  to  move  the  block  no  matter  which  side  it 
stood  on. 

Let  us  prove  this. 

The  block  when  on  its  largest  side  had  a  surface  contact  of 
8"xl2",  or  96  square  inches  and  exerted  a  pressure  due  to  its 
weight  of  50  Ibs.,  or  .52  of  a  pound  per  square  inch  of  area. 
The  co-efficient  has  been  found  to  be  .14,  then  the  pull  per  square 
inch  of  surface  would  be  .52  x.  14  =  .0729,  which  multiplied  by 
the  total  area,  96  sq.  in.,  will  be  found  to  be  6.9888,  or  practically 
7  pounds. 


1044  HANDBOOK    ON    ENGINEERING. 

Now,  when  the  block  was  reversed  and  stood  on  the  four  legs 
of  1  sq.  in.  each,  the  total  contact  was  only  4  sq.  inches,  but 
the  pressure  (50  pounds),  remained  the  same,  50 -i- 4  =12. 5 
pounds  per  square  inch,  which  multiplied  by  the  co-efficient  .14 
equals  1.75,  then  again  multiplying  this  result  by  4  sq.  in,  again 
gives  a  total  of  7  pounds. 

Thus  it  will  be  seen  that  the  extent  of  surfaces  has  no  influence 
on  the  friction  as  long  as  the  pressure  of  weight  is  constant,  but 
in  machine  design  increasing  the  area  of  surface  contact  allows 
the  total  pressure  to  be  distributed  over  a  greater  area  and  re- 
duces the  liability  of  heating  and  abrading,  or  in  other  words, 
while  the  total  pressure  remains  the  same  the  pressure  per  square 
inch  will  be  less. 


Fig.  3.    Laws  of  Friction. 


Another  method  of  determining  the  co-efficient  of  friction,  or, 
as  it  is  usually  termed,  the  angle  of  friction,  can  be  illustrated  by 
means  of  a  weight  on  an  inclined  plane. 

Place  a  weight  on  a  board  or  other  plane  surface  and  raise  one 
end  slowly  as  in  Fig.  3  until  the  weight  commences  to  slide ;  the 
angle  "a  "  between  the  position  of  the  plane  surface  when  the 
weight  commenced  to  move  and  the  horizontal  is  the  angle  of 
friction,  and  will  vary  with  the  smoothness  of  the  surfaces  and 
the  weight  or  pressure. 

The  angle  of  friction  indicates  the  point  where  the  attraction 
of  gravitation  just  overcomes  the  friction  between  the  surfaces. 

To  find  the  amount  of  power  absorbed  by  friction  multiply  the 
weight  by  the  co-efficient  of  friction,  multiply  the  result  by  the 
velocity  in  feet  per  minute  and  divide  that  by  33,000. 


HANDBOOK    ON    ENGINEERING.  1045 

For  instance,  a  shaft  and  fly  wheel  weighs  8,000  pounds,  sur- 
face travel  of  journals  is  300  feet  per  minute,  the  co-efficient  of 
friction  is  taken  as  being  .04. 

What  would  be  the  horse  power  required  to  run  the  shaft? 
8,000  x. 04x300 

-=2.&09  H.  P. 
33,000 

While  the  co-efficient  of  friction  must  always  be  taken  into 
consideration  when  designing  and  constructing  machinery,  it  is 
not  always  practicable  to  calculate  it  with  any  degree  of  accuracy, 
in  fact  it  can  only  be  determined  absolutely  by  experiment. 

THEORY  OF  LUBRICATION. 

Lubrication  as  it  is  considered  in  mechanics  is  the  application 
or  introduction  of  a  smooth  fluid  substance,  preferably  an  oil, 
between  two  hard  moving  surfaces  that  will  keep  them  from  com- 
ing in  direct  contact. 

Unless  the  surfaces  are  kept  apart  by  some  medium  the  asper- 
ities and  irregularities  which  exist  on  all  surfaces  no  matter  how 
hard  or  smooth,  will  interlock,  and  the  friction  caused  in  tearing 
them  apart  and  wearing  them  down  will  generate  heat. 

The  action  of  a  lubricant  is  to  flow  between  the  close-fitting 
surfaces,  filling  up  the  interstices  and  covering  up  the  high  spots, 
acting  as  a  cushion  and  taking  up  whatever  heat  may  be  gener- 
ated and  carrying  it  off  instead  of  allowing  it  to  be  absorbed  by 
the  wearing  surfaces. 

To  do  this  properly,  a  lubricant  should  have  certain  properties, 
it  should  be  of  a  fluid  nature  so  that  it  will  flow  readily  between 
surfaces  that  are  close-fitting  and  under  heavy  pressure.  It 
should  possess  a  certain  amount  of  cohesiveness,  or  viscosity,  as 
it  is  usually  called. 

By  cohesiveness  is  meant  the  Clinging  together  of  the  molecules 
its  own  particles. 


1046  HANDBOOK    ON    ENGINEERING. 

Oil  should  have  good  adhesive  properties  in  order  that  it  will 
cling  well  to  metallic  surfaces. 

By  adhesion  is  meant  the  tendency  of  a  substance  to  cling  to  other 
substances 

It  should  be  high  in  flash  test  in  order  that  whatever  heat  it  is 
subjected  to  will  not  cause  it  to  give  off  an  inflammable  vapor. 
It  should  have  a  cold  test  of  such  degree  that  it  will  remain  fluid 
at  low  temperatures. 

The  above  requirements  will  be  found  embodied  to  the  greatest 
degree  in  the  various  kinds  of  vegetable,  animal  and  petroleum 
oils. 

The  first  oils  used  in  the  lubrication  of  machinery  were  vegeta- 
ble oils,  such  as  castor  oil,  palm  oil,  and  olive  oil ;  and  animal  oil 
such  as  lard,  neats-foot,  tallow  and  sperm  oils. 

All  these  oils,  while  in  many  respects  excellent  lubricants  are 
not  now  used  to  any  extent  since  the  introduction  of  petroleum  or 
mineral  oils,  for  the  following  reasons :  First.  —  On  account  of 
their  higher  price  as  compared  with  petroleum  oils.  In  recent 
years  the  processes  of  refining  petroleum  have  been  brought  to 
such  a  state  of  perfection  that  they  have  almost  entirely  driven 
the  animal  and  vegetable  oils  from  the  market  as  lubricants  for 
machinery.  Second. — Being  of  organic  origin  they  absorb 
oxygen  from  the  atmosphere,  and,  in  time,  become  rancid,  thick 
and  gummy.  These  oils  are  of  very  poor  cold  test,  congealing  at 
a  comparatively  high  temperature,  thus  making  them  inconvenient 
for  use  in  cold  weather. 

Petroleum  oils  have  many  advantages  as  lubricants  over  ani- 
mal or  vegetable  oils.  First.  —  Is  their  cheapness.  Second.  — • 
Being  of  non-organic  origin  they  do  not  change  their  condition, 
do  not  become  rancid,  thick  or  gummy  by  constant  exposure  to 
the  air,  and  have  no  corrosive  action  on  metals.  Third.  —  By 
what  is  known,  as  fractional  distillation  they  can  be  separated  into 
a  great  many  different  grades,  from  the  lightest  spindle  oils  to 


HANDBOOK    ON    ENGINEERING.  1047 

the  dense  heavy  cylinder  oils.  Fourth.  — They  are  of  lower  cold 
test  and  there  is  not  the  liability  of  spontaneous  combustion  as 
with  animal  oils. 

The  engineer  in  charge  of  a  plant  will  find  on  the  market  a 
wide  range  of  petroleum  lubricants  to  choose  from  to  meet  the 
various  conditions  which  will  arise  in  the  proper  lubrication  of 
his  machinery. 

The  conditions  which  produce  the  greatest  differences  in  ordi- 
nary lubrication  are  the  nature  and  quality  of  the  lubricant,  the 
nature  and  condition  of  the  wearing  surfaces,  the  speed  and 
pressure  and  the  temperature. 

Variations  of  friction  of  lubricated  surfaces  occur  with  every 
change  of  condition  of  either  the  bearing  or  journal  surfaces,  or 
of  the  lubricant  applied  to  them. 

The  ordinary  facilities  of  the  engine  room  do  not  usually  afford 
means  to  make  elaborate  tests  of  the  co-efficient  of  friction  of 
various  oils,  nor  would  such  tests  be  of  any  practical  value  to  an 
engineer,  as  they  can  only  be  made  with  any  degree  of  accuracy 
on  expensive  testing  machines  built  expressly  for  this  purpose, 
which  are  very  little  used  except  in  the  laboratories  of  the  techni- 
cal schools  and  the  testing  rooms  of  a  few  of  the  large  railroad 
companies  and  manufacturers  of  oils. 

But  an  engineer  can  often  make  valuable  comparative  tests  of 
different  grades  of  oil  on  the  ordinary  machinery  of  the  engine 
room  ;  for  instance,  a  difference  between  two  oils  of  several  de- 
grees in  the  temperature  of  a  bearing  of  an  engine  or  a  dynamo 
may  be  detected  by  means  of  a  thermometer  placed  in  the  bear- 
ing, with  the  bulb  resting  on  the  shaft  or  immersed  in  the  oil 
chamber. 

In  tests  of  this  kind  care  must  be  taken  that  the  rate  of  oil 
feed,  the  belt  tension,  the  pressure  on  the  bearings  and  the  speed 
remain  constant ;  an  allowance  should  also  be  made  for  any  dif- 
ference in  the  temperature  of  the  room  during  the  tests. 


1048  HANDBOOK    ON    ENGINEERING. 

Some  day,  engine  builders  will  equip  the  main  bearings  of 
their  engines  with  thermometers  so  that  the  temperature  can  be 
noted,  the  engineer  will  then  be  able  to  see  at  a  glance  whether 
the  temperature  is  above  the  normal  or  not,  in  the  same  way  as 
he  notes  the  temperature  of  his  feed  water  by  means  of  a  ther- 
mometer in  the  boiler  feed  pipe ;  of  course,  an  engine  bearing 
from  lack  of  oil,  stoppage  of  the  oil  cups  or  other  cause,  can  be- 
come overheated  to  such  a  degree  as  to  ignite  the  oil  in  some 
particular  spot  before  the  rise  in  temperature  would  be  indicated 
on  a  thermometer  a  few  inches  away. 

But  a  thermometer  in  a  bearing  would  indicate  from  day  to 
day,  any  difference  in  the  condition  of  either  the  lubricant  or  the 
bearing  —  for  instance,  an  engineer  on  taking  up  the  lost  motion 
of  a  main  bearing  notices  that  the  temperature  rises  10  to  20 
degrees  above  what  it  had  previously  been,  this  warns  him  that 
this  bearing  must  be  carefully  watched  to  see  that  it  does  not  get 
too  hot. 

One  of  the  essential  points  in  lubrication  is  that  the  lubricant 
be  made  to  reach  every  part  of  the  contact  surfaces,  and  in  con- 
nection with  lubrication  one  may  assume  an  oil  to  have  the  nature 
of  a  mass  of  globular  molecules  or  atoms,  which  roll  on  each 
other  and  the  wearing  surfaces  and  are  carried  or  flow  between 
the  close-fitting  surfaces  and  form  an  elastic  coating  to  the  metal, 
becoming  thinner  as  the  pressure  increases  or  the  temperature 
rises,  and  thicker  as  the  pressure  decreases,  or  the  temperature 
falls,  and  absorbing  whatever  heat  may  be  generated  and  carrying 
it  off. 

The  best  lubricant  for  a  bearing  under  normal  conditions  may 
not  do  so  well  after  heating  commences,  a  thick  viscous  oil  which 
under  ordinary  conditions  on  high  speed  machinery  would  be 
comparatively  wasteful  of  power  is  often  an  excellent  lubricant 
for  a  hot  bearing,  and  for  the  following  reason :  an  engineer  on 
finding  a  bearing  heating  up  will  apply  the  ordinary  oil  freely 


HANDBOOK    ON    ENGINEERING.  1049 

and  at  the  same  time  loosen  up  the  bolts  so  as  to  allow  for  in- 
creased expansion  and  free  flow  of  oil,  if  the  heating  continues, 
and  the  engine  or  machinery  must  be  kept  in  operation  at  all  haz- 
ards, he  will  turn  to  his  cylinder  oil,  apply  it  freely,  and  often 
with  good  results.  The  reason  of  this  is  that  the  cylinder  oil, 
owing  to  its  high  fire  test,  (from  550  to  600),  became  thin  and 
limpid  without  burning,  and  flowed  freely  between  the  close- 
fitting  surfaces  and  kept  them  apart,  and  at  the  same  time,  ab- 
sorbed the  heat  that  would  otherwise  have  gone  into  the  metal 
and  carried  it  away,  while  the  engine  oil,  being  of  lower  flash  test, 
vaporized,  and  if  the  bearing  got  hot  enough,  caught  fire. 

The  theory  of  a  heating  bearing  is  as  follows  :  If  for  any  rea- 
son the  oil  is  prevented  from  reaching  every  part  of  a  bearing, 
the  surfaces  will  come  in  direct  metallic  contact,  excessive  friction 
is  set  up  and  heat  is  generated  ;  if  the  pressure  be  not  great  and 
the  bearing  area  is  ample  the  heat  may  be  absorbed  by  the  metel 
and  radiated  out  into  the  air  and  nothing  serious  occur.  But  if 
the  pressure  is  heavy  and  the  speed  high,  the  heat  may  be  gener- 
ated faster  than  the  metal  can  carry  it  away ;  the  original  dry 
spot  may  not  have  been  over  J  or  J  of  a  square  inch  in  area  but 
sufficient  heat  may  have  been  generated  at  this  point  to  cause  the 
adjacent  oil  to  evaporate  and  shrink  away,  thus  increasing  the 
area  of  dry  surface,  as  the  heat  increases  the  metal  expands 
causing  the  surfaces  to  fit  tighter  and  thus  creating  more  friction 
until  the  temperature  reaches  such  a  point  that  it  ignites  and 
burns.  As  a  good  engine  oil  will  have  a  flash  test  of  about  400 
degrees  the  temperature  of  a  metal  must  rise  above  that  in  order 
to  ignite  the  oil. 

CYLINDER  AND  VALVE  LUBRICATION. 

In  the  lubrication  of  the  interior  wearing  surfaces  of  the  valves 
and  cylinders  of  steam  engines  conditions  will  be  met  which  are 


1050  HANDBOOK    ON    ENGINEERING. 

altogether  different  from  those  encountered  in  the  lubrication  of 
bearings  and  journals. 

In  the  latter  case,  the  working  and  comparing  of  one  oil  with 
another,  and  the  results  obtained,  can  be  easily  determined  by 
noting  the  changes  of  temperature,  etc.,  but  in  internal  lubrica- 
tion the  conditions  are  altogether  different. 

In  the  case  of  journals  and  bearings,  the  oil  can  be  applied 
directly  to  the  surface  to  be  lubricated  ;  in  cylinder  lubrication 
one  must  depend  upon  the  flow  of  steam  to  convey  the  oil  to  the 
parts  of  wearing  surfaces  requiring  lubrication. 

The  points  that  govern  the  conditions  of  interior  lubrication 
are:  The  conditions  of  the  surfaces,  the  steam  pressure,  the 
amount  of  moisture  in  the  steam,  the  piston  speed,  weight  and  fit 
of  the  moving  parts,  and  the  make  or  type  of  the  engine. 

An  automatic  cut-off  engine  with  balanced  or  piston  valves  will 
usually  require  less  oil.  than  an  engine  with  a  heavy  unbalanced 
valve. 

A  large  cylinder  whose  piston  is  supported  b}^  a  "  tail-rod  "  is 
more  easily  lubricated  than  one  whose  heavy  piston  drags  back 
and  forth  over  the  bottom  of  the  cylinder. 

The  dryness  of  the  steam  is  a  very  important  factor  in  cylinder 
lubrication,  engines  which  take  their  steam  supply  from  foaming 
or  priming  boilers,  or  through  long  uncovered  steam  pipes  usually 
require  more  oil  than  an  engine  supplied  with  dry  steam. 

Wet  steam  is  the  greatest  cause  for  complaint  in  the  lubrica- 
tion of  valves  and  cylinder  surfaces  with  which  an  engineer  has 
to  contend,  but  some  grades  of  cylinder  oil  will  give  better  results 
in  connection  with  wet  steam  than  others ;  they  will  stick  to  the 
moist  surfaces  better. 

An  engineer  who  desires  to  secure  the  best  results  and  reduce 
the  friction  loss  to  the  minimum  must  study  the  various  condi- 
tions which  exist  in  the  machinery  in  his  charge  ;  always  bearing 
in  mind  that  friction  costs  more  than  oil,  and  that  a  small  quan- 


HANDBOOK    ON    ENGINEERING.  1051 

tity  of  good  oil  properly  used  will  be  more  economical  than  any 
quantity  of  poor  oil. 

An  oil  to  be  used  as  a  cylinder  lubricant  in  order  to  give  good 
results  must  possess  certain  essential  properties. 

It  must  be  of  high  flash  test,  so  that  it  will  not  volatilize  or 
vaporize  when  in  contact  with  the  hot  steam  ;  it  must  have  good 
viscosity  or  body  when  in  contact  with  the  hot  surfaces,  and 
should  adhere  to,  and  form  a  coating  of  oil  so  as  to  prevent  wear 
and  reduce  as  much  as  possible  the  friction  of  the  moving  parts. 

Some  of  the  essentials  to  be  desired  in  a  cylinder  lubricant  are 
obtained  to  the  greatest  degree  in  the  heavier  or  more  dense  and 
viscid  of  the  petroleum  oils,  but  there  is  one  element  in  which  a 
pure  petroleum  oil  is  usually  lacking  as  a  cylinder  lubricant  and 
that  is  its  inability  to  adhere  to  a  wet  surface,  and  for  that  reason 
it  is  necessary  that  it  be  combined  with  some  one  or  more  of  the 
various  vegetable  or  animal  oils. 

There  is  always  a  certain  amount  of  moisture  present  in  the 
valve  chambers  and  cylinders  of  a  steam  engine,  due  partly  to 
condensation  of  the  steam  in  the  pipe  on  its  way  from  the  boilers 
to  the  engine  and  partly  to  the  expansion  which  takes  place  in  the 
cylinders. 

A  petroleum  oil,  while  it  may  possess  the  proper  viscosity  and 
flash  test,  will  not  of  -itself  mix  with  or  form  an  emulsion  with 
water  and  consequently  will  not  stick  to  the  moist  surfaces,  but 
will  be  easily  washed  out  by  the  action  of  the  steam  ;  but  animal 
and  vegetable  oils,  while  not  so  viscid 'as  the  petroleum  oil,  will 
combine  with  it  and  emulsify  freely  with  water  and  when  com- 
pounded in  the  proper  proportions  with  a  heavy  petroleum  pro- 
duce a  cylinder  oil  that  is  suitable  for  interior  lubrication. 

While  the  quality  of  a  cylinder  oil  as  shown  by  the  use  of 
testing  instruments  will  give  one  a  general  idea  of  its  lubricating 
value,  the  engineer  who  is  studying  the  question  cf  cylinder  lub- 
rication can  determine  more  accurately  its  exact  value  by  experi- 


1052  HANDBOOK    ON    ENGINEERING. 

meriting  on  his  engines  and  pumps  and  under  the  conditions 
peculiar  to  his  own  plant. 

Any  engineer  in  charge  of  a  steam  plant  knows  that  nearly 
every  engine  will  indicate  either  audibly  or  otherwise  perceptibly, 
any  lack  of  lubrication. 

A  Corliss  type  of  engine  will  usually  indicate  need  of  more 
cylinder  oil  by  a  slight  groaning  of  the  valves,  if  not  loud  enough 
to  be  heard,  it  can  be  detected  by  feeling  of  the  valve  stem,  or  by 
the  vibration  or  trembling  of  the  valve  and  eccentric  rods. 

Buckeye,  Russell,  Porter- Allen  and  other  makes  of  engines 
with  balanced  valves  will  usually  indicate  a  lack  of  oil  by  a  rattling 
noise  in  the  steam  chest,  rocker-arms  and  the  eccentric  and 
governor  connections. 

For  instance,  an  engineer  has  submitted  to  him  for  trial  three 
sample  lots  of  cylinder  oil,  and  he  wishes  to  determine  which  is 
the  most  suitable  and  economical  oil  for  him  to  use ;  he  may 
notice  after  starting  with  the  first  sample  that  the  valves  work 
free  and  smooth  on  say,  eight  (8)  drops  a  minute;  he  then  re- 
duces the  oil  feed  gradually  to  four  (4)  drops,  and  then  notices 
a  slight  tremor  in  the  eccentric  rods,  and  later,  if  a  Corliss  engine, 
he  may  detect  a  decided  groaning  sound  in  one  or  more  of  the 
valves. 

If  the  oil  feed  is  then  increased  to  six  (6)  or  seven  (7)  drops 
per  minute  and  the  valves  begin  to  work  freely  again  and  when 
the  oil  feed  is  reduced  to  five  (5)  drops  and  the  valves  commence 
to  work  hard  again,  and  'the  results  are  the  same  after  repeated 
trials,  the  engineer  can  determine  just  how  much  of  this  particu- 
lar brand  of  oil  is  required  to  keep  the  valves  working  smoothly 
and  quietly. 

The  next  thing  in  order  is  to  remove  the  cylinder  head  or  steam 
chest  cover,  or  if  a  Corliss  engine,  draw  out  one  of  the  valves  and 
examine  the  wearing  surfaces ;  if  well  lubricated  they  will  present 


HANDBOOK    ON    ENGINEERING.  1053 

a  dark  glossy  appearance,  and  a  good  coating  of  oil  all  over  the 
interior  surfaces. 

The  most  reliable  test  of  the  condition  of  the  surfaces  is  to 
wipe  over  them  with  a  piece  of  soft  white  paper,  such  as  a  piece 
of  ordinary  newspaper ;  if  a  decided  stain  of  oil  is  seen  on  the 
paper  it  is  an  indication  of  good  lubrication.  Another  method  is 
to  wipe  over  the  surface  with  several  thicknesses  of  tissue  paper 
and  note  the  number  of  thicknesses  that  the  oil  has  saturated 
through. 

But  if  no  stain  of  oil  can  be  seen  upon  the  paper  and  the  sur- 
faces have  a  dull  appearance,  and  with  traces  of  metallic  wear  it 
is  a  positive  evidence  that  the  oil  is  not  lubricating  properly. 

Then,  if  another  sample  of  oil  is  tried  and  it  is  found  to  require 
from  ten  (10)  to  twelve  (12)  drops  per  minute  to  keep  the  valves 
quiet,  and  the  surfaces  when  examined  showed  little  or  no  signs 
of  oil,  it  would  prove  conclusively  that  it  is  a  very  poor  lub- 
ricant, and  would  be  a  most  expensive  oil  no  matter  how  cheap 
in  price  per  gallon. 

But,  if  after  trying  the  third  sample  it  will  be  found  that  the 
oil  feed  can  be  reduced  to  one  (1),  two  (2),  or  three  (3)  drops 
per  minute,  or,  perhaps  one  (1)  drop  every  two  minutes,  and 
kept  at  that  rate  for  hours,  without  showing  any  evidence  of  lack 
of  perfect  lubrication,  and  the  surfaces  after  standing  cold  for 
several  hours  still  show  a  good  coating  of  oil  and  no  rust  or 
"  raw  spots,"  and  these  results  hold  good  on  all  the  engines  and 
pumps  in  the  plant,  it  would  prove  conclusively  that  this  oil  will 
be  the  cheapest  to  use  no  matter  what  the  price  per  gallon  may  be 
and  regardless  of  all  laboratory  tests. 

LUBRICATION  OF  REFRIGERATING  MACHINERY. 

In  the  operation  of  refrigerating  machinery  certain  conditions 
exist  which  require  that  the  oil  used  for  lubrication  shall  be  of 


1054  HANDBOOK    ON    ENGINEERING. 

such  a  nature  that  it  can  be  subjected  to  quite  a  high  temperature 
and  to  a  very  low  temperature  without  congealing. 

In  the  manufacture  of  artificial  ice,  or  to  speak  more  correctly, 
in  mechanical  refrigeration,  the  anhydrous  ammonia  gas  is  com- 
pressed in  the  compression  cylinders  to  about  120  to  200  pounds 
pressure  per  square  inch,  according  to  the  class  of  work  done, 
and  the  requirements  of  the  plant.  It  is  then  allowed  to  expand 
down  to  about  15  pounds  in  the  expansion  coils.  In  some  types 
of  machines  oil  is  used  to  lubricate  the  ammonia  cylinders  and 
pistons  and  to  fill  the  clearance  space  and  to  reduce  the  heat  of 
compression,  for  in  compressing  the  ammonia  gas  to  the  required 
pressure  its  temperature  is  raised  to  about  180  to  200  degrees. 
And  the  oil  for  this  purpose  must  have  a  flash  point  so  high  as  to 
not  give  off  any  great  amount  of  vapor. 

After  the  ammonia  has  been  compressed  to  the  proper  extent 
it  is  allowed  to  flow  through  the  expansion  coils  and  thus  pro- 
duce the  refrigerative  effect. 

All  refrigerating  plants  are  provided  with  a  separator  in  the 
ammonia  discharge  pipe  which  is  supposed  to,  and  does  to  a  cer- 
tain extent,  separate  the  oil  and  other  foreign  matter  from  the 
ammonia ;  but  a  certain  quantity  of  oil  will  always  go  past  the 
separator  in  the  form  of  vapor  and  collect  in  the  condensing  coils, 
so  that  it  is  very  essential  that  the  oil  be  of  such  a  nature  that  it 
will  remain  in  a  fluid  state  when  subjected  to  low  temperatures. 
If  the  oil  be  of  poor  cold  test  it  will  congeal  and  form  a  coating 
on  the  inside  of  the  coils  and  tend  to  lower  the  efficiency  of  the 
system  and  eventually  clog  up  the  pipes. 

An  oil  for  this  work  should  be  of  30  gravity,  of  about  300  to 
325  flash  test,  and  stand  a  temperature  of  5  degrees  above  zero 
without  congealing. 

Different  makes  of  refrigerating  machines  have  different  re- 
quirements as  to  the  use  of  oil.  The  De  La  Vergne  machine  is 
what  is  known  as  the  double-acting  type,  and  oil  is  used  to  fill 


HANDBOOK    ON    ENGINEERING.  1055 

the  clearance  space  as  well  as  to  lubricate  the  cylinders  and  pis- 
tons. On  some  makes  of  machines  the  oil  is  only  used  in  the 
space  in  the  stuffing  boxes  on  the  piston  rods,  and  none  is  fed 
into  the  compression  cylinders ;  but  no  matter  how  tight  the 
packing  is  kept  some  of  the  oil  will  work  through  into  the  cylin^ 
ders  and  pass  out  with  the  ammonia  gas ;  and  notwithstanding 
the  fact  that  the  discharge  pipes  are  provided  with  separators, 
some  of  the  oil  will  pass  through  into  the  system. 

In  the  lubrication  of  the  steam  cylinders  of  a  refrigerating 
plant,  especially  where  ice  is  made,  certain  points  must  be 
looked  after  that  are  not  essential  in  any  other  class  of  engine. 

It  is  customary  in  the  manufacture  of  ice  to  condense  the  ex- 
haust steam  and  purify  it,  and  use  it  to  make  ice  of ;  and  for  this 
reason  the  oil  used  for  lubricating  the  valves  and  surfaces  of  the 
steam  cylinders  should  be  of  pure  petroleum  or  very  nearly  so ; 
and  it  is  well  for  the  engineer  in  charge  of  a.  refrigerating  plant 
to  go  on  the  theory  that  the  less  oil  used  in  the  cylinders  the  less 
there  will  be  to  separate  from  the  condensed  water.  The  steam 
cylinders  of  refrigerating  machines  are  not  as  a  rule  very  large, 
and  the  piston  speed  does  not  as  a  rule  exceed  400  to  600  feet 
per  minute,  so  that  if  a  first  class  quality  of  oil  is  used  very  little 
will  be  required  to  give  good  lubrication. 

In  the  process  of  making  ice  the  exhaust  steam  first  passes 
through  a  separator  where  the  steam  is  relieved  of  some  of  the 
oil ;  from  there  it  passes  to  a  feed  water  heater,  where  it  im- 
parts some  of  its  heat  to  the  boiler  feed  water,  then  it  goes  to  the 
condenser  and  is  condensed  and  the  water  of  condensation  is 
pumped  to  a  re-boiler  and  skimmer  ;  and  any  oil  that  has  not  been 
removed  in  the  preceding  processes  is  taken  off,  the  water  passes 
through  the  cooling  coils  and  on  to  the  bone  dust  or  charcoal 
filters,  where  it  is  still  further  cleaned  of  its  impurities,  from 
there  it  passes  to  the  settling  or  sweet  water  tank,  as  it  is 


1056  HANDBOOK    ON    ENGINEERING, 

called,  and  it  is  finally  drawn  off  through  a  sponge  filter  on  its 
way  to  the  freezing  cans. 

From  this  it  will  be  seen  how  important  it  is  that  the  water 
be  kept  as  free  from  oil  as  possible.  If  the  oil  contains  any 
great  amount  of  animal  fats  in  its  composition  it  will  form  a  white 
milky  looking  emulsion  with  the  water  that  will  be  very  difficult 
to  remove. 

The  presence  of  a  yellow  or  reddish  color  in  the  ice  is  often 
attributed  to  the  cylinder  oil  getting  in  the  ice.  This  may  some- 
times happen  when  the  oil  is  used  too  freely,  or  the  filters  are  out 
of  order ;  but  as  a  general  thing  the  stain  is  due  to  the  presence 
of  rust  in  the  water.  Condensed  water  has  a  very  active  effect 
on  iron  when  combined  with  oxygen,  and  when  the  plant  is  shut 
down  and  the  pipes  are  empty  the  action  of  the  air  on  the  moist 
pipes  soon  causes  them  to  rust,  and  when  the  plant  is  started 
again,  unless  care  is  taken  to  prevent  it,  the  rust  will  be  de- 
posited in  the  freezing  cans. 


INDEX. 


AIR,  composition  of,  651. 
f(    compressor,    Bennett,      auto- 
matic, 803. 

"     compressor,  capacity  of,  800. 
"    compressor,  effect  of  fly  wheel, 

806. 

"    compressor,  horizontal,  802. 
"    compressor,      Ingersoll  -  Sar- 
gent, 804. 
"    compressor,  McKierman  Drill 

Co.'s,  801. 

"    lift,  construction  of,  808. 
"       "     formulas,  808. 
"      "    required  for  combustion, 

484. 

"    volume  per  pound  of  coal,  651. 
Arc  lighting  apparatus,  103. 
Atmosphere,  pressure  of,  560. 
Atmospheres,  number  of,  to  find, 

806. 

Atmospheric  pressure,  233,  661. 
Auxiliary  injection,  259. 
BANKING  fires,  531. 
Belts,  adjusting,  798. 

arc  of  contact,  795,  799. 
driving  power  of,  788. 
effect  of  size  of  pulley,  791. 
effect  of  speed,  793. 
grain  side  of,  768. 
horizontal,  797. 
horsepower  of,  789,  793,  799. 
inclined,  797.  % 
lacing,  798. 
laws  relating  to,  791. 
length  required,  789. 
long,  effect  of,  787. 
making  joints,  799. 
proper  direction  to  run,  798. 
pull  on,  795. 

punching  for  lacing,  798. 
resistance  to  slippage,  792. 
short,  effect  of,  797. 


Belts,  slippage,  cause  of,  791. 
"      speed  of,  793. 
"      testing    adhesive    qualities, 

792. 

<e      to  increase  power  of,  798. 
"      width  of,  789,  797. 
Bevel  wheels,  707. 
Biowoff  cocks,  435. 
Boiler,  area  of  head  to  be  stayed, 

938. 
"     blowing  out,  frequency  of, 

435. 

"      calking  leaks,  535. 
"      capacity,  to  heat  water  in 

tank,  479. 
"      capacity  to  heat  swimming 

pool,  479. 

"      care  and  management,  433. 
"      cause  affecting  strength,  450. 
"      cleaning,  533. 
"      compound,  how  to  use,  655. 
"      cooling    down    and  filling, 

534. 

(l      definitions  applied  to,  415. 
"      efficiency,   on    what  it  de- 
pends, 664. 

"      foaming  and  priming,  535. 
"      furnaces,  432. 
"      hammer  test  for,  447. 
"      heating  surface   in    square 

feet,  501. 
"      heating    surface    required, 

327. 

"     height  of  fire  line,  669. 
u      horsepower,    A.  S.   M.   E. 

rating,  406. 

"      horsepower  of,  663. 
"      horizontal,  how  to  set,  671. 
"  "  specifications, 

for,  524-527. 

(f      importance  of    circulation, 
421,  423. 

(1057) 


1058 


INDEX. 


Boiler,  inspection  of,  328. 

"      instruction    for    attendant, 

532. 

laying  up,  649. 
leaving  at  night,  650. 
low  water,  what  to  do,  325. 
materials,    definitions,     ap- 
plied to,  415. 
operating  valves  on,  535. 
plain  vertical  tubular,  514. 
plate,  characteristics  of,  662. 
t(     manufacture    and  use 

of,  460. 
"        "      strength  between  rivet 

holes,  537. 
"        "        strength     of     solid, 

537. 
"      proper  point  for  closing  in, 

520. 

"       raising  steam  in,  324. 
(e      rating    by  weight   of   feed 

water,  676. 
"      reinforcing    ring,    size    of, 

541. 

"      selection  of,  422. 
"      stayed    surfaces,    strength 

of,  473. 

"      starting  and  stopping,  532. 
"      staying  heads,  938. 
ie      stays,  474. 
"      the  Heine  safety,  507. 
"      the  O'Brien,  503. 
"      to  manage  with  low  water, 

649. 

"      trimmings   426. 
"      water  tube,  sectional,  502. 
Boilers,  blister,  cause  of,  444. 

t(      cheap,  not  economical,  453. 
"      common  types  of,  402. 
<f      corrosion  in,  445. 
"      defects     in     construction, 
"         457. 
"       design  of,  454. 
u      deterioration,  cause  of,  451, 
(f      energy  stored   in,  400,  448. 
"      firebox,        when       recom- 
mended, 425. 
"       forms  of,  456. 
"      hard  patch  for,  444. 


Boilers,  heating    surface  required, 
403. 

(e      horsepower  of,  402. 

"  what  it  is,  405. 

"       improvements  in,  459. 

te       inspection  of,  445. 

i(      material  required    for  set- 
ting, 522. 

"      method  of  comparing,  403. 

"       patching,  444. 

"       preventing  corrosion,    443. 
"  leaks,  443. 

u       proportions  of  joints,  467- 
472,  946. 

f<       pulsation  in,  487. 

"      rating  of,  404. 

'•       riveted  seams,  strength  of; 
461. 

"      rules  relating  to,  536. 

t(      safe  working  pressure,  516- 
519. 

"       settings  for,  456. 

"      single   and  double  riveted 
seams,  462. 

"       soft  patch,  444. 

"      special  high  pressure,  401. 

"       stayed  and    flat    surfaces, 
473. 

"      steel  for  use  in,  425. 

"      strength  of,  on  what  it  de- 
pends, 455. 

"       submerged  tubes,  521. 

"       testing  of,  447. 

te      tests,  rules  for  conducting, 
407. 

"      tubular,       when       recom- 
mened,  425. 

fc       use  and  abuse  of,  449» 

et       use  of  zinc,  442. 

"        vertical,      when      recom- 
mended, 425. 

et        working     beyond       rated 
capacity,  451. 

"        working  capacity   of,  405. 
British  thermal  unit,  what  it  is,  401. 
"  "          "      mech.  equiva- 

lent, 688. 

CARBONATE  of  lime,  440. 
Centigrade  thermometer,  811. 


INDEX. 


1059 


Centrifugal  force,  501. 

Changing  from  non-condensing  tc 

condensing  238. 
Chimney,  688. 

"  cause  of  draft,  670. 

"  horsepower  of,  692. 

te  stacks,  692. 

Cisterns,  capacity  of,  585. 
Cleaning  tubes,  436. 
Clearance,  definition  of,  653,  659. 
Coal,  composition  of,  651. 
"     horsepower  for  1  pound,  420. 
"     required    to   heat    water    by 

steam,  479. 

"     value  of,  per  pound,  404. 
Combustion,  air  required  for,  419. 
Compound  engine,  253. 
Compressing,  adjusting  valves  for, 

212. 
Condenser,  235. 

"  auxiliary  injection,  259. 

t(  device     for     breaking 

vacuum,  247. 
"  distance      will       raise 

water,  249,  250. 
"  gain  by  using,  654. 

"  jet,  246. 

"  jet,  method  of  connect- 

ing, 248. 

safety  device  for,  248. 
siphon,  249. 
"        and       starting 

valve,  251. 

t(  cc        method,  of  con- 

necting, 252. 
"  speed  of,  254. 

starting  the,  258. 
surface,  243. 
"  "       efficiency    of, 

661. 

type^  of,  242. 
"  water      required     for, 

237,  258,  670. 

Condensing  to  noncondensing,  238. 
Connecting  rod  brasses,  189. 

1  "    effect   on      cutoff, 

671. 

"  •  "     to  find    length  of, 

667. 


te 
if 


tc 

u 


Copper  staybolt,  grip  of,  474. 
Corliss  engine,    double   eccentric, 

215. 
"  "  long  range  cutoff, 

215. 

"  "  steam      distribu- 

tion, 219. 

"  "  governor,  adjust- 

ing, 214. 
Crankpins,  188. 
Cutoff,  equilizing,  213,  267. 
Cylinder,  capacity  in  cu.  ft.,  801. 

"  lubrication,  309. 
Dead  center,  to  find,  195. 
Decimal  equivalents  of  an  inch, 

1024. 
Double  eccentric  valve  gear,  215- 

222. 

Do  you  do  these  things,  388. 
Draft,  effect  of  bad,   on  economy, 

327. 

Dynamos  and  motors,  care  of,  80. 
EBULLITION,  439. 
Eccentric  diagrams,  361. 

"        effect  of  shifting,  361. 
"  "     of  moving,  319. 

out  of  place,  360. 
rod,  length  of,  668. 
"        "        with         link 
motion,  317. 
straps,  192. 
throw,  390. 

Electrical: — 

Alternating  and  direct  currents,  18. 

A.C.  E.M.F.,  821. 

"    generators,  armature  circuits, 

106. 

belted,  888. 
Brush  arc,  104. 
care  of,  890. 
commutators,    866. 
compensating     and 
compounding,|864. 
generators,  compound,  887. 
a  compounding,  85?. 

"          connecting  to 

switchboard,  862. 
"         direct  coupled,  888. 


1060 


INDEX. 


(C 

u 


Electrical : — • 

A.  C.  generators,  division  of    load, 

887. 

u         exciter,  use  of,  864. 
"          how  run,  859. 
"         inductor,    type  of, 

857. 

<»         operation,  110. 
t(  "          regular  speed  for, 

861. 

•«  '  regulator,  108. 

"  "          revolving  field,  857. 

€i  u         running  in  parallel, 

861,  887. 
"  lt         setting        brushes, 

110. 

"  "          shutting  down,  890. 

"  "          starting  a,  889. 

"  "          two      and      three- 

phase,  854. 

"  "         voltage  of,  106. 

Ammeter  and  voltmeter,  construc- 
tion of,  60. 

Ammeter  where  placed,  50. 
Ampere,  turns  required,  46. 

"        what  it  is,  73. 
Angle  of  lag,  837. 
Arc  lamp,  enclosed,  A.C.,  103. 
r<       "      constant  current  circuits, 

127. 
"      "       Fort      Wayne     systems, 

126,  150. 

"      "      series  system,  112,  118. 
"      "      series    system,    regulat- 
ors, 120,  124. 

"      ft      series    system,     switch- 
boards, 114,  117,  118. 
"      "        series     systems    trans- 
formers, 113,  120. 
"      "        carbons,  156. 
'•       (*        carbons,   diam.,  length 

and  quality,  157. 
ft      "        carbons,  for  D.C.    and 

A.C.,  136. 

"      "        frequency  of,  159. 
"       "        life  of,  157. 
"      "        polarity  of,  158. 
Arc  lamps,  128,  132,  147,  159. 
"      (t        carbon  holders,  135. 


Electrical: — 

Arc  lamps,  care  of  gas  check,  158. 
"       "         clutches,  133,  158. 
"      (-        condition  of  globes,  159. 
"       •'        connection     to     upper 

carbon.  135. 

"       "        constant  potential,  146e 
"      "        current     consumption, 

154,  156. 

"       "        cut  out  for,  145. 
"       "         dashpot,  158. 
"      "        direct  current,  136,  145. 
f<      "        directions  for  care,  156. 
"       t(        enclosed,  103,  151,  156, 

159. 

"       <e        Excello,  153,  155. 
u      "        flaming    arc  type,    152, 

156. 

"       "        for  power  circuits,  141. 
"       "         Fort  Wayne,    131,   134, 

135,  139,142,147,151. 
"       "        frequency    of  alternat- 
ing, 159. 

"      "        General    Electric,    128, 

136,  137,    144,     149, 
155,  156. 

"       "        how  to  install,  159. 
"      "        how  to  trim,  157. 
"       "        inner  globes,  158. 
"      "        inspecting     mechanism 

159. 

"      "        life  of  carbons,  155. 
"       "        multiple  series,  141. 
"       "        use  of  oil,  159. 
a      "        Western   Electric,    132, 

134,  135. 
"       "         Westinghouse,  129, 134, 

139,  144,  148. 
Arc  lighting,  A.C..,  104. 

s(          apparatus,  103. 
"  "          constant       current 

circuits,  127. 
<f  "          constant  potential, 

136,  146. 

"  "          direct  current,  136. 

"  "          Fort  Wayne  street, 

150. 

te  tc          power  circuits,  141. 

te  <e          series  system,  112. 


INDEX. 


1061 


Electrical: — 

Arc  lighting,  coils,  connections  of. 

30. 
Armature,  cores,    construction  of, 

23. 

effect  of  displacement^, 
flow  of  current  in,  84. 
method  of  raising,  75. 
principle  of,  16. 
pull  of,  63. 
ring,  27. 

Balance,  effect  of  distributing,  96. 
Batteries,  81. 

Brushes,  connection  to,  40. 
"        number  of,  39. 
«        position  of,  36,  85. 
Candle  power,  measurement  of,  73, 
Circuit  breakers,  principle  of,  62. 
Collector  rings,  arrangement  of,17. 
Commutator,  care  of,  76,  88. 

lf  construction  of,  18. 

Condenser,  use  of,  840. 
Conductors    and    non-conductors, 

14. 

Constant  current  machines,  34. 
Construction  of   bipolar  machine, 

22. 
Current,  how  generated,  12. 

"        measure   of  strength,  73. 
Cylinder  controller,  72. 
Direction  of  rotation,  effect  of,  15. 
Distributing  boards,  59. 
circuits,  47. 

Distributions,  A.  C.  882. 
Drum  and  barrel  windings,  45. 

"      armature,  29. 
Dynamos,   switching  into    circuit, 

78. 

Effect  of  current  on  needle,  8. 
"     u    direction    of    current  on 

conductor,  11,  19. 
"     "    number      of       armature 

coils,  25. 

"    "    number  of  poles,  39. 
"     "    turns  of  wire,  20. 
Electro-magnetic  induction,  14. 
Electromotive    force,    how    deter- 
mined, 15. 
Elevators,  716,  769. 


Electrical: — 

Elevators,  belt  driven,  717. 

"          cable-drive     machine, 

781. 

car  switch,  748. 
"          controller  for,  728,  775, 

777,  785. 
"          diagram  of  wiring,  774. 

784. 
"          diagrams     of     traction 

types,  779. 
direct,  driven,  730. 
duplex  motor,  772. 
Frazer  duplex,  770. 
"          limit  of  drum  type,  769. 
"          limit  switch,  776. 
'•          machines,  care  of,  739- 

765. 
•'          machines,    Otis  .direct 

connected,  741. 

"        machines,  types  of,  756. 
if          method  of  controlling, 

773. 

motor,  care  of,  726. 
"  plants,  installation    of, 

726. 

"          traction  type,  778. 
Equalizing  connections  from  gen- 
erator, 63. 
Field  coils  of  multipolar  machines, 

45. 

Fluctuation  of  current,  24. 
Form  of  curve,  823. 
Formulas,  891. 
Fuses,  location  of,  60. 
Generator  and  motor,  installing,  74. 
"          "        "     running  in  par- 
allel, 79,  80. 

"         Brush  arc,  103-110. 
"         compound,  connections, 

53. 

"  "          operation,  34. 

"  "          wound,  start 

ing,  55. 

"         constant  potential,  34. 
"         heating  in,  93. 
"          multipolar,  38, 
"          noise  in,  91. 
"         principle  of,  7. 


1062 


INDEX. 


Electrical:— 

Generator,  series  and  shunt,  81. 

"          starting  a,  77. 
Impedance,  diagram,  837. 
Impressed,  E.  M.  F.,  838. 
Inductive  action,  834. 
Instruments  required  in  circuit,  49. 
Lap  winding,  42. 

Light  and  power  systems  for  build- 
ing, 58. 

Lightning  arrester,  loca  ion,  49. 
Lines  of  force  around  conductors,  9. 

«     «      «      direction  of,  5. 
Live  and  dead  side  of  coil,  29. 
Long  shunt,  32. 
Magnetic  field,  10. 

tf        flux  through  armature,  63. 
"        force,  how  measured,  13. 
Magnetization  of  field,  32. 
Magnet,  lifting  capacity  of,  13. 

tl        needle,  3. 
Motor,  compound,  35. 

"      current  required  by,  57. 

"     effect  of  overloading,  65. 

4<     field,  regulating  strength,69. 

11      heating  in,  93. 

"     induction,  871. 

"     induction,  three-phase,  877. 

"      principle  of,  11. 

"     principle     of    synchronous, 
867. 

t(      reversing  the    direction  of, 
70. 

"       shunt  and  compound,  33. 

•'       shunt,  varying  speed  of,  71. 

<e      single    phase  synchronous, 
70. 

"       starting  switch,  65. 

"       to  start,  68. 

te      two  and  three-phase,  70. 

"      variable  speed,  68. 
Motors,  64. 
Mutual  induction,  842. 
Ohm,  definition,  73. 
Panel  boards,  59. 
Permanent  magnet,  1. 
Personal  safety,  129. 
Phase,  meaning  of,  828. 
Polyphase,  832. 


Electrical: — 
Power  factor,  870. 
Principles  of  A.  C.,  870. 
Reactance,  830. 
Resistance  of  conductor,  15. 
"        regulator,  48. 
"        to  magnetic  force,  21. 
Rotary  converter,  886. 
Rotary  converter  for  St.  Ry.,  885. 
"        transformers   and  convert- 
ers, 878. 
"        transformers  connection  of 

brushes,  881. 
Self-induction,  829. 
Sine  curve,  824. 

"      "        diagram,  831. 
Soldering  fluid,  101. 
Strength  of  current,  how  measured, 

15. 
"        "  field,   effect  on  speed, 

12. 
Switchboard  for  three- wire  system, 

57. 

"  for  two  generators,  51. 

<e  general   arrangement, 

50. 

Switchboards  and  instruments,  47. 
Synchronizer  or    phase   indicator, 

862. 

Synchronizing  lamps,  861. 
Transformers,  kinds  of,  850. 

fC  principle  of,  844. 

fe  use  of,  849. 

Two  and  three-phase  systems,  883 
Two  and  three-wire  systems,  56. 
Two-bar  magnets,  3. 
Voltage,  effect  on  number  of  lamps, 

56. 

Watt,  what  it  is,  73. 
Wave  winding,  43. 
Winding  for  four-pole  machine,  39. 
"        "    multipolar  armatures, 

40. 

Why  commutators  spark,  82. 
Elevator  safeties,  1025. 

"  <f         brake  or  clamp,, 

type, 1031-1034. 
4i  ee       cable  connections, 

1031. 


INDEX. 


1063 


Elevator  safeties,  miscellaneous  de- 
vices, 1037. 
f<  ee        proper    care    of, 

1037. 
(C  ft        requirements   of, 

1027. 
"  •'        roller  type,  1028- 

1030. 
"  "        speed    governors 

for,  1027. 

"  {f        type     used    with 

electric      eleva- 
tors, 1035-1037. 
"  "        wedge  type,  1025. 

"  "         wedge  type,  mod- 

ification of,  1027. 
tf  "        wedge  type,  Otis, 

1025. 

Engine,  Armlngton  and  Sims,  290. 
u        automatic,  376. 
"        care  and  management,  185. 
"        compound,  222. 
"  "  adjusting  gov- 

ernor, 232, 
te  <c         equalizing  load, 

230. 

"  "         horsepower,  232. 

"  "        mean      effective 

pressure,  232. 

"  "        points  of  cutoff, 

231. 
•f  u        proportion    of 

cylinders,  227. 

"  te          reheater,  255. 

"  "         starting,  257. 

"  "         starting         and 

running,  253. 

"  "         total  no.  of  ex- 

pansions, 228. 

<l  "         types  of,  224. 

"       condensing,  232. 
"  "  advantage    of, 

234. 
"       connecting  piston  rod  and 

crosshead,  190. 
"       Corliss,      adjustment       of 

valves,  206. 

41      Corliss,    double  eccentric, 
669. 


Engine,  effect  of  cut  off  and  speed, 

380. 

"  formulas,  203. 
<e  foundation,  182. 
f<  high  speed,  179. 
"  horsepower,  649. 
"  how  to  line,  199. 
"  Ideal,  298. 

"      length  of  stroke,  to  find,  273 
"      location  of,  181. 
"      low  speed,    advantage    of. 

179. 
<s      performance    of    non-con- 

densing,  183. 
**  repairs  for,  191. 
u  running  ^over'  and 

<  under,'  668. 

"       selecting  oil  for,  187. 
"       selection  of,  177. 
"      sett  ug  up  and  running  Cor- 
liss, 205. 

"      the  most  economical,  182. 
"       throttling,  376,  379. 
"      to  increase  horsepower  of, 

383,  385. 

te      to  increase  speed  of   381. 
"      to    line   with  direct  shaft- 
ing, 387. 
"      to  line   with  line  shafting, 

385. 

"      triple  expansion,  653. 
Engines,  automatic,  194. 

^  «  cutoff,  339. 

"        clearance  spaces,  276. 

"        gene  al  proportions,  275. 

"         regular  expansion,  338. 

"        slide  valve,  337. 

"        steam  used  by,  403. 

•c        water  required  by  small, 

676. 

"      weights  of,  273 
"  f<        per     rated    horse- 

power, 276. 
Engineer,   the    first  duty   of,   323, 

325,  656. 
Evaporation,  factor  of,  539. 

"  highest  average,  327. 

Exhaust  pipes,  275. 
Expansion  curve,  locating  true,  354. 


1064 


INDEX. 


Expansion  gain  by,  183,  336. 

"        to  find  number,  226. 
FAHRENHEIT  thermometer,  809. 
Fairburn's  experiments,  473. 
Feed  water,  gain  by  heating,  680. 
"  heater  open,  681. 

"  heaters,  678. 

Firebrick,  433. 
Fly-wheel,  184. 

weights  of,  276. 
"          why  used,  655. 
Foaming  and  priming,  436. 
Friction  and  lubrication,  1040. 
u      coefficient  of,  1042. 
"      laws  of,  1040. 
"      uses  of,  1041. 
Fuel,  utilization  of,  327. 
Furnace  boiler,  431,  513,  525. 
"       down  draft,  522. 
"      grates,  how  set,  670. 
Fusible  plug,  533. 

"       plugs,  care  of,  435. 
GEARING,  construction  of,  706. 
Governor,  183. 

"          adjustment    for    riding 

cutoff,  268. 

"          the  Gardner,  341. 
"          throttling,  666. 

to  block  up,  669. 
Gauge  cocks,    location  and    care, 

429,  434,  521. 

"      glass,    location    and     care, 

434. 
"      steam,  connections  and  care 

430,  434,  489. 

HARRIS  BURG  engine,  291. 
Heat  and  steam,  416. 

"     in  water  between  32°  and  212°, 
604. 

"    latent,  583,  652. 

"     measurement  of,  419. 

"    mechanical  equivalent,  420. 

(e    of  combustion,  418,  484. 

"    radiation  of,  421. 

"     sensible,  definition,  657. 

"     utilization  in  boiler,  417. 
Heater,  capacity  for  heating  water, 

482. 
Heating  surface,  definition,  663. 


Heating  surface,  per    horsepower 

648. 
Horsepower,  185,  275. 

"  definition  of,  653. 

indicated,  353. 
<e  of  gears,  695. 

"  of  shafting,  697. 

Hydraulic  elevators,  954. 
Hyd.  Elev.  accumulators,  996. 
"        "  "  construc- 

tion of, 
996. 

"        te  "  operation 

of,  997. 

"        "        cables,  care  of,  1021. 
"        "  "       lubrication, 

1023. 

"        "        car,    settling  of,  1019. 
"        "        circulatingpipe,  967. 
"        "        closing  down,  1022. 
se        "        controllers,         circuit 

connections,  986. 
"        "        controllers,       eleotric 

floor,  985. 
<e        "        controllers,  operation, 

986. 

"        "        Crane,  959. 
"        "        cylinder   and  plunger, 

1005. 
"        "        double  power  type, 

987. 

u        enclosures,  1019. 
"        gear  of,  956. 

"     operating,  956. 
"        "        guides,       lubrication, 

1023. 
(t        "        hand   rope    operation, 

967. 
"        "        high     pressure     type, 

988. 

"        "        horizontal,  954. 
"        "  "  high  pres- 

sure, 990. 
"        "        leaks,     how    to    find, 

1023. 

"        "        lubrication,  102.3. 
tf        u         Morse     and    Williams 

design,  961. 
"        "        Otis  vertical,  966. 


" 


INDEX. 


1065 


Hyd.   Elev.  piston,    packing    Otis 

vertical,  1014. 
"        fe        piston,  rods,  packing, 

Otis,  1016. 
"        "        plunger,  balancing  of, 

1001. 
"         "  "          construction, 

1000. 

"         "  "         Plunger    Elev. 

Co.'s,  1001. 

"        "  "         Standard  Plun- 

ger Elev. 
Co.'s,  1001. 
«        type,  998. 
tf        u        pulling  machines, 

horiz.,  963. 
"        'f        pushing  machines, 

horiz.,  956. 

"        se        ropes,  standard,  hoist- 
ing, 1021. 
"        "        sheaves,      lubrication, 

1023. 
"        "        sheaves,  traveling, 

1007. 
"        "        stop    balls    for     hand 

rope,  1019. 

"         "         types  of,  954. 
"        "        valve  construction, 

971. 
"        "  "     hand   rope   type, 

1013. 

"         "  "     Otis,   main,   976. 

"         <l  "     pilot,  976,  1005. 

"        "  "        "      battery 


type.  981.      1 

ndic* 

control,           I 

ndic* 

971. 

floor  con- 

< 

troller, 

( 

push  but- 

( 

ton,   985. 

t 

for  verti- 

cal,   990. 

i 

magnet 

t 

control, 

979. 

it 

push  but- 

ton con- 

a 

trol,  983. 

Hyd.  Elev.   valve   running    and 
standing  rope, 
957. 
"        "  "     speed  governing, 

994. 
"        "  "     Standard  Plunger 

Co.'s,  1007. 

'•'       "  a     stop  for  accumu- 

lators, 997. 
"        "        valves,  action  of  limit, 

1007. 
"        "  (t        automatic  stop, 

973-1003. 

"        "  t(       cup  packing 

for,  1022. 
"        "  "        for  double 

power,  988. 

"        "  "        limit,  1012. 

"        "  "       main  and  pilot, 

959,  975,  978, 
1008,   1010. 

"        "  "       plunger  type, 

limit  stop, 
1003. 
"        "        vertical  high  pressure, 

990. 

"        "  "        type,  966. 

"        "        water  for,  1017. 
a        K        Whittier  design,  963. 
Hyperbolic  curve,  to  draw,  355. 
IGNITION  point  of  various   sub- 
stances, 589. 

Inches  in  decimals  of  a  foot,  714. 
Incrustation,  682. 
Indicating  Ideal  engines,  306. 
Indicator,  applying  pencil  to  card, 

367. 

attaching  the  card,  366. 
benefit  from  use  of,  364. 
combined  diagram,  362. 
connecting  to  cylinder, 

346. 

construction  of,  345. 
diagram    analysis,    347, 

377. 
"  ammonia 

pump,  373. 
"  Ball  engine, 

374. 


106G 


INDEX. 


Indicator    diagram  condensing 

engine,  352. 
Dickson  en- 
gine, 376. 
Eclipse  refrig. 
mach.,   371. 
"  Harrisburg 

Ideal,  369. 
H  Harrisburg 

Standard, 
370. 
measuring, 

346. 

"  Russell  en- 

gine, 367. 
eccentric  card, 

362. 
"        effect  of  changing  valve 

stem,  364. 

lf      "     leakage,  363. 
of  what  use,  649. 
operation  of,  346. 
selecting  spring,  366. 
springs,  346. 

"         attention       re- 
quired,   366. 
steam  chest  cards,  359. 
stroke  cards,  358. 
"          tension  of  drum  spring, 

366. 

"         to  take   a  diagram,  365. 
Injector,  and  inspirator,  591. 

"        capacity,         horsepower, 

etc.,  601. 

height  of  lift,  671. 
piping  an,  594. 
selection  of,  428. 
starting  pressure,  597. 
the  Peuberthy,  600. 
the  World,  593. 
to  discern  cause  of  diffi- 
culties, 599. 

"       to  test  for  leaks,  601. 
Injection,  auxiliary,  259. 
Inspirator,  the  Hancock,  597. 

"          to  clean,  598. 
Iron,  weight  of  square  and  round, 

488. 
JOURNALS,  heating  of,  193. 


1C 

it 


KNOCKING  in  engines,    189,  119 
LAP,  definition  of,  654. 
Lead,  adjusting  the,  319. 
"      definition  of,  653. 
"      inside,  666. 
"      with  link  motion,  318. 
Lever,  the,  768. 
Liquids,  friction  of,  564. 
Lost  motion,  taking  up,  652. 
Low  water,  436. 
Lubrication,  186. 

adhesion  1046. 
cohesiveness,  1045. 
cylinder    And     valve, 

1049. 
"  essent  als  of  cylinder, 

1051 
"  number    of  drops    of 

oil,  1052. 

"  of    refrigerating    ma- 

chinery, 1053. 

"  petroleum    oils,  1046. 

(t  reliable  test,  1053. 

"  theory  of,  1045. 

"  to  detect  insufficient, 

1052. 
te  wet  steam,   effect  of, 

1050. 

lubricators,  automatic,  310. 
"  sight  feed,  312. 

MAIN  bearing,  care  of,  190,  192. 
Mclntosh     and    Seymour    engine, 

29o. 

Mechanical  refrigeration,  619,  635. 
Melting  points  of  metals,  687. 
Metric  system,  809. 
Momentum,  671. 
Mud  drum,  648. 
PETROLEUM  in  boilers,  442. 
Pipe,  blowoff,  429. 

cutting  to  order,  675. 
dry,  what  it  is,  431. 
expansion    of   wrought  iron, 

485. 

feed,  area  of,  427. 
length   required  to  condense 

steam,  47£. 

Pipes.  looa,iiori  of  steam,  428. 
"      capacities  of,  485,  1039. 


INDEX. 


1067 


Pipes,  contents  in  gallons,  1039. 
"      sizes  of  mai  s  and  branches, 

485. 

"      steam,  785. 
"          "      connecting  up,  429. 
Piping,  simplicity  in  steam,  674. 
Piston,  area,  to  find,  564. 
"        leaking,    to  tell    from  dia- 
gram, 655. 
"         rings,  187. 
"        speed,  275. 

"     for  pumps,  654. 
"        testing  for  leakage,  669. 
Pitch  for  wheels,  704. 
Pohle,  air  lift  system,  807. 
Porter- Allen  engine,  281,  288. 
Power,  definition  of,  274. 

if      rope  transmission  of^  712. 
Pressure,  absolute,  398. 

"        excessive,  effect  of,  452. 
u        in  receiver,  256. 
t(        mean  effective,  349,  351. 
"        test  for  boilers,  447. 
tf        total  average,  275. 
Priming,  effects  of,  329. 
Pump,  arranging  pipe  connections, 

569. 
"      Blake,  555. 

calculating  boiler  for,  580. 

Cameron,  548. 

Deane,  direct  acting,  546. 

duplex,  operation  of,  569. 

formulas,  618. 

Hooker,  553. 

Knowles,  550. 

Lost  motion,  in,  567. 

miscellaneous        questions, 

550-567,  571-580. 
<e      setting    valves    on    duplex, 

567. 

"      taking  care  of,  575. 
"       Worthington  compound,  544. 
QUESTIONS  asked  when  applying 

for  license,  648-671. 
REAUiMER  thermometer,  811. 
Receiver  pressure,  256. 
Refrigeration,  619-640. 

"  air  in  system,  628. 

"  brine  system,  622, 


Refrigeration,      cold    easily   regu- 
lated, 622. 

<{  condenser,  626. 

"  "  pressure, 

624. 

"  direct         expansion, 

623. 

lf,  effect  of  ammonia  on 

pipes,  633. 

"  expansion  coils,  634. 

tc  function     of     pump, 

621. 

tf  instructions  for  oper- 

ating plant,  624. 
leaks  in  pipes,  625. 

"  lubrication     of    ma- 

chine, 632. 

"  oil  in  the  system,  627. 

"  operation    of    appar- 

atus, 620. 

"  principles   of    opera- 

ation,  620. 

ce  process  of,  635. 

"  pump  and  condenser, 

621,636. 

"  rating    of     machine, 

623. 

"  reboilers,  628. 

"  selection  of  oils,  633. 

"  shutting    down    ma- 

chine, 625. 

te  starting  machine,  624. 

(t  steam        condensers, 

627. 

ff  suction  pressure,  625. 

"  test  for  compressor, 

626. 

"  testing  for  water,  631. 

fe  to      charge     system, 

634. 

"  utilizing    the      cold, 

622. 

f<  valves,     location    of, 

624 

"  what  does  the  work, 

621. 

Rocker  shaft,  influence  of,  273,  319. 
Rope,  hoisting,  814. 
"      horsepower  transmitted,  813, 


1068 


INDEX. 


Rope,  proper  diam.  of  sheaves,  813, 

"      speed  of,  813. 

"      to  test  purity  of,  814. 

"      transmission,  systems  of,  812. 

"      working  strain,  813. 
Ropes,  limit  to  number,  813. 

Rules:  — 

air  cylinder,  capacity  of,  801. 
ampere  turns  required,  46. 
amperes,  to  find,  166. 
area  of  safety  valves,  427. 
armature  pall,  63. 
belt,  length  required,  789. 
"     width  required,  789. 
boiler,  distance  between  rows  of 

rivets,  465. 

boiler,  maximum  pitches  of  riv- 
ets, 466. 
boiler,  pitch,  diagonal,  464,  456. 

"       safe     working     pressure, 

477. 

centrifugal  force,  501. 
chimney,  stability  of,  693. 
chorda!  pitch,  699. 
circle  circumference,  788. 
circular  mils,  166. 
circumference  of  gear,  700. 
cylinder,  capacity,  565. 
engine,  duty  of  pumping,  615. 

"        to  increase  p  >wer,  383. 

s(        to  increase  speed,  381. 
factor  of  evaporation,  539. 
gears,  depth  of  tooth,  709. 

"      distance  between  centers, 
711. 

"      horsepower  of,  695,  710. 

"      speed  of,  7LO. 

"      velocity  of,  695. 
heating    surface  in    square  feet, 

539. 
heating    surface     of  water  tube 

boilers,  461. 
horsepower,    boiler     pump    will 

supply,  617. 

horsepower,    of    compound    en- 
gine, 392. 
horsepower    of     noncondensing 

engine,  392. 


horsepower  of  pumping  engine, 

616. 

linear  expansion  of  pipe,  394. 
magnet,  lifting  capacity,  13. 
magnetic  flux  in  maxwells,  63. 
number  of  expansions,  226. 
pinion,  diameter  of,  700. 
pulley,  diameter  of  driven,  789. 
"        effect  of  arc  of  contact, 

791,  795. 

"        effect    of     distance    be- 
tween, 797. 

"        effect  of  size,  790. 
"        revolution  of  driver,  788. 
"        speed  of  driven,  788. 
"        velocity  of  driver,  788. 
pump,   capacity  to   feed   boiler, 

616. 

"       discharge  nozzle,  607. 
u      maximum  lift,  618. 
' '      pressure  can  work  against, 

604. 

"      size  to  feed  boiler,  613. 
"      suction  pipe,  size  of,  608. 
"      to  find  diameter  of  piston, 

605. 
"      to    find    horsepower      of 

boiler  required,  606. 
"      to    find     horsepower    re- 
quired in  a,  605. 
"      to  find  steam  pressure  re- 
quired, 604. 
proportional     radius     of    gears, 

700. 

reinforcing  ring,  width  of,  541. 
relative  velocity  of  pinion,  700. 
revolutions  of   wheel  or  pinion, 

700.» 

rivets,  shearing  strength,  537. 
safe  stress  for  tooth,  705. 
"     working  pressure,  536. 
«  "    "        "          A.S.M.E. 

rule,  537. 

shafting,  horsepower  of,  697. 
steam  and  water  pistons,   sizes, 

603. 

gteam  pipe  size  required,  394. 
"      u  §ed  with  steam  jets,  542 


INDEX. 


1069 


Rules:  — 

Steam,  weight  discharged,  540. 
strain  allowed  on  stay,  475. 
strength  of  boiler  joint,  537. 
strength  of  diagonal  stays,  476. 

"  of  stayed  flat  surfaces, 
thickness  of  plate  for  shell,  463. 
train  of  wheels  and  pinions,  699. 
valves,  safety,  center  of  gravity 

of  lever,  499. 
valves,  safety,  pressure  to  raise 

weight,  498. 
valves,  safety,  U.  S.  Gov.  rule, 

427. 
valves,  safety,  weight  required, 

497. 

volts  lost,  to  find,  166. 
water,  area  for  given  discharge, 

611. 
"       consumption    of    engine, 

395. 

"      discharge  under  head,  609. 
"      elevated  per  minute,  565. 
"      flow  in  pipe,  611. 
"      gallons  delivered  per  min- 
ute, 603. 

"      given  press,   to  find  dis- 
charge, 610. 
"      head,  in  feet  corresp.   to 

friction,  613. 
lt      horsepower    required    to 

elevate, 563. 
"      pounds    per     horsepower 

for  boiler,  618.. 

"      velocity    for    given    dis- 
charge, 609. 

"       weight  of  column,  565. 
weight  of  fly-wheels,  276. 
wheel,  diameter  of,  699. 

t(  il  for  given  pitch, 

703. 

"      number  of  teeth,  697. 
"       pitch  of,  698. 
"    proportional    velocity    of, 

701. 

wire,  size  of,  166. 
Russell  engine,  setting  single  valve, 

277. 
SAFETY  at  high  pressure,  401. 


Scale,  effect  of,  440. 

"      how  to  remove,  655. 
Screw-cutting,  713. 
Shafting,  lining  up,  672. 
Sheet  iron,  weight,  712. 
Slide  valve,  changing  cutoff,  666. 

"        "         fitting,  191. 
Smoke,  419. 
Soda,  carbonate,  441. 
Something  for  nothing,  688. 
Staybolt,  grip,  of  copper,  474. 
Steam  coils,  480,481. 
Steam,  consumption    in    practice, 

180. 
"  u  of  an  engine, 

834. 

"      dome,  430. 

"      effect  of  compression,  399. 
"      generating,  332. 
"      gage,  what  it  indicates,  399. 
tf      high  pressure,  332. 
"      method  of  condensing,  233. 
"      pipe  for  heating  water,  478. 
"      pipes,  loss  of  heat  irom,  391. 

"      size  of,  275. 
"      plants,  economy  in,  327. 
"     power    plant,    operating    a, 

325. 
"         "  "        taking  charge 

of,  323. 

"      pressure  of,  400. 
"      properties  of  saturated,  330. 
"      pump,  the,  544. 
"      temperature    and    pressure, 

684. 

"      used  with  steam  jets,  542. 
"      using  full  stroke,  335. 
"      velocity  in  engine,  394. 
"  "        of  escape,  496. 

€(      water  required  to  condense, 

236. 
'.'      weight  condensed  in  heating 

water,  479. 
"         "      discharged  per  second, 

540. 
"      where  the  force  comes  from, 

398. 

"      why  valuable,  652. 
Steel  stacks,  weight  of,  694. 


1070 


INDEX. 


Stufflngboxes,  188. 
Sulphate  of  lime,  441. 

Tables:  — 

actual   ratios   of  expansion,  928. 
air  required  for  rock  drills,  933, 

934. 
ammonia  compressor,  902. 

"        gas   for  one   ton  refri- 
geration, 898. 
t(        horsepower  to  compress 

one  cu.  ft.  901. 
"        properties  of,  899. 
amperes,  per  lamp*  173. 
amperes,  per  motor,  169,  170. 
arcs    of    contact,    useful    effect, 

795. 
areas   of  circular  segments,  935, 

936. 

area  of  safety  valve,  495. 
boiler,  energy  stored  in,  448. 
boiling   points    of    various    sub- 
stances, 907. 
brick  required  for  boiler  setting, 

522. 
brine     solution,     properties     of, 

900. 

capacity    and  horsepower  of  in- 
jector, 601. 

"  of    reservoirs    in    gal- 

lons, 910. 
"  of    square    cistern    in 

gallons,  585. 
"  of    tanks    in    gallons, 

584. 

carbonic  acid,  properties  of,  900. 
carrying  capacities  of  wires,  99- 

102. 

coal,  per  sq.  ft.  of  grate,  908. 
condenser,  power  gained  by  ad- 
ding a,  923. 
"  water    required    for, 

237. 
contents  of  cylinder  for  one  foot 

length,  801. 

te  of  pipes  and  tanks,  1039. 

Corliss  engines,  sizes  and  dimen- 
sions, 926. 
cost  of  coal  per  annum,  909. 


Tables:— 

cost  of  water  per   1000   gallons 

587. 
decimal  equivalent  of   an    inch, 

583. 
diameters,    circumferences,    and 

areas  of  circles,  895. 
dimensions    of    steam,    gas   and 

water  pipe,  486. 
electric  light  conductors,  176. 
feed  water     required    by    small 

engines,  676. 

flues,  safe  pressure  for,  952. 
fusible    plugs,   melting     points, 

907. 
heating  surface   in   square   feet, 

501. 
f(  tf         per   horsepower, 

403. 
heat  in  water  between   32°  and 

212°,  602. 
hoisting  rope,  strength  and  price, 

812,919. 
horsepower    for       one      pound 

M.E.P.,  924. 

"  of   slide     valve  en- 

gines, 922. 

ft  per  ton  of  refrigera- 

tion, 904 

"  "    "     of  belts,  796. 

"  "    «     of  gear 

wheels, 
696. 

•'  "    "     of     manilla, 

rope, 
712, 
813. 
•'  "    "     of     shafting 

697. 
t€  "    f(     of  wire  rope 

715. 

hyperbolic  logarithms,  892. 
ignition  points   of  various   sub- 
stances, 589. 

incandescent  wiring,  161,  162. 
latent  heat  of  liquids,  583. 
loss  by  friction  in  water  pipes, 
588. 


INDEX. 


1071 


Tables:— 

Loss,  from  uncovered  pipes,  391. 
mean    absolute    pressures,    925. 
melting    points    of    metals    and 

solids,  687-907. 
piston  speed  ft.  per  min.,  912. 
pipes  and  tanks,  cap'y,  1039. 
pitch  of  wheels,  706,  704. 
pneumatic  tools,  933. 
pressure    in    boilers  built   since 

1872,  516-519. 
"      of  water    due    to    height, 

582. 
"      required  to  start  injector, 

597. 
properties    of    saturated    steam, 

330,  913. 
proportions  of  boiler  joints,  467- 

472,  946. 
ff  of  parts  of  engines, 

275. 

pull  of  belt  one  inch  wide,  799. 
pump,  boiler  feed,  397. 
pumps,  capacity  of  duplex,  893. 
"  "          of    low      pres- 

sure, 894. 
<f          sizes    of    cylinders   for 

compound,  923,  927. 
speed    and  capacity   of 

centrifugal,  927. 
rise  of  safety  valve,  494. 
riveted  seams,  measurement  of, 

944-951. 
{(      specifications  for, 

937. 

ropes  for  inclined  planes,  920. 
"      iron    and   steel    transmis- 
sion, 918. 
ft      transmission  of  power,  by, 

921. 
•aving    by    heating  feed    water, 

680. 
showing     how     water    may    be 

wasted,  589. 
sizes  of  chimneys,  692. 
Bteam  consumption  in  N    C.  en- 
gines, 183. 

•ulphur  dioxide,   properties   of, 
898. 


Tables:— 

thermometers,  903. 
total  heat  in  steam,  677. 
tubular  boilers,  930,  931,  932. 
U.  8.    gallons  in  given   number  of 

cu.  ft.,  586. 
volts,   lost    for  per  cent  of   drop, 

171,  172. 

wages,  table  of,  929. 
weight  and  strength  of   iron  bolts, 

906. 
weight  of  engine,  273. 

"      "  rivets  and  bolts,  905. 
'       "  round  iron,  per  foot,  488. 
e      "  steel  smoke  stacks,  694. 
<      "  water,  585. 
'    per  square  foot  of  sheet  iron. 

712. 
weights  of  feed  water  and  of  steam, 

677. 
wire    gages,    difference    between, 

175. 

"        u      for  110-volt  lamps,  37. 
<f        "      weight  and  meas.    of 

water  proof,  174. 
Tanks,  capacity  of,  584. 
Tannate  of  soda,  442. 
Teeth  of  wheels,  705,  709. 
Theoretical  curve,  353. 
Thermometers,  811. 
Tubes  or  flues,  materials  for,  481. 
lf      "     "       seamless,  482. 
"      '*     "      sizes,  482. 
USEFUL  INFORMATION,  1023. 
VACUUM,  effect  on  economy,  233. 
"  how  maintained,  653. 

"          in  condenser,  236.  * 
Valve,  check,  429. 

"      cutoff,  setting,  266. 

"      flat  riding  cutoff,  268. 

"      gear,  double  eccentric,  215, 

222. 
"      leaking,    how    to  discover, 

655. 
"      motion,  direct  and  indirect, 

668. 

"      plain  slide,  function  of,  320. 
"      piston,  riding  cutoff,  263. 
«        "         type,  setting,  261. 


1072 


INDEX. 


Valve,  safety,  426,  491,  499. 
"        "        area  of,  495. 
(t      proportion  of  lever,  670. 
"      rise  of,  494. 
"      setting  for  engineers,  318. 
"  "      plain  slide,  318,,  320. 

"  "      riding     cutoff    with 

governor,  272. 

"  "      slide    with  link-mo- 

tion, 313. 

"      slide,  to  set  in  a  hurry,  388. 
"      spindle,    adjusting    length, 

319. 

'*      stem,  length  of,  668. 
Ventilation,  data  relating  to,  484. 
Water,  681,  1024. 

"       columns,  489,  515. 

»<      cost  of,  587. 

"       distilled  for  boilers,  439. 

"      evaporated    per    pound  of 

coal,  650. 

tf       for  use  in  boilers,  438. 
(l      height  of  column  for  given 
press,  580. 


Water,  how  may  be  wasted,  589. 
"        kinds  of  impurities,  438. 
"        loss  by  friction  in   pipes, 

588. 
"        maximum        evaporat  on, 

421. 
tf        meter^    the    Worthington, 

681.' 
"        pressure    due    to     height, 

582,  585. 

te  "        of  column,  565. 

"        required  by  boiler,  565. 
"        steam    required    to     heat, 

478. 

"        weight  of,  564,  585. 
Westinghouse  compound  engine, 

307. 

Wheel  gearing,  698. 
Wire      rope,      transmission      of 

power,  715. 

Wood,  weight  equal  to  coal,  651. 
Work,  definition  of,  274. 
Worm  screw,  708. 


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LIBRARY.    BRANCH    OF    THE    COLLEGE    OF    AGRICULTURE 


137 

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TJ151 

Handbook 

on 

T8 

engineer!!* 

5* 

1907 

• 

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